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fold-const.c

/* Fold a constant sub-tree into a single node for C-compiler
   Copyright (C) 1987, 88, 92-98, 1999 Free Software Foundation, Inc.

This file is part of GNU CC.

GNU CC is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 2, or (at your option)
any later version.

GNU CC is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
GNU General Public License for more details.

You should have received a copy of the GNU General Public License
along with GNU CC; see the file COPYING.  If not, write to
the Free Software Foundation, 59 Temple Place - Suite 330,
Boston, MA 02111-1307, USA.  */

/*@@ This file should be rewritten to use an arbitrary precision
  @@ representation for "struct tree_int_cst" and "struct tree_real_cst".
  @@ Perhaps the routines could also be used for bc/dc, and made a lib.
  @@ The routines that translate from the ap rep should
  @@ warn if precision et. al. is lost.
  @@ This would also make life easier when this technology is used
  @@ for cross-compilers.  */


/* The entry points in this file are fold, size_int_wide, size_binop
   and force_fit_type.

   fold takes a tree as argument and returns a simplified tree.

   size_binop takes a tree code for an arithmetic operation
   and two operands that are trees, and produces a tree for the
   result, assuming the type comes from `sizetype'.

   size_int takes an integer value, and creates a tree constant
   with type from `sizetype'.

   force_fit_type takes a constant and prior overflow indicator, and
   forces the value to fit the type.  It returns an overflow indicator.  */

#include "config.h"
#include "system.h"
#include <setjmp.h>
#include "flags.h"
#include "tree.h"
#include "toplev.h"

/* Handle floating overflow for `const_binop'.  */
static jmp_buf float_error;

static void encode            PROTO((HOST_WIDE_INT *,
                               HOST_WIDE_INT, HOST_WIDE_INT));
static void decode            PROTO((HOST_WIDE_INT *,
                               HOST_WIDE_INT *, HOST_WIDE_INT *));
int div_and_round_double      PROTO((enum tree_code, int, HOST_WIDE_INT,
                               HOST_WIDE_INT, HOST_WIDE_INT,
                               HOST_WIDE_INT, HOST_WIDE_INT *,
                               HOST_WIDE_INT *, HOST_WIDE_INT *,
                               HOST_WIDE_INT *));
static int split_tree         PROTO((tree, enum tree_code, tree *,
                               tree *, int *));
static tree int_const_binop   PROTO((enum tree_code, tree, tree, int, int));
static tree const_binop       PROTO((enum tree_code, tree, tree, int));
static tree fold_convert      PROTO((tree, tree));
static enum tree_code invert_tree_comparison PROTO((enum tree_code));
static enum tree_code swap_tree_comparison PROTO((enum tree_code));
static int truth_value_p      PROTO((enum tree_code));
static int operand_equal_for_comparison_p PROTO((tree, tree, tree));
static int twoval_comparison_p      PROTO((tree, tree *, tree *, int *));
static tree eval_subst        PROTO((tree, tree, tree, tree, tree));
static tree omit_one_operand  PROTO((tree, tree, tree));
static tree pedantic_omit_one_operand PROTO((tree, tree, tree));
static tree distribute_bit_expr PROTO((enum tree_code, tree, tree, tree));
static tree make_bit_field_ref      PROTO((tree, tree, int, int, int));
static tree optimize_bit_field_compare PROTO((enum tree_code, tree,
                                    tree, tree));
static tree decode_field_reference PROTO((tree, int *, int *,
                                enum machine_mode *, int *,
                                int *, tree *, tree *));
static int all_ones_mask_p    PROTO((tree, int));
static int simple_operand_p   PROTO((tree));
static tree range_binop       PROTO((enum tree_code, tree, tree, int,
                               tree, int));
static tree make_range        PROTO((tree, int *, tree *, tree *));
static tree build_range_check PROTO((tree, tree, int, tree, tree));
static int merge_ranges       PROTO((int *, tree *, tree *, int, tree, tree,
                               int, tree, tree));
static tree fold_range_test   PROTO((tree));
static tree unextend          PROTO((tree, int, int, tree));
static tree fold_truthop      PROTO((enum tree_code, tree, tree, tree));
static tree strip_compound_expr PROTO((tree, tree));
static int multiple_of_p      PROTO((tree, tree, tree));
static tree constant_boolean_node PROTO((int, tree));

#ifndef BRANCH_COST
#define BRANCH_COST 1
#endif

/* Suppose A1 + B1 = SUM1, using 2's complement arithmetic ignoring overflow.
   Suppose A, B and SUM have the same respective signs as A1, B1, and SUM1.
   Then this yields nonzero if overflow occurred during the addition.
   Overflow occurs if A and B have the same sign, but A and SUM differ in sign.
   Use `^' to test whether signs differ, and `< 0' to isolate the sign.  */
#define overflow_sum_sign(a, b, sum) ((~((a) ^ (b)) & ((a) ^ (sum))) < 0)

/* To do constant folding on INTEGER_CST nodes requires two-word arithmetic.
   We do that by representing the two-word integer in 4 words, with only
   HOST_BITS_PER_WIDE_INT/2 bits stored in each word, as a positive number.  */

#define LOWPART(x) \
  ((x) & (((unsigned HOST_WIDE_INT) 1 << (HOST_BITS_PER_WIDE_INT/2)) - 1))
#define HIGHPART(x) \
  ((unsigned HOST_WIDE_INT) (x) >> HOST_BITS_PER_WIDE_INT/2)
#define BASE ((unsigned HOST_WIDE_INT) 1 << HOST_BITS_PER_WIDE_INT/2)

/* Unpack a two-word integer into 4 words.
   LOW and HI are the integer, as two `HOST_WIDE_INT' pieces.
   WORDS points to the array of HOST_WIDE_INTs.  */

static void
encode (words, low, hi)
     HOST_WIDE_INT *words;
     HOST_WIDE_INT low, hi;
{
  words[0] = LOWPART (low);
  words[1] = HIGHPART (low);
  words[2] = LOWPART (hi);
  words[3] = HIGHPART (hi);
}

/* Pack an array of 4 words into a two-word integer.
   WORDS points to the array of words.
   The integer is stored into *LOW and *HI as two `HOST_WIDE_INT' pieces.  */

static void
decode (words, low, hi)
     HOST_WIDE_INT *words;
     HOST_WIDE_INT *low, *hi;
{
  *low = words[0] | words[1] * BASE;
  *hi = words[2] | words[3] * BASE;
}

/* Make the integer constant T valid for its type
   by setting to 0 or 1 all the bits in the constant
   that don't belong in the type.
   Yield 1 if a signed overflow occurs, 0 otherwise.
   If OVERFLOW is nonzero, a signed overflow has already occurred
   in calculating T, so propagate it.

   Make the real constant T valid for its type by calling CHECK_FLOAT_VALUE,
   if it exists.  */

int
force_fit_type (t, overflow)
     tree t;
     int overflow;
{
  HOST_WIDE_INT low, high;
  register int prec;

  if (TREE_CODE (t) == REAL_CST)
    {
#ifdef CHECK_FLOAT_VALUE
      CHECK_FLOAT_VALUE (TYPE_MODE (TREE_TYPE (t)), TREE_REAL_CST (t),
                   overflow);
#endif
      return overflow;
    }

  else if (TREE_CODE (t) != INTEGER_CST)
    return overflow;

  low = TREE_INT_CST_LOW (t);
  high = TREE_INT_CST_HIGH (t);

  if (POINTER_TYPE_P (TREE_TYPE (t)))
    prec = POINTER_SIZE;
  else
    prec = TYPE_PRECISION (TREE_TYPE (t));

  /* First clear all bits that are beyond the type's precision.  */

  if (prec == 2 * HOST_BITS_PER_WIDE_INT)
    ;
  else if (prec > HOST_BITS_PER_WIDE_INT)
    {
      TREE_INT_CST_HIGH (t)
      &= ~((HOST_WIDE_INT) (-1) << (prec - HOST_BITS_PER_WIDE_INT));
    }
  else
    {
      TREE_INT_CST_HIGH (t) = 0;
      if (prec < HOST_BITS_PER_WIDE_INT)
      TREE_INT_CST_LOW (t) &= ~((HOST_WIDE_INT) (-1) << prec);
    }

  /* Unsigned types do not suffer sign extension or overflow.  */
  if (TREE_UNSIGNED (TREE_TYPE (t)))
    return overflow;

  /* If the value's sign bit is set, extend the sign.  */
  if (prec != 2 * HOST_BITS_PER_WIDE_INT
      && (prec > HOST_BITS_PER_WIDE_INT
        ? (TREE_INT_CST_HIGH (t)
           & ((HOST_WIDE_INT) 1 << (prec - HOST_BITS_PER_WIDE_INT - 1)))
        : TREE_INT_CST_LOW (t) & ((HOST_WIDE_INT) 1 << (prec - 1))))
    {
      /* Value is negative:
       set to 1 all the bits that are outside this type's precision.  */
      if (prec > HOST_BITS_PER_WIDE_INT)
      {
        TREE_INT_CST_HIGH (t)
          |= ((HOST_WIDE_INT) (-1) << (prec - HOST_BITS_PER_WIDE_INT));
      }
      else
      {
        TREE_INT_CST_HIGH (t) = -1;
        if (prec < HOST_BITS_PER_WIDE_INT)
          TREE_INT_CST_LOW (t) |= ((HOST_WIDE_INT) (-1) << prec);
      }
    }

  /* Yield nonzero if signed overflow occurred.  */
  return
    ((overflow | (low ^ TREE_INT_CST_LOW (t)) | (high ^ TREE_INT_CST_HIGH (t)))
     != 0);
}

/* Add two doubleword integers with doubleword result.
   Each argument is given as two `HOST_WIDE_INT' pieces.
   One argument is L1 and H1; the other, L2 and H2.
   The value is stored as two `HOST_WIDE_INT' pieces in *LV and *HV.  */

int
add_double (l1, h1, l2, h2, lv, hv)
     HOST_WIDE_INT l1, h1, l2, h2;
     HOST_WIDE_INT *lv, *hv;
{
  HOST_WIDE_INT l, h;

  l = l1 + l2;
  h = h1 + h2 + ((unsigned HOST_WIDE_INT) l < l1);

  *lv = l;
  *hv = h;
  return overflow_sum_sign (h1, h2, h);
}

/* Negate a doubleword integer with doubleword result.
   Return nonzero if the operation overflows, assuming it's signed.
   The argument is given as two `HOST_WIDE_INT' pieces in L1 and H1.
   The value is stored as two `HOST_WIDE_INT' pieces in *LV and *HV.  */

int
neg_double (l1, h1, lv, hv)
     HOST_WIDE_INT l1, h1;
     HOST_WIDE_INT *lv, *hv;
{
  if (l1 == 0)
    {
      *lv = 0;
      *hv = - h1;
      return (*hv & h1) < 0;
    }
  else
    {
      *lv = - l1;
      *hv = ~ h1;
      return 0;
    }
}

/* Multiply two doubleword integers with doubleword result.
   Return nonzero if the operation overflows, assuming it's signed.
   Each argument is given as two `HOST_WIDE_INT' pieces.
   One argument is L1 and H1; the other, L2 and H2.
   The value is stored as two `HOST_WIDE_INT' pieces in *LV and *HV.  */

int
mul_double (l1, h1, l2, h2, lv, hv)
     HOST_WIDE_INT l1, h1, l2, h2;
     HOST_WIDE_INT *lv, *hv;
{
  HOST_WIDE_INT arg1[4];
  HOST_WIDE_INT arg2[4];
  HOST_WIDE_INT prod[4 * 2];
  register unsigned HOST_WIDE_INT carry;
  register int i, j, k;
  HOST_WIDE_INT toplow, tophigh, neglow, neghigh;

  encode (arg1, l1, h1);
  encode (arg2, l2, h2);

  bzero ((char *) prod, sizeof prod);

  for (i = 0; i < 4; i++)
    {
      carry = 0;
      for (j = 0; j < 4; j++)
      {
        k = i + j;
        /* This product is <= 0xFFFE0001, the sum <= 0xFFFF0000.  */
        carry += arg1[i] * arg2[j];
        /* Since prod[p] < 0xFFFF, this sum <= 0xFFFFFFFF.  */
        carry += prod[k];
        prod[k] = LOWPART (carry);
        carry = HIGHPART (carry);
      }
      prod[i + 4] = carry;
    }

  decode (prod, lv, hv);      /* This ignores prod[4] through prod[4*2-1] */

  /* Check for overflow by calculating the top half of the answer in full;
     it should agree with the low half's sign bit.  */
  decode (prod+4, &toplow, &tophigh);
  if (h1 < 0)
    {
      neg_double (l2, h2, &neglow, &neghigh);
      add_double (neglow, neghigh, toplow, tophigh, &toplow, &tophigh);
    }
  if (h2 < 0)
    {
      neg_double (l1, h1, &neglow, &neghigh);
      add_double (neglow, neghigh, toplow, tophigh, &toplow, &tophigh);
    }
  return (*hv < 0 ? ~(toplow & tophigh) : toplow | tophigh) != 0;
}

/* Shift the doubleword integer in L1, H1 left by COUNT places
   keeping only PREC bits of result.
   Shift right if COUNT is negative.
   ARITH nonzero specifies arithmetic shifting; otherwise use logical shift.
   Store the value as two `HOST_WIDE_INT' pieces in *LV and *HV.  */

void
lshift_double (l1, h1, count, prec, lv, hv, arith)
     HOST_WIDE_INT l1, h1, count;
     int prec;
     HOST_WIDE_INT *lv, *hv;
     int arith;
{
  if (count < 0)
    {
      rshift_double (l1, h1, - count, prec, lv, hv, arith);
      return;
    }
  
#ifdef SHIFT_COUNT_TRUNCATED
  if (SHIFT_COUNT_TRUNCATED)
    count %= prec;
#endif

  if (count >= HOST_BITS_PER_WIDE_INT)
    {
      *hv = (unsigned HOST_WIDE_INT) l1 << (count - HOST_BITS_PER_WIDE_INT);
      *lv = 0;
    }
  else
    {
      *hv = (((unsigned HOST_WIDE_INT) h1 << count)
           | ((unsigned HOST_WIDE_INT) l1 >> (HOST_BITS_PER_WIDE_INT - count - 1) >> 1));
      *lv = (unsigned HOST_WIDE_INT) l1 << count;
    }
}

/* Shift the doubleword integer in L1, H1 right by COUNT places
   keeping only PREC bits of result.  COUNT must be positive.
   ARITH nonzero specifies arithmetic shifting; otherwise use logical shift.
   Store the value as two `HOST_WIDE_INT' pieces in *LV and *HV.  */

void
rshift_double (l1, h1, count, prec, lv, hv, arith)
     HOST_WIDE_INT l1, h1, count;
     int prec;
     HOST_WIDE_INT *lv, *hv;
     int arith;
{
  unsigned HOST_WIDE_INT signmask;
  signmask = (arith
            ? -((unsigned HOST_WIDE_INT) h1 >> (HOST_BITS_PER_WIDE_INT - 1))
            : 0);

#ifdef SHIFT_COUNT_TRUNCATED
  if (SHIFT_COUNT_TRUNCATED)
    count %= prec;
#endif

  if (count >= HOST_BITS_PER_WIDE_INT)
    {
      *hv = signmask;
      *lv = ((signmask << (2 * HOST_BITS_PER_WIDE_INT - count - 1) << 1)
           | ((unsigned HOST_WIDE_INT) h1 >> (count - HOST_BITS_PER_WIDE_INT)));
    }
  else
    {
      *lv = (((unsigned HOST_WIDE_INT) l1 >> count)
           | ((unsigned HOST_WIDE_INT) h1 << (HOST_BITS_PER_WIDE_INT - count - 1) << 1));
      *hv = ((signmask << (HOST_BITS_PER_WIDE_INT - count))
           | ((unsigned HOST_WIDE_INT) h1 >> count));
    }
}

/* Rotate the doubleword integer in L1, H1 left by COUNT places
   keeping only PREC bits of result.
   Rotate right if COUNT is negative.
   Store the value as two `HOST_WIDE_INT' pieces in *LV and *HV.  */

void
lrotate_double (l1, h1, count, prec, lv, hv)
     HOST_WIDE_INT l1, h1, count;
     int prec;
     HOST_WIDE_INT *lv, *hv;
{
  HOST_WIDE_INT s1l, s1h, s2l, s2h;

  count %= prec;
  if (count < 0)
    count += prec;

  lshift_double (l1, h1, count, prec, &s1l, &s1h, 0);
  rshift_double (l1, h1, prec - count, prec, &s2l, &s2h, 0);
  *lv = s1l | s2l;
  *hv = s1h | s2h;
}

/* Rotate the doubleword integer in L1, H1 left by COUNT places
   keeping only PREC bits of result.  COUNT must be positive.
   Store the value as two `HOST_WIDE_INT' pieces in *LV and *HV.  */

void
rrotate_double (l1, h1, count, prec, lv, hv)
     HOST_WIDE_INT l1, h1, count;
     int prec;
     HOST_WIDE_INT *lv, *hv;
{
  HOST_WIDE_INT s1l, s1h, s2l, s2h;

  count %= prec;
  if (count < 0)
    count += prec;

  rshift_double (l1, h1, count, prec, &s1l, &s1h, 0);
  lshift_double (l1, h1, prec - count, prec, &s2l, &s2h, 0);
  *lv = s1l | s2l;
  *hv = s1h | s2h;
}

/* Divide doubleword integer LNUM, HNUM by doubleword integer LDEN, HDEN
   for a quotient (stored in *LQUO, *HQUO) and remainder (in *LREM, *HREM).
   CODE is a tree code for a kind of division, one of
   TRUNC_DIV_EXPR, FLOOR_DIV_EXPR, CEIL_DIV_EXPR, ROUND_DIV_EXPR
   or EXACT_DIV_EXPR
   It controls how the quotient is rounded to a integer.
   Return nonzero if the operation overflows.
   UNS nonzero says do unsigned division.  */

int
div_and_round_double (code, uns,
                  lnum_orig, hnum_orig, lden_orig, hden_orig,
                  lquo, hquo, lrem, hrem)
     enum tree_code code;
     int uns;
     HOST_WIDE_INT lnum_orig, hnum_orig; /* num == numerator == dividend */
     HOST_WIDE_INT lden_orig, hden_orig; /* den == denominator == divisor */
     HOST_WIDE_INT *lquo, *hquo, *lrem, *hrem;
{
  int quo_neg = 0;
  HOST_WIDE_INT num[4 + 1];   /* extra element for scaling.  */
  HOST_WIDE_INT den[4], quo[4];
  register int i, j;
  unsigned HOST_WIDE_INT work;
  register unsigned HOST_WIDE_INT carry = 0;
  HOST_WIDE_INT lnum = lnum_orig;
  HOST_WIDE_INT hnum = hnum_orig;
  HOST_WIDE_INT lden = lden_orig;
  HOST_WIDE_INT hden = hden_orig;
  int overflow = 0;

  if ((hden == 0) && (lden == 0))
    overflow = 1, lden = 1;

  /* calculate quotient sign and convert operands to unsigned.  */
  if (!uns) 
    {
      if (hnum < 0)
      {
        quo_neg = ~ quo_neg;
        /* (minimum integer) / (-1) is the only overflow case.  */
        if (neg_double (lnum, hnum, &lnum, &hnum) && (lden & hden) == -1)
          overflow = 1;
      }
      if (hden < 0) 
      {
        quo_neg = ~ quo_neg;
        neg_double (lden, hden, &lden, &hden);
      }
    }

  if (hnum == 0 && hden == 0)
    {                   /* single precision */
      *hquo = *hrem = 0;
      /* This unsigned division rounds toward zero.  */
      *lquo = lnum / (unsigned HOST_WIDE_INT) lden;
      goto finish_up;
    }

  if (hnum == 0)
    {                   /* trivial case: dividend < divisor */
      /* hden != 0 already checked.  */
      *hquo = *lquo = 0;
      *hrem = hnum;
      *lrem = lnum;
      goto finish_up;
    }

  bzero ((char *) quo, sizeof quo);

  bzero ((char *) num, sizeof num); /* to zero 9th element */
  bzero ((char *) den, sizeof den);

  encode (num, lnum, hnum); 
  encode (den, lden, hden);

  /* Special code for when the divisor < BASE.  */
  if (hden == 0 && lden < BASE)
    {
      /* hnum != 0 already checked.  */
      for (i = 4 - 1; i >= 0; i--)
      {
        work = num[i] + carry * BASE;
        quo[i] = work / (unsigned HOST_WIDE_INT) lden;
        carry = work % (unsigned HOST_WIDE_INT) lden;
      }
    }
  else
    {
      /* Full double precision division,
       with thanks to Don Knuth's "Seminumerical Algorithms".  */
    int num_hi_sig, den_hi_sig;
    unsigned HOST_WIDE_INT quo_est, scale;

    /* Find the highest non-zero divisor digit.  */
    for (i = 4 - 1; ; i--)
      if (den[i] != 0) {
      den_hi_sig = i;
      break;
      }

    /* Insure that the first digit of the divisor is at least BASE/2.
       This is required by the quotient digit estimation algorithm.  */

    scale = BASE / (den[den_hi_sig] + 1);
    if (scale > 1) {          /* scale divisor and dividend */
      carry = 0;
      for (i = 0; i <= 4 - 1; i++) {
      work = (num[i] * scale) + carry;
      num[i] = LOWPART (work);
      carry = HIGHPART (work);
      } num[4] = carry;
      carry = 0;
      for (i = 0; i <= 4 - 1; i++) {
      work = (den[i] * scale) + carry;
      den[i] = LOWPART (work);
      carry = HIGHPART (work);
      if (den[i] != 0) den_hi_sig = i;
      }
    }

    num_hi_sig = 4;

    /* Main loop */
    for (i = num_hi_sig - den_hi_sig - 1; i >= 0; i--) {
      /* guess the next quotient digit, quo_est, by dividing the first
       two remaining dividend digits by the high order quotient digit.
       quo_est is never low and is at most 2 high.  */
      unsigned HOST_WIDE_INT tmp;

      num_hi_sig = i + den_hi_sig + 1;
      work = num[num_hi_sig] * BASE + num[num_hi_sig - 1];
      if (num[num_hi_sig] != den[den_hi_sig])
      quo_est = work / den[den_hi_sig];
      else
      quo_est = BASE - 1;

      /* refine quo_est so it's usually correct, and at most one high.   */
      tmp = work - quo_est * den[den_hi_sig];
      if (tmp < BASE
        && den[den_hi_sig - 1] * quo_est > (tmp * BASE + num[num_hi_sig - 2]))
      quo_est--;

      /* Try QUO_EST as the quotient digit, by multiplying the
         divisor by QUO_EST and subtracting from the remaining dividend.
       Keep in mind that QUO_EST is the I - 1st digit.  */

      carry = 0;
      for (j = 0; j <= den_hi_sig; j++)
      {
        work = quo_est * den[j] + carry;
        carry = HIGHPART (work);
        work = num[i + j] - LOWPART (work);
        num[i + j] = LOWPART (work);
        carry += HIGHPART (work) != 0;
      }

      /* if quo_est was high by one, then num[i] went negative and
       we need to correct things.  */

      if (num[num_hi_sig] < carry)
      {
        quo_est--;
        carry = 0;            /* add divisor back in */
        for (j = 0; j <= den_hi_sig; j++)
          {
            work = num[i + j] + den[j] + carry;
            carry = HIGHPART (work);
            num[i + j] = LOWPART (work);
          }
        num [num_hi_sig] += carry;
      }

      /* store the quotient digit.  */
      quo[i] = quo_est;
    }
  }

  decode (quo, lquo, hquo);

 finish_up:
  /* if result is negative, make it so.  */
  if (quo_neg)
    neg_double (*lquo, *hquo, lquo, hquo);

  /* compute trial remainder:  rem = num - (quo * den)  */
  mul_double (*lquo, *hquo, lden_orig, hden_orig, lrem, hrem);
  neg_double (*lrem, *hrem, lrem, hrem);
  add_double (lnum_orig, hnum_orig, *lrem, *hrem, lrem, hrem);

  switch (code)
    {
    case TRUNC_DIV_EXPR:
    case TRUNC_MOD_EXPR:      /* round toward zero */
    case EXACT_DIV_EXPR:      /* for this one, it shouldn't matter */
      return overflow;

    case FLOOR_DIV_EXPR:
    case FLOOR_MOD_EXPR:      /* round toward negative infinity */
      if (quo_neg && (*lrem != 0 || *hrem != 0))   /* ratio < 0 && rem != 0 */
      {
        /* quo = quo - 1;  */
        add_double (*lquo, *hquo, (HOST_WIDE_INT) -1, (HOST_WIDE_INT)  -1,
                  lquo, hquo);
      }
      else return overflow;
      break;

    case CEIL_DIV_EXPR:
    case CEIL_MOD_EXPR:       /* round toward positive infinity */
      if (!quo_neg && (*lrem != 0 || *hrem != 0))  /* ratio > 0 && rem != 0 */
      {
        add_double (*lquo, *hquo, (HOST_WIDE_INT) 1, (HOST_WIDE_INT) 0,
                  lquo, hquo);
      }
      else return overflow;
      break;
    
    case ROUND_DIV_EXPR:
    case ROUND_MOD_EXPR:      /* round to closest integer */
      {
      HOST_WIDE_INT labs_rem = *lrem, habs_rem = *hrem;
      HOST_WIDE_INT labs_den = lden, habs_den = hden, ltwice, htwice;

      /* get absolute values */
      if (*hrem < 0) neg_double (*lrem, *hrem, &labs_rem, &habs_rem);
      if (hden < 0) neg_double (lden, hden, &labs_den, &habs_den);

      /* if (2 * abs (lrem) >= abs (lden)) */
      mul_double ((HOST_WIDE_INT) 2, (HOST_WIDE_INT) 0,
                labs_rem, habs_rem, &ltwice, &htwice);
      if (((unsigned HOST_WIDE_INT) habs_den
           < (unsigned HOST_WIDE_INT) htwice)
          || (((unsigned HOST_WIDE_INT) habs_den
             == (unsigned HOST_WIDE_INT) htwice)
            && ((HOST_WIDE_INT unsigned) labs_den
                < (unsigned HOST_WIDE_INT) ltwice)))
        {
          if (*hquo < 0)
            /* quo = quo - 1;  */
            add_double (*lquo, *hquo,
                    (HOST_WIDE_INT) -1, (HOST_WIDE_INT) -1, lquo, hquo);
          else
            /* quo = quo + 1; */
            add_double (*lquo, *hquo, (HOST_WIDE_INT) 1, (HOST_WIDE_INT) 0,
                    lquo, hquo);
        }
      else return overflow;
      }
      break;

    default:
      abort ();
    }

  /* compute true remainder:  rem = num - (quo * den)  */
  mul_double (*lquo, *hquo, lden_orig, hden_orig, lrem, hrem);
  neg_double (*lrem, *hrem, lrem, hrem);
  add_double (lnum_orig, hnum_orig, *lrem, *hrem, lrem, hrem);
  return overflow;
}

#ifndef REAL_ARITHMETIC
/* Effectively truncate a real value to represent the nearest possible value
   in a narrower mode.  The result is actually represented in the same data
   type as the argument, but its value is usually different.

   A trap may occur during the FP operations and it is the responsibility
   of the calling function to have a handler established.  */

REAL_VALUE_TYPE
real_value_truncate (mode, arg)
     enum machine_mode mode;
     REAL_VALUE_TYPE arg;
{
  return REAL_VALUE_TRUNCATE (mode, arg);
}

#if TARGET_FLOAT_FORMAT == IEEE_FLOAT_FORMAT

/* Check for infinity in an IEEE double precision number.  */

int
target_isinf (x)
     REAL_VALUE_TYPE x;
{
  /* The IEEE 64-bit double format.  */
  union {
    REAL_VALUE_TYPE d;
    struct {
      unsigned sign      :  1;
      unsigned exponent  : 11;
      unsigned mantissa1 : 20;
      unsigned mantissa2;
    } little_endian;
    struct {
      unsigned mantissa2;
      unsigned mantissa1 : 20;
      unsigned exponent  : 11;
      unsigned sign      :  1;
    } big_endian;    
  } u;

  u.d = dconstm1;
  if (u.big_endian.sign == 1)
    {
      u.d = x;
      return (u.big_endian.exponent == 2047
            && u.big_endian.mantissa1 == 0
            && u.big_endian.mantissa2 == 0);
    }
  else
    {
      u.d = x;
      return (u.little_endian.exponent == 2047
            && u.little_endian.mantissa1 == 0
            && u.little_endian.mantissa2 == 0);
    }
}

/* Check whether an IEEE double precision number is a NaN.  */

int
target_isnan (x)
     REAL_VALUE_TYPE x;
{
  /* The IEEE 64-bit double format.  */
  union {
    REAL_VALUE_TYPE d;
    struct {
      unsigned sign      :  1;
      unsigned exponent  : 11;
      unsigned mantissa1 : 20;
      unsigned mantissa2;
    } little_endian;
    struct {
      unsigned mantissa2;
      unsigned mantissa1 : 20;
      unsigned exponent  : 11;
      unsigned sign      :  1;
    } big_endian;    
  } u;

  u.d = dconstm1;
  if (u.big_endian.sign == 1)
    {
      u.d = x;
      return (u.big_endian.exponent == 2047
            && (u.big_endian.mantissa1 != 0
              || u.big_endian.mantissa2 != 0));
    }
  else
    {
      u.d = x;
      return (u.little_endian.exponent == 2047
            && (u.little_endian.mantissa1 != 0
              || u.little_endian.mantissa2 != 0));
    }
}

/* Check for a negative IEEE double precision number.  */

int
target_negative (x)
     REAL_VALUE_TYPE x;
{
  /* The IEEE 64-bit double format.  */
  union {
    REAL_VALUE_TYPE d;
    struct {
      unsigned sign      :  1;
      unsigned exponent  : 11;
      unsigned mantissa1 : 20;
      unsigned mantissa2;
    } little_endian;
    struct {
      unsigned mantissa2;
      unsigned mantissa1 : 20;
      unsigned exponent  : 11;
      unsigned sign      :  1;
    } big_endian;    
  } u;

  u.d = dconstm1;
  if (u.big_endian.sign == 1)
    {
      u.d = x;
      return u.big_endian.sign;
    }
  else
    {
      u.d = x;
      return u.little_endian.sign;
    }
}
#else /* Target not IEEE */

/* Let's assume other float formats don't have infinity.
   (This can be overridden by redefining REAL_VALUE_ISINF.)  */

target_isinf (x)
     REAL_VALUE_TYPE x;
{
  return 0;
}

/* Let's assume other float formats don't have NaNs.
   (This can be overridden by redefining REAL_VALUE_ISNAN.)  */

target_isnan (x)
     REAL_VALUE_TYPE x;
{
  return 0;
}

/* Let's assume other float formats don't have minus zero.
   (This can be overridden by redefining REAL_VALUE_NEGATIVE.)  */

target_negative (x)
     REAL_VALUE_TYPE x;
{
  return x < 0;
}
#endif /* Target not IEEE */

/* Try to change R into its exact multiplicative inverse in machine mode
   MODE.  Return nonzero function value if successful.  */

int
exact_real_inverse (mode, r)
     enum machine_mode mode;
     REAL_VALUE_TYPE *r;
{
  union
    {
      double d;
      unsigned short i[4];
    }x, t, y;
  int i;

  /* Usually disable if bounds checks are not reliable.  */
  if ((HOST_FLOAT_FORMAT != TARGET_FLOAT_FORMAT) && !flag_pretend_float)
    return 0;

  /* Set array index to the less significant bits in the unions, depending
     on the endian-ness of the host doubles.
     Disable if insufficient information on the data structure.  */
#if HOST_FLOAT_FORMAT == UNKNOWN_FLOAT_FORMAT
  return 0;
#else
#if HOST_FLOAT_FORMAT == VAX_FLOAT_FORMAT
#define K 2
#else
#if HOST_FLOAT_FORMAT == IBM_FLOAT_FORMAT
#define K 2
#else
#define K (2 * HOST_FLOAT_WORDS_BIG_ENDIAN)
#endif
#endif
#endif

  if (setjmp (float_error))
    {
      /* Don't do the optimization if there was an arithmetic error.  */
fail:
      set_float_handler (NULL_PTR);
      return 0;
    }
  set_float_handler (float_error);

  /* Domain check the argument.  */
  x.d = *r;
  if (x.d == 0.0)
    goto fail;

#ifdef REAL_INFINITY
  if (REAL_VALUE_ISINF (x.d) || REAL_VALUE_ISNAN (x.d))
    goto fail;
#endif

  /* Compute the reciprocal and check for numerical exactness.
     It is unnecessary to check all the significand bits to determine
     whether X is a power of 2.  If X is not, then it is impossible for
     the bottom half significand of both X and 1/X to be all zero bits.
     Hence we ignore the data structure of the top half and examine only
     the low order bits of the two significands.  */
  t.d = 1.0 / x.d;
  if (x.i[K] != 0 || x.i[K + 1] != 0 || t.i[K] != 0 || t.i[K + 1] != 0)
    goto fail;

  /* Truncate to the required mode and range-check the result.  */
  y.d = REAL_VALUE_TRUNCATE (mode, t.d);
#ifdef CHECK_FLOAT_VALUE
  i = 0;
  if (CHECK_FLOAT_VALUE (mode, y.d, i))
    goto fail;
#endif

  /* Fail if truncation changed the value.  */
  if (y.d != t.d || y.d == 0.0)
    goto fail;

#ifdef REAL_INFINITY
  if (REAL_VALUE_ISINF (y.d) || REAL_VALUE_ISNAN (y.d))
    goto fail;
#endif

  /* Output the reciprocal and return success flag.  */
  set_float_handler (NULL_PTR);
  *r = y.d;
  return 1;
}
#endif /* no REAL_ARITHMETIC */

/* Split a tree IN into a constant and a variable part
   that could be combined with CODE to make IN.
   CODE must be a commutative arithmetic operation.
   Store the constant part into *CONP and the variable in &VARP.
   Return 1 if this was done; zero means the tree IN did not decompose
   this way.

   If CODE is PLUS_EXPR we also split trees that use MINUS_EXPR.
   Therefore, we must tell the caller whether the variable part
   was subtracted.  We do this by storing 1 or -1 into *VARSIGNP.
   The value stored is the coefficient for the variable term.
   The constant term we return should always be added;
   we negate it if necessary.  */

static int
split_tree (in, code, varp, conp, varsignp)
     tree in;
     enum tree_code code;
     tree *varp, *conp;
     int *varsignp;
{
  register tree outtype = TREE_TYPE (in);
  *varp = 0;
  *conp = 0;

  /* Strip any conversions that don't change the machine mode.  */
  while ((TREE_CODE (in) == NOP_EXPR
        || TREE_CODE (in) == CONVERT_EXPR)
       && (TYPE_MODE (TREE_TYPE (in))
           == TYPE_MODE (TREE_TYPE (TREE_OPERAND (in, 0)))))
    in = TREE_OPERAND (in, 0);

  if (TREE_CODE (in) == code
      || (! FLOAT_TYPE_P (TREE_TYPE (in))
        /* We can associate addition and subtraction together
           (even though the C standard doesn't say so)
           for integers because the value is not affected.
           For reals, the value might be affected, so we can't.  */
        && ((code == PLUS_EXPR && TREE_CODE (in) == MINUS_EXPR)
            || (code == MINUS_EXPR && TREE_CODE (in) == PLUS_EXPR))))
    {
      enum tree_code code = TREE_CODE (TREE_OPERAND (in, 0));
      if (code == INTEGER_CST)
      {
        *conp = TREE_OPERAND (in, 0);
        *varp = TREE_OPERAND (in, 1);
        if (TYPE_MODE (TREE_TYPE (*varp)) != TYPE_MODE (outtype)
            && TREE_TYPE (*varp) != outtype)
          *varp = convert (outtype, *varp);
        *varsignp = (TREE_CODE (in) == MINUS_EXPR) ? -1 : 1;
        return 1;
      }
      if (TREE_CONSTANT (TREE_OPERAND (in, 1)))
      {
        *conp = TREE_OPERAND (in, 1);
        *varp = TREE_OPERAND (in, 0);
        *varsignp = 1;
        if (TYPE_MODE (TREE_TYPE (*varp)) != TYPE_MODE (outtype)
            && TREE_TYPE (*varp) != outtype)
          *varp = convert (outtype, *varp);
        if (TREE_CODE (in) == MINUS_EXPR)
          {
            /* If operation is subtraction and constant is second,
             must negate it to get an additive constant.
             And this cannot be done unless it is a manifest constant.
             It could also be the address of a static variable.
             We cannot negate that, so give up.  */
            if (TREE_CODE (*conp) == INTEGER_CST)
            /* Subtracting from integer_zero_node loses for long long.  */
            *conp = fold (build1 (NEGATE_EXPR, TREE_TYPE (*conp), *conp));
            else
            return 0;
          }
        return 1;
      }
      if (TREE_CONSTANT (TREE_OPERAND (in, 0)))
      {
        *conp = TREE_OPERAND (in, 0);
        *varp = TREE_OPERAND (in, 1);
        if (TYPE_MODE (TREE_TYPE (*varp)) != TYPE_MODE (outtype)
            && TREE_TYPE (*varp) != outtype)
          *varp = convert (outtype, *varp);
        *varsignp = (TREE_CODE (in) == MINUS_EXPR) ? -1 : 1;
        return 1;
      }
    }
  return 0;
}

/* Combine two integer constants ARG1 and ARG2 under operation CODE
   to produce a new constant.

   If NOTRUNC is nonzero, do not truncate the result to fit the data type.
   If FORSIZE is nonzero, compute overflow for unsigned types.  */

static tree
int_const_binop (code, arg1, arg2, notrunc, forsize)
     enum tree_code code;
     register tree arg1, arg2;
     int notrunc, forsize;
{
  HOST_WIDE_INT int1l, int1h, int2l, int2h;
  HOST_WIDE_INT low, hi;
  HOST_WIDE_INT garbagel, garbageh;
  register tree t;
  int uns = TREE_UNSIGNED (TREE_TYPE (arg1));
  int overflow = 0;
  int no_overflow = 0;

  int1l = TREE_INT_CST_LOW (arg1);
  int1h = TREE_INT_CST_HIGH (arg1);
  int2l = TREE_INT_CST_LOW (arg2);
  int2h = TREE_INT_CST_HIGH (arg2);

  switch (code)
    {
    case BIT_IOR_EXPR:
      low = int1l | int2l, hi = int1h | int2h;
      break;

    case BIT_XOR_EXPR:
      low = int1l ^ int2l, hi = int1h ^ int2h;
      break;

    case BIT_AND_EXPR:
      low = int1l & int2l, hi = int1h & int2h;
      break;

    case BIT_ANDTC_EXPR:
      low = int1l & ~int2l, hi = int1h & ~int2h;
      break;

    case RSHIFT_EXPR:
      int2l = - int2l;
    case LSHIFT_EXPR:
      /* It's unclear from the C standard whether shifts can overflow.
       The following code ignores overflow; perhaps a C standard
       interpretation ruling is needed.  */
      lshift_double (int1l, int1h, int2l,
                 TYPE_PRECISION (TREE_TYPE (arg1)),
                 &low, &hi,
                 !uns);
      no_overflow = 1;
      break;

    case RROTATE_EXPR:
      int2l = - int2l;
    case LROTATE_EXPR:
      lrotate_double (int1l, int1h, int2l,
                  TYPE_PRECISION (TREE_TYPE (arg1)),
                  &low, &hi);
      break;

    case PLUS_EXPR:
      overflow = add_double (int1l, int1h, int2l, int2h, &low, &hi);
      break;

    case MINUS_EXPR:
      neg_double (int2l, int2h, &low, &hi);
      add_double (int1l, int1h, low, hi, &low, &hi);
      overflow = overflow_sum_sign (hi, int2h, int1h);
      break;

    case MULT_EXPR:
      overflow = mul_double (int1l, int1h, int2l, int2h, &low, &hi);
      break;

    case TRUNC_DIV_EXPR:
    case FLOOR_DIV_EXPR: case CEIL_DIV_EXPR:
    case EXACT_DIV_EXPR:
      /* This is a shortcut for a common special case.  */
      if (int2h == 0 && int2l > 0
        && ! TREE_CONSTANT_OVERFLOW (arg1)
        && ! TREE_CONSTANT_OVERFLOW (arg2)
        && int1h == 0 && int1l >= 0)
      {
        if (code == CEIL_DIV_EXPR)
          int1l += int2l - 1;
        low = int1l / int2l, hi = 0;
        break;
      }

      /* ... fall through ... */

    case ROUND_DIV_EXPR: 
      if (int2h == 0 && int2l == 1)
      {
        low = int1l, hi = int1h;
        break;
      }
      if (int1l == int2l && int1h == int2h
        && ! (int1l == 0 && int1h == 0))
      {
        low = 1, hi = 0;
        break;
      }
      overflow = div_and_round_double (code, uns,
                               int1l, int1h, int2l, int2h,
                               &low, &hi, &garbagel, &garbageh);
      break;

    case TRUNC_MOD_EXPR:
    case FLOOR_MOD_EXPR: case CEIL_MOD_EXPR:
      /* This is a shortcut for a common special case.  */
      if (int2h == 0 && int2l > 0
        && ! TREE_CONSTANT_OVERFLOW (arg1)
        && ! TREE_CONSTANT_OVERFLOW (arg2)
        && int1h == 0 && int1l >= 0)
      {
        if (code == CEIL_MOD_EXPR)
          int1l += int2l - 1;
        low = int1l % int2l, hi = 0;
        break;
      }

      /* ... fall through ... */

    case ROUND_MOD_EXPR: 
      overflow = div_and_round_double (code, uns,
                               int1l, int1h, int2l, int2h,
                               &garbagel, &garbageh, &low, &hi);
      break;

    case MIN_EXPR:
    case MAX_EXPR:
      if (uns)
      {
        low = (((unsigned HOST_WIDE_INT) int1h
              < (unsigned HOST_WIDE_INT) int2h)
             || (((unsigned HOST_WIDE_INT) int1h
                  == (unsigned HOST_WIDE_INT) int2h)
                 && ((unsigned HOST_WIDE_INT) int1l
                   < (unsigned HOST_WIDE_INT) int2l)));
      }
      else
      {
        low = ((int1h < int2h)
             || ((int1h == int2h)
                 && ((unsigned HOST_WIDE_INT) int1l
                   < (unsigned HOST_WIDE_INT) int2l)));
      }
      if (low == (code == MIN_EXPR))
      low = int1l, hi = int1h;
      else
      low = int2l, hi = int2h;
      break;

    default:
      abort ();
    }

  if (TREE_TYPE (arg1) == sizetype && hi == 0
      && low >= 0
      && (TYPE_MAX_VALUE (sizetype) == NULL
        || low <= TREE_INT_CST_LOW (TYPE_MAX_VALUE (sizetype)))
      && ! overflow
      && ! TREE_OVERFLOW (arg1) && ! TREE_OVERFLOW (arg2))
    t = size_int (low);
  else
    {
      t = build_int_2 (low, hi);
      TREE_TYPE (t) = TREE_TYPE (arg1);
    }

  TREE_OVERFLOW (t)
    = ((notrunc ? (!uns || forsize) && overflow
      : force_fit_type (t, (!uns || forsize) && overflow) && ! no_overflow)
       | TREE_OVERFLOW (arg1)
       | TREE_OVERFLOW (arg2));
  /* If we're doing a size calculation, unsigned arithmetic does overflow.
     So check if force_fit_type truncated the value.  */
  if (forsize
      && ! TREE_OVERFLOW (t)
      && (TREE_INT_CST_HIGH (t) != hi
        || TREE_INT_CST_LOW (t) != low))
    TREE_OVERFLOW (t) = 1;
  TREE_CONSTANT_OVERFLOW (t) = (TREE_OVERFLOW (t)
                        | TREE_CONSTANT_OVERFLOW (arg1)
                        | TREE_CONSTANT_OVERFLOW (arg2));
  return t;
}

/* Combine two constants ARG1 and ARG2 under operation CODE
   to produce a new constant.
   We assume ARG1 and ARG2 have the same data type,
   or at least are the same kind of constant and the same machine mode.

   If NOTRUNC is nonzero, do not truncate the result to fit the data type.  */

static tree
const_binop (code, arg1, arg2, notrunc)
     enum tree_code code;
     register tree arg1, arg2;
     int notrunc;
{
  STRIP_NOPS (arg1); STRIP_NOPS (arg2);

  if (TREE_CODE (arg1) == INTEGER_CST)
    return int_const_binop (code, arg1, arg2, notrunc, 0);

#if ! defined (REAL_IS_NOT_DOUBLE) || defined (REAL_ARITHMETIC)
  if (TREE_CODE (arg1) == REAL_CST)
    {
      REAL_VALUE_TYPE d1;
      REAL_VALUE_TYPE d2;
      int overflow = 0;
      REAL_VALUE_TYPE value;
      tree t;

      d1 = TREE_REAL_CST (arg1);
      d2 = TREE_REAL_CST (arg2);

      /* If either operand is a NaN, just return it.  Otherwise, set up
       for floating-point trap; we return an overflow.  */
      if (REAL_VALUE_ISNAN (d1))
      return arg1;
      else if (REAL_VALUE_ISNAN (d2))
      return arg2;
      else if (setjmp (float_error))
      {
        t = copy_node (arg1);
        overflow = 1;
        goto got_float;
      }

      set_float_handler (float_error);

#ifdef REAL_ARITHMETIC
      REAL_ARITHMETIC (value, code, d1, d2);
#else
      switch (code)
      {
      case PLUS_EXPR:
        value = d1 + d2;
        break;

      case MINUS_EXPR:
        value = d1 - d2;
        break;

      case MULT_EXPR:
        value = d1 * d2;
        break;

      case RDIV_EXPR:
#ifndef REAL_INFINITY
        if (d2 == 0)
          abort ();
#endif

        value = d1 / d2;
        break;

      case MIN_EXPR:
        value = MIN (d1, d2);
        break;

      case MAX_EXPR:
        value = MAX (d1, d2);
        break;

      default:
        abort ();
      }
#endif /* no REAL_ARITHMETIC */
      t = build_real (TREE_TYPE (arg1),
                  real_value_truncate (TYPE_MODE (TREE_TYPE (arg1)), value));
    got_float:
      set_float_handler (NULL_PTR);

      TREE_OVERFLOW (t)
      = (force_fit_type (t, overflow)
         | TREE_OVERFLOW (arg1) | TREE_OVERFLOW (arg2));
      TREE_CONSTANT_OVERFLOW (t)
      = TREE_OVERFLOW (t)
        | TREE_CONSTANT_OVERFLOW (arg1)
        | TREE_CONSTANT_OVERFLOW (arg2);
      return t;
    }
#endif /* not REAL_IS_NOT_DOUBLE, or REAL_ARITHMETIC */
  if (TREE_CODE (arg1) == COMPLEX_CST)
    {
      register tree type = TREE_TYPE (arg1);
      register tree r1 = TREE_REALPART (arg1);
      register tree i1 = TREE_IMAGPART (arg1);
      register tree r2 = TREE_REALPART (arg2);
      register tree i2 = TREE_IMAGPART (arg2);
      register tree t;

      switch (code)
      {
      case PLUS_EXPR:
        t = build_complex (type,
                       const_binop (PLUS_EXPR, r1, r2, notrunc),
                       const_binop (PLUS_EXPR, i1, i2, notrunc));
        break;

      case MINUS_EXPR:
        t = build_complex (type,
                       const_binop (MINUS_EXPR, r1, r2, notrunc),
                       const_binop (MINUS_EXPR, i1, i2, notrunc));
        break;

      case MULT_EXPR:
        t = build_complex (type,
                       const_binop (MINUS_EXPR,
                                const_binop (MULT_EXPR,
                                           r1, r2, notrunc),
                                const_binop (MULT_EXPR,
                                           i1, i2, notrunc),
                                notrunc),
                       const_binop (PLUS_EXPR,
                                const_binop (MULT_EXPR,
                                           r1, i2, notrunc),
                                const_binop (MULT_EXPR,
                                           i1, r2, notrunc),
                                notrunc));
        break;

      case RDIV_EXPR:
        {
          register tree magsquared
            = const_binop (PLUS_EXPR,
                       const_binop (MULT_EXPR, r2, r2, notrunc),
                       const_binop (MULT_EXPR, i2, i2, notrunc),
                       notrunc);

          t = build_complex (type,
                         const_binop
                         (INTEGRAL_TYPE_P (TREE_TYPE (r1))
                        ? TRUNC_DIV_EXPR : RDIV_EXPR,
                        const_binop (PLUS_EXPR,
                                   const_binop (MULT_EXPR, r1, r2,
                                            notrunc),
                                   const_binop (MULT_EXPR, i1, i2,
                                            notrunc),
                                   notrunc),
                        magsquared, notrunc),
                         const_binop
                         (INTEGRAL_TYPE_P (TREE_TYPE (r1))
                        ? TRUNC_DIV_EXPR : RDIV_EXPR,
                        const_binop (MINUS_EXPR,
                                   const_binop (MULT_EXPR, i1, r2,
                                            notrunc),
                                   const_binop (MULT_EXPR, r1, i2,
                                            notrunc),
                                   notrunc),
                        magsquared, notrunc));
        }
        break;

      default:
        abort ();
      }
      return t;
    }
  return 0;
}

/* Return an INTEGER_CST with value V .  The type is determined by bit_p:
   if it is zero, the type is taken from sizetype; if it is one, the type
   is taken from bitsizetype.  */

tree
size_int_wide (number, high, bit_p)
     unsigned HOST_WIDE_INT number, high;
     int bit_p;
{
  register tree t;
  /* Type-size nodes already made for small sizes.  */
  static tree size_table[2*HOST_BITS_PER_WIDE_INT + 1][2];

  if (number < 2*HOST_BITS_PER_WIDE_INT + 1 && ! high
      && size_table[number][bit_p] != 0)
    return size_table[number][bit_p];
  if (number < 2*HOST_BITS_PER_WIDE_INT + 1 && ! high)
    {
      push_obstacks_nochange ();
      /* Make this a permanent node.  */
      end_temporary_allocation ();
      t = build_int_2 (number, 0);
      TREE_TYPE (t) = bit_p ? bitsizetype : sizetype;
      size_table[number][bit_p] = t;
      pop_obstacks ();
    }
  else
    {
      t = build_int_2 (number, high);
      TREE_TYPE (t) = bit_p ? bitsizetype : sizetype;
      TREE_OVERFLOW (t) = TREE_CONSTANT_OVERFLOW (t) = force_fit_type (t, 0);
    }
  return t;
}

/* Combine operands OP1 and OP2 with arithmetic operation CODE.
   CODE is a tree code.  Data type is taken from `sizetype',
   If the operands are constant, so is the result.  */

tree
size_binop (code, arg0, arg1)
     enum tree_code code;
     tree arg0, arg1;
{
  /* Handle the special case of two integer constants faster.  */
  if (TREE_CODE (arg0) == INTEGER_CST && TREE_CODE (arg1) == INTEGER_CST)
    {
      /* And some specific cases even faster than that.  */
      if (code == PLUS_EXPR && integer_zerop (arg0))
      return arg1;
      else if ((code == MINUS_EXPR || code == PLUS_EXPR)
             && integer_zerop (arg1))
      return arg0;
      else if (code == MULT_EXPR && integer_onep (arg0))
      return arg1;

      /* Handle general case of two integer constants.  */
      return int_const_binop (code, arg0, arg1, 0, 1);
    }

  if (arg0 == error_mark_node || arg1 == error_mark_node)
    return error_mark_node;

  return fold (build (code, sizetype, arg0, arg1));
}

/* Combine operands OP1 and OP2 with arithmetic operation CODE.
   CODE is a tree code.  Data type is taken from `ssizetype',
   If the operands are constant, so is the result.  */

tree
ssize_binop (code, arg0, arg1)
     enum tree_code code;
     tree arg0, arg1;
{
  /* Handle the special case of two integer constants faster.  */
  if (TREE_CODE (arg0) == INTEGER_CST && TREE_CODE (arg1) == INTEGER_CST)
    {
      /* And some specific cases even faster than that.  */
      if (code == PLUS_EXPR && integer_zerop (arg0))
      return arg1;
      else if ((code == MINUS_EXPR || code == PLUS_EXPR)
             && integer_zerop (arg1))
      return arg0;
      else if (code == MULT_EXPR && integer_onep (arg0))
      return arg1;

      /* Handle general case of two integer constants.  We convert
         arg0 to ssizetype because int_const_binop uses its type for the
       return value.  */
      arg0 = convert (ssizetype, arg0);
      return int_const_binop (code, arg0, arg1, 0, 0);
    }

  if (arg0 == error_mark_node || arg1 == error_mark_node)
    return error_mark_node;

  return fold (build (code, ssizetype, arg0, arg1));
}

/* Given T, a tree representing type conversion of ARG1, a constant,
   return a constant tree representing the result of conversion.  */

static tree
fold_convert (t, arg1)
     register tree t;
     register tree arg1;
{
  register tree type = TREE_TYPE (t);
  int overflow = 0;

  if (POINTER_TYPE_P (type) || INTEGRAL_TYPE_P (type))
    {
      if (TREE_CODE (arg1) == INTEGER_CST)
      {
        /* If we would build a constant wider than GCC supports,
           leave the conversion unfolded.  */
        if (TYPE_PRECISION (type) > 2 * HOST_BITS_PER_WIDE_INT)
          return t;

        /* Given an integer constant, make new constant with new type,
           appropriately sign-extended or truncated.  */
        t = build_int_2 (TREE_INT_CST_LOW (arg1),
                     TREE_INT_CST_HIGH (arg1));
        TREE_TYPE (t) = type;
        /* Indicate an overflow if (1) ARG1 already overflowed,
           or (2) force_fit_type indicates an overflow.
           Tell force_fit_type that an overflow has already occurred
           if ARG1 is a too-large unsigned value and T is signed.
           But don't indicate an overflow if converting a pointer.  */
        TREE_OVERFLOW (t)
          = ((force_fit_type (t,
                        (TREE_INT_CST_HIGH (arg1) < 0
                         && (TREE_UNSIGNED (type)
                            < TREE_UNSIGNED (TREE_TYPE (arg1)))))
            && ! POINTER_TYPE_P (TREE_TYPE (arg1)))
             || TREE_OVERFLOW (arg1));
        TREE_CONSTANT_OVERFLOW (t)
          = TREE_OVERFLOW (t) | TREE_CONSTANT_OVERFLOW (arg1);
      }
#if !defined (REAL_IS_NOT_DOUBLE) || defined (REAL_ARITHMETIC)
      else if (TREE_CODE (arg1) == REAL_CST)
      {
        /* Don't initialize these, use assignments.
           Initialized local aggregates don't work on old compilers.  */
        REAL_VALUE_TYPE x;
        REAL_VALUE_TYPE l;
        REAL_VALUE_TYPE u;
        tree type1 = TREE_TYPE (arg1);
        int no_upper_bound;

        x = TREE_REAL_CST (arg1);
        l = real_value_from_int_cst (type1, TYPE_MIN_VALUE (type));

        no_upper_bound = (TYPE_MAX_VALUE (type) == NULL);
        if (!no_upper_bound)
          u = real_value_from_int_cst (type1, TYPE_MAX_VALUE (type));

        /* See if X will be in range after truncation towards 0.
           To compensate for truncation, move the bounds away from 0,
           but reject if X exactly equals the adjusted bounds.  */
#ifdef REAL_ARITHMETIC
        REAL_ARITHMETIC (l, MINUS_EXPR, l, dconst1);
        if (!no_upper_bound)
          REAL_ARITHMETIC (u, PLUS_EXPR, u, dconst1);
#else
        l--;
        if (!no_upper_bound)
          u++;
#endif
        /* If X is a NaN, use zero instead and show we have an overflow.
           Otherwise, range check.  */
        if (REAL_VALUE_ISNAN (x))
          overflow = 1, x = dconst0;
        else if (! (REAL_VALUES_LESS (l, x)
                  && !no_upper_bound
                  && REAL_VALUES_LESS (x, u)))
          overflow = 1;

#ifndef REAL_ARITHMETIC
        {
          HOST_WIDE_INT low, high;
          HOST_WIDE_INT half_word
            = (HOST_WIDE_INT) 1 << (HOST_BITS_PER_WIDE_INT / 2);

          if (x < 0)
            x = -x;

          high = (HOST_WIDE_INT) (x / half_word / half_word);
          x -= (REAL_VALUE_TYPE) high * half_word * half_word;
          if (x >= (REAL_VALUE_TYPE) half_word * half_word / 2)
            {
            low = x - (REAL_VALUE_TYPE) half_word * half_word / 2;
            low |= (HOST_WIDE_INT) -1 << (HOST_BITS_PER_WIDE_INT - 1);
            }
          else
            low = (HOST_WIDE_INT) x;
          if (TREE_REAL_CST (arg1) < 0)
            neg_double (low, high, &low, &high);
          t = build_int_2 (low, high);
        }
#else
        {
          HOST_WIDE_INT low, high;
          REAL_VALUE_TO_INT (&low, &high, x);
          t = build_int_2 (low, high);
        }
#endif
        TREE_TYPE (t) = type;
        TREE_OVERFLOW (t)
          = TREE_OVERFLOW (arg1) | force_fit_type (t, overflow);
        TREE_CONSTANT_OVERFLOW (t)
          = TREE_OVERFLOW (t) | TREE_CONSTANT_OVERFLOW (arg1);
      }
#endif /* not REAL_IS_NOT_DOUBLE, or REAL_ARITHMETIC */
      TREE_TYPE (t) = type;
    }
  else if (TREE_CODE (type) == REAL_TYPE)
    {
#if !defined (REAL_IS_NOT_DOUBLE) || defined (REAL_ARITHMETIC)
      if (TREE_CODE (arg1) == INTEGER_CST)
      return build_real_from_int_cst (type, arg1);
#endif /* not REAL_IS_NOT_DOUBLE, or REAL_ARITHMETIC */
      if (TREE_CODE (arg1) == REAL_CST)
      {
        if (REAL_VALUE_ISNAN (TREE_REAL_CST (arg1)))
          {
            t = arg1;
            TREE_TYPE (arg1) = type;
            return t;
          }
        else if (setjmp (float_error))
          {
            overflow = 1;
            t = copy_node (arg1);
            goto got_it;
          }
        set_float_handler (float_error);

        t = build_real (type, real_value_truncate (TYPE_MODE (type),
                                         TREE_REAL_CST (arg1)));
        set_float_handler (NULL_PTR);

      got_it:
        TREE_OVERFLOW (t)
          = TREE_OVERFLOW (arg1) | force_fit_type (t, overflow);
        TREE_CONSTANT_OVERFLOW (t)
          = TREE_OVERFLOW (t) | TREE_CONSTANT_OVERFLOW (arg1);
        return t;
      }
    }
  TREE_CONSTANT (t) = 1;
  return t;
}

/* Return an expr equal to X but certainly not valid as an lvalue.
   Also make sure it is not valid as an null pointer constant.  */

tree
non_lvalue (x)
     tree x;
{
  tree result;

  /* These things are certainly not lvalues.  */
  if (TREE_CODE (x) == NON_LVALUE_EXPR
      || TREE_CODE (x) == INTEGER_CST
      || TREE_CODE (x) == REAL_CST
      || TREE_CODE (x) == STRING_CST
      || TREE_CODE (x) == ADDR_EXPR)
    {
      if (TREE_CODE (x) == INTEGER_CST && integer_zerop (x))
      {
        /* Use NOP_EXPR instead of NON_LVALUE_EXPR
           so convert_for_assignment won't strip it.
           This is so this 0 won't be treated as a null pointer constant.  */
        result = build1 (NOP_EXPR, TREE_TYPE (x), x);
        TREE_CONSTANT (result) = TREE_CONSTANT (x);
        return result;
      }
      return x;
    }

  result = build1 (NON_LVALUE_EXPR, TREE_TYPE (x), x);
  TREE_CONSTANT (result) = TREE_CONSTANT (x);
  return result;
}

/* Nonzero means lvalues are limited to those valid in pedantic ANSI C.
   Zero means allow extended lvalues.  */

int pedantic_lvalues;

/* When pedantic, return an expr equal to X but certainly not valid as a
   pedantic lvalue.  Otherwise, return X.  */

tree
pedantic_non_lvalue (x)
     tree x;
{
  if (pedantic_lvalues)
    return non_lvalue (x);
  else
    return x;
}

/* Given a tree comparison code, return the code that is the logical inverse
   of the given code.  It is not safe to do this for floating-point
   comparisons, except for NE_EXPR and EQ_EXPR.  */

static enum tree_code
invert_tree_comparison (code)
     enum tree_code code;
{
  switch (code)
    {
    case EQ_EXPR:
      return NE_EXPR;
    case NE_EXPR:
      return EQ_EXPR;
    case GT_EXPR:
      return LE_EXPR;
    case GE_EXPR:
      return LT_EXPR;
    case LT_EXPR:
      return GE_EXPR;
    case LE_EXPR:
      return GT_EXPR;
    default:
      abort ();
    }
}

/* Similar, but return the comparison that results if the operands are
   swapped.  This is safe for floating-point.  */

static enum tree_code
swap_tree_comparison (code)
     enum tree_code code;
{
  switch (code)
    {
    case EQ_EXPR:
    case NE_EXPR:
      return code;
    case GT_EXPR:
      return LT_EXPR;
    case GE_EXPR:
      return LE_EXPR;
    case LT_EXPR:
      return GT_EXPR;
    case LE_EXPR:
      return GE_EXPR;
    default:
      abort ();
    }
}

/* Return nonzero if CODE is a tree code that represents a truth value.  */

static int
truth_value_p (code)
     enum tree_code code;
{
  return (TREE_CODE_CLASS (code) == '<'
        || code == TRUTH_AND_EXPR || code == TRUTH_ANDIF_EXPR
        || code == TRUTH_OR_EXPR || code == TRUTH_ORIF_EXPR
        || code == TRUTH_XOR_EXPR || code == TRUTH_NOT_EXPR);
}

/* Return nonzero if two operands are necessarily equal.
   If ONLY_CONST is non-zero, only return non-zero for constants.
   This function tests whether the operands are indistinguishable;
   it does not test whether they are equal using C's == operation.
   The distinction is important for IEEE floating point, because
   (1) -0.0 and 0.0 are distinguishable, but -0.0==0.0, and
   (2) two NaNs may be indistinguishable, but NaN!=NaN.  */

int
operand_equal_p (arg0, arg1, only_const)
     tree arg0, arg1;
     int only_const;
{
  /* If both types don't have the same signedness, then we can't consider
     them equal.  We must check this before the STRIP_NOPS calls
     because they may change the signedness of the arguments.  */
  if (TREE_UNSIGNED (TREE_TYPE (arg0)) != TREE_UNSIGNED (TREE_TYPE (arg1)))
    return 0;

  STRIP_NOPS (arg0);
  STRIP_NOPS (arg1);

  if (TREE_CODE (arg0) != TREE_CODE (arg1)
      /* This is needed for conversions and for COMPONENT_REF.
       Might as well play it safe and always test this.  */
      || TYPE_MODE (TREE_TYPE (arg0)) != TYPE_MODE (TREE_TYPE (arg1)))
    return 0;

  /* If ARG0 and ARG1 are the same SAVE_EXPR, they are necessarily equal.
     We don't care about side effects in that case because the SAVE_EXPR
     takes care of that for us. In all other cases, two expressions are
     equal if they have no side effects.  If we have two identical
     expressions with side effects that should be treated the same due
     to the only side effects being identical SAVE_EXPR's, that will
     be detected in the recursive calls below.  */
  if (arg0 == arg1 && ! only_const
      && (TREE_CODE (arg0) == SAVE_EXPR
        || (! TREE_SIDE_EFFECTS (arg0) && ! TREE_SIDE_EFFECTS (arg1))))
    return 1;

  /* Next handle constant cases, those for which we can return 1 even
     if ONLY_CONST is set.  */
  if (TREE_CONSTANT (arg0) && TREE_CONSTANT (arg1))
    switch (TREE_CODE (arg0))
      {
      case INTEGER_CST:
      return (! TREE_CONSTANT_OVERFLOW (arg0)
            && ! TREE_CONSTANT_OVERFLOW (arg1)
            && TREE_INT_CST_LOW (arg0) == TREE_INT_CST_LOW (arg1)
            && TREE_INT_CST_HIGH (arg0) == TREE_INT_CST_HIGH (arg1));

      case REAL_CST:
      return (! TREE_CONSTANT_OVERFLOW (arg0)
            && ! TREE_CONSTANT_OVERFLOW (arg1)
            && REAL_VALUES_IDENTICAL (TREE_REAL_CST (arg0),
                                TREE_REAL_CST (arg1)));

      case COMPLEX_CST:
      return (operand_equal_p (TREE_REALPART (arg0), TREE_REALPART (arg1),
                         only_const)
            && operand_equal_p (TREE_IMAGPART (arg0), TREE_IMAGPART (arg1),
                            only_const));

      case STRING_CST:
      return (TREE_STRING_LENGTH (arg0) == TREE_STRING_LENGTH (arg1)
            && ! strncmp (TREE_STRING_POINTER (arg0),
                        TREE_STRING_POINTER (arg1),
                        TREE_STRING_LENGTH (arg0)));

      case ADDR_EXPR:
      return operand_equal_p (TREE_OPERAND (arg0, 0), TREE_OPERAND (arg1, 0),
                        0);
      default:
      break;
      }

  if (only_const)
    return 0;

  switch (TREE_CODE_CLASS (TREE_CODE (arg0)))
    {
    case '1':
      /* Two conversions are equal only if signedness and modes match.  */
      if ((TREE_CODE (arg0) == NOP_EXPR || TREE_CODE (arg0) == CONVERT_EXPR)
        && (TREE_UNSIGNED (TREE_TYPE (arg0))
            != TREE_UNSIGNED (TREE_TYPE (arg1))))
      return 0;

      return operand_equal_p (TREE_OPERAND (arg0, 0),
                        TREE_OPERAND (arg1, 0), 0);

    case '<':
    case '2':
      if (operand_equal_p (TREE_OPERAND (arg0, 0), TREE_OPERAND (arg1, 0), 0)
        && operand_equal_p (TREE_OPERAND (arg0, 1), TREE_OPERAND (arg1, 1),
                        0))
      return 1;

      /* For commutative ops, allow the other order.  */
      return ((TREE_CODE (arg0) == PLUS_EXPR || TREE_CODE (arg0) == MULT_EXPR
             || TREE_CODE (arg0) == MIN_EXPR || TREE_CODE (arg0) == MAX_EXPR
             || TREE_CODE (arg0) == BIT_IOR_EXPR
             || TREE_CODE (arg0) == BIT_XOR_EXPR
             || TREE_CODE (arg0) == BIT_AND_EXPR
             || TREE_CODE (arg0) == NE_EXPR || TREE_CODE (arg0) == EQ_EXPR)
            && operand_equal_p (TREE_OPERAND (arg0, 0),
                          TREE_OPERAND (arg1, 1), 0)
            && operand_equal_p (TREE_OPERAND (arg0, 1),
                          TREE_OPERAND (arg1, 0), 0));

    case 'r':
      switch (TREE_CODE (arg0))
      {
      case INDIRECT_REF:
        return operand_equal_p (TREE_OPERAND (arg0, 0),
                          TREE_OPERAND (arg1, 0), 0);

      case COMPONENT_REF:
      case ARRAY_REF:
        return (operand_equal_p (TREE_OPERAND (arg0, 0),
                           TREE_OPERAND (arg1, 0), 0)
              && operand_equal_p (TREE_OPERAND (arg0, 1),
                              TREE_OPERAND (arg1, 1), 0));

      case BIT_FIELD_REF:
        return (operand_equal_p (TREE_OPERAND (arg0, 0),
                           TREE_OPERAND (arg1, 0), 0)
              && operand_equal_p (TREE_OPERAND (arg0, 1),
                              TREE_OPERAND (arg1, 1), 0)
              && operand_equal_p (TREE_OPERAND (arg0, 2),
                              TREE_OPERAND (arg1, 2), 0));
      default:
        return 0;
      }
      
    default:
      return 0;
    }
}

/* Similar to operand_equal_p, but see if ARG0 might have been made by
   shorten_compare from ARG1 when ARG1 was being compared with OTHER. 

   When in doubt, return 0.  */

static int 
operand_equal_for_comparison_p (arg0, arg1, other)
     tree arg0, arg1;
     tree other;
{
  int unsignedp1, unsignedpo;
  tree primarg0, primarg1, primother;
  unsigned correct_width;

  if (operand_equal_p (arg0, arg1, 0))
    return 1;

  if (! INTEGRAL_TYPE_P (TREE_TYPE (arg0))
      || ! INTEGRAL_TYPE_P (TREE_TYPE (arg1)))
    return 0;

  /* Discard any conversions that don't change the modes of ARG0 and ARG1
     and see if the inner values are the same.  This removes any
     signedness comparison, which doesn't matter here.  */
  primarg0 = arg0, primarg1 = arg1;
  STRIP_NOPS (primarg0);  STRIP_NOPS (primarg1);
  if (operand_equal_p (primarg0, primarg1, 0))
    return 1;

  /* Duplicate what shorten_compare does to ARG1 and see if that gives the
     actual comparison operand, ARG0.

     First throw away any conversions to wider types
     already present in the operands.  */

  primarg1 = get_narrower (arg1, &unsignedp1);
  primother = get_narrower (other, &unsignedpo);

  correct_width = TYPE_PRECISION (TREE_TYPE (arg1));
  if (unsignedp1 == unsignedpo
      && TYPE_PRECISION (TREE_TYPE (primarg1)) < correct_width
      && TYPE_PRECISION (TREE_TYPE (primother)) < correct_width)
    {
      tree type = TREE_TYPE (arg0);

      /* Make sure shorter operand is extended the right way
       to match the longer operand.  */
      primarg1 = convert (signed_or_unsigned_type (unsignedp1,
                                      TREE_TYPE (primarg1)),
                   primarg1);

      if (operand_equal_p (arg0, convert (type, primarg1), 0))
      return 1;
    }

  return 0;
}

/* See if ARG is an expression that is either a comparison or is performing
   arithmetic on comparisons.  The comparisons must only be comparing
   two different values, which will be stored in *CVAL1 and *CVAL2; if
   they are non-zero it means that some operands have already been found.
   No variables may be used anywhere else in the expression except in the
   comparisons.  If SAVE_P is true it means we removed a SAVE_EXPR around
   the expression and save_expr needs to be called with CVAL1 and CVAL2.

   If this is true, return 1.  Otherwise, return zero.  */

static int
twoval_comparison_p (arg, cval1, cval2, save_p)
     tree arg;
     tree *cval1, *cval2;
     int *save_p;
{
  enum tree_code code = TREE_CODE (arg);
  char class = TREE_CODE_CLASS (code);

  /* We can handle some of the 'e' cases here.  */
  if (class == 'e' && code == TRUTH_NOT_EXPR)
    class = '1';
  else if (class == 'e'
         && (code == TRUTH_ANDIF_EXPR || code == TRUTH_ORIF_EXPR
             || code == COMPOUND_EXPR))
    class = '2';

  /* ??? Disable this since the SAVE_EXPR might already be in use outside
     the expression.  There may be no way to make this work, but it needs
     to be looked at again for 2.6.  */
#if 0
  else if (class == 'e' && code == SAVE_EXPR && SAVE_EXPR_RTL (arg) == 0)
    {
      /* If we've already found a CVAL1 or CVAL2, this expression is
       two complex to handle.  */
      if (*cval1 || *cval2)
      return 0;

      class = '1';
      *save_p = 1;
    }
#endif

  switch (class)
    {
    case '1':
      return twoval_comparison_p (TREE_OPERAND (arg, 0), cval1, cval2, save_p);

    case '2':
      return (twoval_comparison_p (TREE_OPERAND (arg, 0), cval1, cval2, save_p)
            && twoval_comparison_p (TREE_OPERAND (arg, 1),
                              cval1, cval2, save_p));

    case 'c':
      return 1;

    case 'e':
      if (code == COND_EXPR)
      return (twoval_comparison_p (TREE_OPERAND (arg, 0),
                             cval1, cval2, save_p)
            && twoval_comparison_p (TREE_OPERAND (arg, 1),
                              cval1, cval2, save_p)
            && twoval_comparison_p (TREE_OPERAND (arg, 2),
                              cval1, cval2, save_p));
      return 0;
        
    case '<':
      /* First see if we can handle the first operand, then the second.  For
       the second operand, we know *CVAL1 can't be zero.  It must be that
       one side of the comparison is each of the values; test for the
       case where this isn't true by failing if the two operands
       are the same.  */

      if (operand_equal_p (TREE_OPERAND (arg, 0),
                     TREE_OPERAND (arg, 1), 0))
      return 0;

      if (*cval1 == 0)
      *cval1 = TREE_OPERAND (arg, 0);
      else if (operand_equal_p (*cval1, TREE_OPERAND (arg, 0), 0))
      ;
      else if (*cval2 == 0)
      *cval2 = TREE_OPERAND (arg, 0);
      else if (operand_equal_p (*cval2, TREE_OPERAND (arg, 0), 0))
      ;
      else
      return 0;

      if (operand_equal_p (*cval1, TREE_OPERAND (arg, 1), 0))
      ;
      else if (*cval2 == 0)
      *cval2 = TREE_OPERAND (arg, 1);
      else if (operand_equal_p (*cval2, TREE_OPERAND (arg, 1), 0))
      ;
      else
      return 0;

      return 1;

    default:
      return 0;
    }
}

/* ARG is a tree that is known to contain just arithmetic operations and
   comparisons.  Evaluate the operations in the tree substituting NEW0 for
   any occurrence of OLD0 as an operand of a comparison and likewise for
   NEW1 and OLD1.  */

static tree
eval_subst (arg, old0, new0, old1, new1)
     tree arg;
     tree old0, new0, old1, new1;
{
  tree type = TREE_TYPE (arg);
  enum tree_code code = TREE_CODE (arg);
  char class = TREE_CODE_CLASS (code);

  /* We can handle some of the 'e' cases here.  */
  if (class == 'e' && code == TRUTH_NOT_EXPR)
    class = '1';
  else if (class == 'e'
         && (code == TRUTH_ANDIF_EXPR || code == TRUTH_ORIF_EXPR))
    class = '2';

  switch (class)
    {
    case '1':
      return fold (build1 (code, type,
                     eval_subst (TREE_OPERAND (arg, 0),
                               old0, new0, old1, new1)));

    case '2':
      return fold (build (code, type,
                    eval_subst (TREE_OPERAND (arg, 0),
                              old0, new0, old1, new1),
                    eval_subst (TREE_OPERAND (arg, 1),
                              old0, new0, old1, new1)));

    case 'e':
      switch (code)
      {
      case SAVE_EXPR:
        return eval_subst (TREE_OPERAND (arg, 0), old0, new0, old1, new1);

      case COMPOUND_EXPR:
        return eval_subst (TREE_OPERAND (arg, 1), old0, new0, old1, new1);

      case COND_EXPR:
        return fold (build (code, type,
                        eval_subst (TREE_OPERAND (arg, 0),
                                old0, new0, old1, new1),
                        eval_subst (TREE_OPERAND (arg, 1),
                                old0, new0, old1, new1),
                        eval_subst (TREE_OPERAND (arg, 2),
                                old0, new0, old1, new1)));
      default:
        break;
      }
      /* fall through (???) */

    case '<':
      {
      tree arg0 = TREE_OPERAND (arg, 0);
      tree arg1 = TREE_OPERAND (arg, 1);

      /* We need to check both for exact equality and tree equality.  The
         former will be true if the operand has a side-effect.  In that
         case, we know the operand occurred exactly once.  */

      if (arg0 == old0 || operand_equal_p (arg0, old0, 0))
        arg0 = new0;
      else if (arg0 == old1 || operand_equal_p (arg0, old1, 0))
        arg0 = new1;

      if (arg1 == old0 || operand_equal_p (arg1, old0, 0))
        arg1 = new0;
      else if (arg1 == old1 || operand_equal_p (arg1, old1, 0))
        arg1 = new1;

      return fold (build (code, type, arg0, arg1));
      }

    default:
      return arg;
    }
}

/* Return a tree for the case when the result of an expression is RESULT
   converted to TYPE and OMITTED was previously an operand of the expression
   but is now not needed (e.g., we folded OMITTED * 0).

   If OMITTED has side effects, we must evaluate it.  Otherwise, just do
   the conversion of RESULT to TYPE.  */

static tree
omit_one_operand (type, result, omitted)
     tree type, result, omitted;
{
  tree t = convert (type, result);

  if (TREE_SIDE_EFFECTS (omitted))
    return build (COMPOUND_EXPR, type, omitted, t);

  return non_lvalue (t);
}

/* Similar, but call pedantic_non_lvalue instead of non_lvalue.  */

static tree
pedantic_omit_one_operand (type, result, omitted)
     tree type, result, omitted;
{
  tree t = convert (type, result);

  if (TREE_SIDE_EFFECTS (omitted))
    return build (COMPOUND_EXPR, type, omitted, t);

  return pedantic_non_lvalue (t);
}



/* Return a simplified tree node for the truth-negation of ARG.  This
   never alters ARG itself.  We assume that ARG is an operation that
   returns a truth value (0 or 1).  */

tree
invert_truthvalue (arg)
     tree arg;
{
  tree type = TREE_TYPE (arg);
  enum tree_code code = TREE_CODE (arg);

  if (code == ERROR_MARK)
    return arg;

  /* If this is a comparison, we can simply invert it, except for
     floating-point non-equality comparisons, in which case we just
     enclose a TRUTH_NOT_EXPR around what we have.  */

  if (TREE_CODE_CLASS (code) == '<')
    {
      if (FLOAT_TYPE_P (TREE_TYPE (TREE_OPERAND (arg, 0)))
        && code != NE_EXPR && code != EQ_EXPR)
      return build1 (TRUTH_NOT_EXPR, type, arg);
      else
      return build (invert_tree_comparison (code), type,
                  TREE_OPERAND (arg, 0), TREE_OPERAND (arg, 1));
    }

  switch (code)
    {
    case INTEGER_CST:
      return convert (type, build_int_2 (TREE_INT_CST_LOW (arg) == 0
                               && TREE_INT_CST_HIGH (arg) == 0, 0));

    case TRUTH_AND_EXPR:
      return build (TRUTH_OR_EXPR, type,
                invert_truthvalue (TREE_OPERAND (arg, 0)),
                invert_truthvalue (TREE_OPERAND (arg, 1)));

    case TRUTH_OR_EXPR:
      return build (TRUTH_AND_EXPR, type,
                invert_truthvalue (TREE_OPERAND (arg, 0)),
                invert_truthvalue (TREE_OPERAND (arg, 1)));

    case TRUTH_XOR_EXPR:
      /* Here we can invert either operand.  We invert the first operand
       unless the second operand is a TRUTH_NOT_EXPR in which case our
       result is the XOR of the first operand with the inside of the
       negation of the second operand.  */

      if (TREE_CODE (TREE_OPERAND (arg, 1)) == TRUTH_NOT_EXPR)
      return build (TRUTH_XOR_EXPR, type, TREE_OPERAND (arg, 0),
                  TREE_OPERAND (TREE_OPERAND (arg, 1), 0));
      else
      return build (TRUTH_XOR_EXPR, type,
                  invert_truthvalue (TREE_OPERAND (arg, 0)),
                  TREE_OPERAND (arg, 1));

    case TRUTH_ANDIF_EXPR:
      return build (TRUTH_ORIF_EXPR, type,
                invert_truthvalue (TREE_OPERAND (arg, 0)),
                invert_truthvalue (TREE_OPERAND (arg, 1)));

    case TRUTH_ORIF_EXPR:
      return build (TRUTH_ANDIF_EXPR, type,
                invert_truthvalue (TREE_OPERAND (arg, 0)),
                invert_truthvalue (TREE_OPERAND (arg, 1)));

    case TRUTH_NOT_EXPR:
      return TREE_OPERAND (arg, 0);

    case COND_EXPR:
      return build (COND_EXPR, type, TREE_OPERAND (arg, 0),
                invert_truthvalue (TREE_OPERAND (arg, 1)),
                invert_truthvalue (TREE_OPERAND (arg, 2)));

    case COMPOUND_EXPR:
      return build (COMPOUND_EXPR, type, TREE_OPERAND (arg, 0),
                invert_truthvalue (TREE_OPERAND (arg, 1)));

    case NON_LVALUE_EXPR:
      return invert_truthvalue (TREE_OPERAND (arg, 0));

    case NOP_EXPR:
    case CONVERT_EXPR:
    case FLOAT_EXPR:
      return build1 (TREE_CODE (arg), type,
                 invert_truthvalue (TREE_OPERAND (arg, 0)));

    case BIT_AND_EXPR:
      if (!integer_onep (TREE_OPERAND (arg, 1)))
      break;
      return build (EQ_EXPR, type, arg, convert (type, integer_zero_node));

    case SAVE_EXPR:
      return build1 (TRUTH_NOT_EXPR, type, arg);

    case CLEANUP_POINT_EXPR:
      return build1 (CLEANUP_POINT_EXPR, type,
                 invert_truthvalue (TREE_OPERAND (arg, 0)));

    default:
      break;
    }
  if (TREE_CODE (TREE_TYPE (arg)) != BOOLEAN_TYPE)
    abort ();
  return build1 (TRUTH_NOT_EXPR, type, arg);
}

/* Given a bit-wise operation CODE applied to ARG0 and ARG1, see if both
   operands are another bit-wise operation with a common input.  If so,
   distribute the bit operations to save an operation and possibly two if
   constants are involved.  For example, convert
      (A | B) & (A | C) into A | (B & C)
   Further simplification will occur if B and C are constants.

   If this optimization cannot be done, 0 will be returned.  */

static tree
distribute_bit_expr (code, type, arg0, arg1)
     enum tree_code code;
     tree type;
     tree arg0, arg1;
{
  tree common;
  tree left, right;

  if (TREE_CODE (arg0) != TREE_CODE (arg1)
      || TREE_CODE (arg0) == code
      || (TREE_CODE (arg0) != BIT_AND_EXPR
        && TREE_CODE (arg0) != BIT_IOR_EXPR))
    return 0;

  if (operand_equal_p (TREE_OPERAND (arg0, 0), TREE_OPERAND (arg1, 0), 0))
    {
      common = TREE_OPERAND (arg0, 0);
      left = TREE_OPERAND (arg0, 1);
      right = TREE_OPERAND (arg1, 1);
    }
  else if (operand_equal_p (TREE_OPERAND (arg0, 0), TREE_OPERAND (arg1, 1), 0))
    {
      common = TREE_OPERAND (arg0, 0);
      left = TREE_OPERAND (arg0, 1);
      right = TREE_OPERAND (arg1, 0);
    }
  else if (operand_equal_p (TREE_OPERAND (arg0, 1), TREE_OPERAND (arg1, 0), 0))
    {
      common = TREE_OPERAND (arg0, 1);
      left = TREE_OPERAND (arg0, 0);
      right = TREE_OPERAND (arg1, 1);
    }
  else if (operand_equal_p (TREE_OPERAND (arg0, 1), TREE_OPERAND (arg1, 1), 0))
    {
      common = TREE_OPERAND (arg0, 1);
      left = TREE_OPERAND (arg0, 0);
      right = TREE_OPERAND (arg1, 0);
    }
  else
    return 0;

  return fold (build (TREE_CODE (arg0), type, common,
                  fold (build (code, type, left, right))));
}

/* Return a BIT_FIELD_REF of type TYPE to refer to BITSIZE bits of INNER
   starting at BITPOS.  The field is unsigned if UNSIGNEDP is non-zero.  */

static tree
make_bit_field_ref (inner, type, bitsize, bitpos, unsignedp)
     tree inner;
     tree type;
     int bitsize, bitpos;
     int unsignedp;
{
  tree result = build (BIT_FIELD_REF, type, inner,
                   size_int (bitsize), bitsize_int (bitpos, 0L));

  TREE_UNSIGNED (result) = unsignedp;

  return result;
}

/* Optimize a bit-field compare.

   There are two cases:  First is a compare against a constant and the
   second is a comparison of two items where the fields are at the same
   bit position relative to the start of a chunk (byte, halfword, word)
   large enough to contain it.  In these cases we can avoid the shift
   implicit in bitfield extractions.

   For constants, we emit a compare of the shifted constant with the
   BIT_AND_EXPR of a mask and a byte, halfword, or word of the operand being
   compared.  For two fields at the same position, we do the ANDs with the
   similar mask and compare the result of the ANDs.

   CODE is the comparison code, known to be either NE_EXPR or EQ_EXPR.
   COMPARE_TYPE is the type of the comparison, and LHS and RHS
   are the left and right operands of the comparison, respectively.

   If the optimization described above can be done, we return the resulting
   tree.  Otherwise we return zero.  */

static tree
optimize_bit_field_compare (code, compare_type, lhs, rhs)
     enum tree_code code;
     tree compare_type;
     tree lhs, rhs;
{
  int lbitpos, lbitsize, rbitpos, rbitsize;
  int lnbitpos, lnbitsize, rnbitpos = 0, rnbitsize = 0;
  tree type = TREE_TYPE (lhs);
  tree signed_type, unsigned_type;
  int const_p = TREE_CODE (rhs) == INTEGER_CST;
  enum machine_mode lmode, rmode, lnmode, rnmode = VOIDmode;
  int lunsignedp, runsignedp;
  int lvolatilep = 0, rvolatilep = 0;
  int alignment;
  tree linner, rinner = NULL_TREE;
  tree mask;
  tree offset;

  /* Get all the information about the extractions being done.  If the bit size
     if the same as the size of the underlying object, we aren't doing an
     extraction at all and so can do nothing.  */
  linner = get_inner_reference (lhs, &lbitsize, &lbitpos, &offset, &lmode,
                        &lunsignedp, &lvolatilep, &alignment);
  if (linner == lhs || lbitsize == GET_MODE_BITSIZE (lmode) || lbitsize < 0
      || offset != 0)
    return 0;

 if (!const_p)
   {
     /* If this is not a constant, we can only do something if bit positions,
      sizes, and signedness are the same.   */
     rinner = get_inner_reference (rhs, &rbitsize, &rbitpos, &offset, &rmode,
                           &runsignedp, &rvolatilep, &alignment);

     if (rinner == rhs || lbitpos != rbitpos || lbitsize != rbitsize
       || lunsignedp != runsignedp || offset != 0)
       return 0;
   }

  /* See if we can find a mode to refer to this field.  We should be able to,
     but fail if we can't.  */
  lnmode = get_best_mode (lbitsize, lbitpos,
                    TYPE_ALIGN (TREE_TYPE (linner)), word_mode,
                    lvolatilep);
  if (lnmode == VOIDmode)
    return 0;

  /* Set signed and unsigned types of the precision of this mode for the
     shifts below.  */
  signed_type = type_for_mode (lnmode, 0);
  unsigned_type = type_for_mode (lnmode, 1);

  if (! const_p)
    {
      rnmode = get_best_mode (rbitsize, rbitpos, 
                        TYPE_ALIGN (TREE_TYPE (rinner)), word_mode,
                        rvolatilep);
      if (rnmode == VOIDmode)
      return 0;
    }
    
  /* Compute the bit position and size for the new reference and our offset
     within it. If the new reference is the same size as the original, we
     won't optimize anything, so return zero.  */
  lnbitsize = GET_MODE_BITSIZE (lnmode);
  lnbitpos = lbitpos & ~ (lnbitsize - 1);
  lbitpos -= lnbitpos;
  if (lnbitsize == lbitsize)
    return 0;

  if (! const_p)
    {
      rnbitsize = GET_MODE_BITSIZE (rnmode);
      rnbitpos = rbitpos & ~ (rnbitsize - 1);
      rbitpos -= rnbitpos;
      if (rnbitsize == rbitsize)
      return 0;
    }

  if (BYTES_BIG_ENDIAN)
    lbitpos = lnbitsize - lbitsize - lbitpos;

  /* Make the mask to be used against the extracted field.  */
  mask = build_int_2 (~0, ~0);
  TREE_TYPE (mask) = unsigned_type;
  force_fit_type (mask, 0);
  mask = convert (unsigned_type, mask);
  mask = const_binop (LSHIFT_EXPR, mask, size_int (lnbitsize - lbitsize), 0);
  mask = const_binop (RSHIFT_EXPR, mask,
                  size_int (lnbitsize - lbitsize - lbitpos), 0);

  if (! const_p)
    /* If not comparing with constant, just rework the comparison
       and return.  */
    return build (code, compare_type,
              build (BIT_AND_EXPR, unsigned_type,
                   make_bit_field_ref (linner, unsigned_type,
                                   lnbitsize, lnbitpos, 1),
                   mask),
              build (BIT_AND_EXPR, unsigned_type,
                   make_bit_field_ref (rinner, unsigned_type,
                                   rnbitsize, rnbitpos, 1),
                   mask));

  /* Otherwise, we are handling the constant case. See if the constant is too
     big for the field.  Warn and return a tree of for 0 (false) if so.  We do
     this not only for its own sake, but to avoid having to test for this
     error case below.  If we didn't, we might generate wrong code.

     For unsigned fields, the constant shifted right by the field length should
     be all zero.  For signed fields, the high-order bits should agree with 
     the sign bit.  */

  if (lunsignedp)
    {
      if (! integer_zerop (const_binop (RSHIFT_EXPR,
                              convert (unsigned_type, rhs),
                              size_int (lbitsize), 0)))
      {
        warning ("comparison is always %s due to width of bitfield",
               code == NE_EXPR ? "one" : "zero");
        return convert (compare_type,
                    (code == NE_EXPR
                     ? integer_one_node : integer_zero_node));
      }
    }
  else
    {
      tree tem = const_binop (RSHIFT_EXPR, convert (signed_type, rhs),
                        size_int (lbitsize - 1), 0);
      if (! integer_zerop (tem) && ! integer_all_onesp (tem))
      {
        warning ("comparison is always %s due to width of bitfield",
               code == NE_EXPR ? "one" : "zero");
        return convert (compare_type,
                    (code == NE_EXPR
                     ? integer_one_node : integer_zero_node));
      }
    }

  /* Single-bit compares should always be against zero.  */
  if (lbitsize == 1 && ! integer_zerop (rhs))
    {
      code = code == EQ_EXPR ? NE_EXPR : EQ_EXPR;
      rhs = convert (type, integer_zero_node);
    }

  /* Make a new bitfield reference, shift the constant over the
     appropriate number of bits and mask it with the computed mask
     (in case this was a signed field).  If we changed it, make a new one.  */
  lhs = make_bit_field_ref (linner, unsigned_type, lnbitsize, lnbitpos, 1);
  if (lvolatilep)
    {
      TREE_SIDE_EFFECTS (lhs) = 1;
      TREE_THIS_VOLATILE (lhs) = 1;
    }

  rhs = fold (const_binop (BIT_AND_EXPR,
                     const_binop (LSHIFT_EXPR,
                              convert (unsigned_type, rhs),
                              size_int (lbitpos), 0),
                     mask, 0));

  return build (code, compare_type,
            build (BIT_AND_EXPR, unsigned_type, lhs, mask),
            rhs);
}

/* Subroutine for fold_truthop: decode a field reference.

   If EXP is a comparison reference, we return the innermost reference.

   *PBITSIZE is set to the number of bits in the reference, *PBITPOS is
   set to the starting bit number.

   If the innermost field can be completely contained in a mode-sized
   unit, *PMODE is set to that mode.  Otherwise, it is set to VOIDmode.

   *PVOLATILEP is set to 1 if the any expression encountered is volatile;
   otherwise it is not changed.

   *PUNSIGNEDP is set to the signedness of the field.

   *PMASK is set to the mask used.  This is either contained in a
   BIT_AND_EXPR or derived from the width of the field.

   *PAND_MASK is set to the mask found in a BIT_AND_EXPR, if any.

   Return 0 if this is not a component reference or is one that we can't
   do anything with.  */

static tree
decode_field_reference (exp, pbitsize, pbitpos, pmode, punsignedp,
                  pvolatilep, pmask, pand_mask)
     tree exp;
     int *pbitsize, *pbitpos;
     enum machine_mode *pmode;
     int *punsignedp, *pvolatilep;
     tree *pmask;
     tree *pand_mask;
{
  tree and_mask = 0;
  tree mask, inner, offset;
  tree unsigned_type;
  int precision;
  int alignment;

  /* All the optimizations using this function assume integer fields.  
     There are problems with FP fields since the type_for_size call
     below can fail for, e.g., XFmode.  */
  if (! INTEGRAL_TYPE_P (TREE_TYPE (exp)))
    return 0;

  STRIP_NOPS (exp);

  if (TREE_CODE (exp) == BIT_AND_EXPR)
    {
      and_mask = TREE_OPERAND (exp, 1);
      exp = TREE_OPERAND (exp, 0);
      STRIP_NOPS (exp); STRIP_NOPS (and_mask);
      if (TREE_CODE (and_mask) != INTEGER_CST)
      return 0;
    }


  inner = get_inner_reference (exp, pbitsize, pbitpos, &offset, pmode,
                         punsignedp, pvolatilep, &alignment);
  if ((inner == exp && and_mask == 0)
      || *pbitsize < 0 || offset != 0)
    return 0;
  
  /* Compute the mask to access the bitfield.  */
  unsigned_type = type_for_size (*pbitsize, 1);
  precision = TYPE_PRECISION (unsigned_type);

  mask = build_int_2 (~0, ~0);
  TREE_TYPE (mask) = unsigned_type;
  force_fit_type (mask, 0);
  mask = const_binop (LSHIFT_EXPR, mask, size_int (precision - *pbitsize), 0);
  mask = const_binop (RSHIFT_EXPR, mask, size_int (precision - *pbitsize), 0);

  /* Merge it with the mask we found in the BIT_AND_EXPR, if any.  */
  if (and_mask != 0)
    mask = fold (build (BIT_AND_EXPR, unsigned_type,
                  convert (unsigned_type, and_mask), mask));

  *pmask = mask;
  *pand_mask = and_mask;
  return inner;
}

/* Return non-zero if MASK represents a mask of SIZE ones in the low-order
   bit positions.  */

static int
all_ones_mask_p (mask, size)
     tree mask;
     int size;
{
  tree type = TREE_TYPE (mask);
  int precision = TYPE_PRECISION (type);
  tree tmask;

  tmask = build_int_2 (~0, ~0);
  TREE_TYPE (tmask) = signed_type (type);
  force_fit_type (tmask, 0);
  return
    tree_int_cst_equal (mask, 
                  const_binop (RSHIFT_EXPR,
                             const_binop (LSHIFT_EXPR, tmask,
                                      size_int (precision - size),
                                      0),
                             size_int (precision - size), 0));
}

/* Subroutine for fold_truthop: determine if an operand is simple enough
   to be evaluated unconditionally.  */

static int 
simple_operand_p (exp)
     tree exp;
{
  /* Strip any conversions that don't change the machine mode.  */
  while ((TREE_CODE (exp) == NOP_EXPR
        || TREE_CODE (exp) == CONVERT_EXPR)
       && (TYPE_MODE (TREE_TYPE (exp))
           == TYPE_MODE (TREE_TYPE (TREE_OPERAND (exp, 0)))))
    exp = TREE_OPERAND (exp, 0);

  return (TREE_CODE_CLASS (TREE_CODE (exp)) == 'c'
        || (TREE_CODE_CLASS (TREE_CODE (exp)) == 'd'
            && ! TREE_ADDRESSABLE (exp)
            && ! TREE_THIS_VOLATILE (exp)
            && ! DECL_NONLOCAL (exp)
            /* Don't regard global variables as simple.  They may be
             allocated in ways unknown to the compiler (shared memory,
             #pragma weak, etc).  */
            && ! TREE_PUBLIC (exp)
            && ! DECL_EXTERNAL (exp)
            /* Loading a static variable is unduly expensive, but global
             registers aren't expensive.  */
            && (! TREE_STATIC (exp) || DECL_REGISTER (exp))));
}

/* The following functions are subroutines to fold_range_test and allow it to
   try to change a logical combination of comparisons into a range test.

   For example, both
      X == 2 && X == 3 && X == 4 && X == 5
   and
      X >= 2 && X <= 5
   are converted to
      (unsigned) (X - 2) <= 3

   We describe each set of comparisons as being either inside or outside
   a range, using a variable named like IN_P, and then describe the
   range with a lower and upper bound.  If one of the bounds is omitted,
   it represents either the highest or lowest value of the type.

   In the comments below, we represent a range by two numbers in brackets
   preceded by a "+" to designate being inside that range, or a "-" to
   designate being outside that range, so the condition can be inverted by
   flipping the prefix.  An omitted bound is represented by a "-".  For
   example, "- [-, 10]" means being outside the range starting at the lowest
   possible value and ending at 10, in other words, being greater than 10.
   The range "+ [-, -]" is always true and hence the range "- [-, -]" is
   always false.

   We set up things so that the missing bounds are handled in a consistent
   manner so neither a missing bound nor "true" and "false" need to be
   handled using a special case.  */

/* Return the result of applying CODE to ARG0 and ARG1, but handle the case
   of ARG0 and/or ARG1 being omitted, meaning an unlimited range. UPPER0_P
   and UPPER1_P are nonzero if the respective argument is an upper bound
   and zero for a lower.  TYPE, if nonzero, is the type of the result; it
   must be specified for a comparison.  ARG1 will be converted to ARG0's
   type if both are specified.  */

static tree
range_binop (code, type, arg0, upper0_p, arg1, upper1_p)
     enum tree_code code;
     tree type;
     tree arg0, arg1;
     int upper0_p, upper1_p;
{
  tree tem;
  int result;
  int sgn0, sgn1;

  /* If neither arg represents infinity, do the normal operation.
     Else, if not a comparison, return infinity.  Else handle the special
     comparison rules. Note that most of the cases below won't occur, but
     are handled for consistency.  */

  if (arg0 != 0 && arg1 != 0)
    {
      tem = fold (build (code, type != 0 ? type : TREE_TYPE (arg0),
                   arg0, convert (TREE_TYPE (arg0), arg1)));
      STRIP_NOPS (tem);
      return TREE_CODE (tem) == INTEGER_CST ? tem : 0;
    }

  if (TREE_CODE_CLASS (code) != '<')
    return 0;

  /* Set SGN[01] to -1 if ARG[01] is a lower bound, 1 for upper, and 0
     for neither.  In real maths, we cannot assume open ended ranges are
     the same. But, this is computer arithmetic, where numbers are finite.
     We can therefore make the transformation of any unbounded range with
     the value Z, Z being greater than any representable number. This permits
     us to treat unbounded ranges as equal. */
  sgn0 = arg0 != 0 ? 0 : (upper0_p ? 1 : -1);
  sgn1 = arg1 != 0 ? 0 : (upper1_p ? 1 : -1);
  switch (code)
    {
    case EQ_EXPR:
      result = sgn0 == sgn1;
      break;
    case NE_EXPR:
      result = sgn0 != sgn1;
      break;
    case LT_EXPR:
      result = sgn0 < sgn1;
      break;
    case LE_EXPR:
      result = sgn0 <= sgn1;
      break;
    case GT_EXPR:
      result = sgn0 > sgn1;
      break;
    case GE_EXPR:
      result = sgn0 >= sgn1;
      break;
    default:
      abort ();
    }

  return convert (type, result ? integer_one_node : integer_zero_node);
}
      
/* Given EXP, a logical expression, set the range it is testing into
   variables denoted by PIN_P, PLOW, and PHIGH.  Return the expression
   actually being tested.  *PLOW and *PHIGH will have be made the same type
   as the returned expression.  If EXP is not a comparison, we will most
   likely not be returning a useful value and range.  */

static tree
make_range (exp, pin_p, plow, phigh)
     tree exp;
     int *pin_p;
     tree *plow, *phigh;
{
  enum tree_code code;
  tree arg0, arg1, type = NULL_TREE;
  tree orig_type = NULL_TREE;
  int in_p, n_in_p;
  tree low, high, n_low, n_high;

  /* Start with simply saying "EXP != 0" and then look at the code of EXP
     and see if we can refine the range.  Some of the cases below may not
     happen, but it doesn't seem worth worrying about this.  We "continue"
     the outer loop when we've changed something; otherwise we "break"
     the switch, which will "break" the while.  */

  in_p = 0, low = high = convert (TREE_TYPE (exp), integer_zero_node);

  while (1)
    {
      code = TREE_CODE (exp);

      if (IS_EXPR_CODE_CLASS (TREE_CODE_CLASS (code)))
      {
        arg0 = TREE_OPERAND (exp, 0);
        if (TREE_CODE_CLASS (code) == '<' 
            || TREE_CODE_CLASS (code) == '1'
            || TREE_CODE_CLASS (code) == '2')
          type = TREE_TYPE (arg0);
        if (TREE_CODE_CLASS (code) == '2' 
            || TREE_CODE_CLASS (code) == '<'
            || (TREE_CODE_CLASS (code) == 'e' 
              && tree_code_length[(int) code] > 1))
          arg1 = TREE_OPERAND (exp, 1);
      }

      switch (code)
      {
      case TRUTH_NOT_EXPR:
        in_p = ! in_p, exp = arg0;
        continue;

      case EQ_EXPR: case NE_EXPR:
      case LT_EXPR: case LE_EXPR: case GE_EXPR: case GT_EXPR:
        /* We can only do something if the range is testing for zero
           and if the second operand is an integer constant.  Note that
           saying something is "in" the range we make is done by
           complementing IN_P since it will set in the initial case of
           being not equal to zero; "out" is leaving it alone.  */
        if (low == 0 || high == 0
            || ! integer_zerop (low) || ! integer_zerop (high)
            || TREE_CODE (arg1) != INTEGER_CST)
          break;

        switch (code)
          {
          case NE_EXPR:  /* - [c, c]  */
            low = high = arg1;
            break;
          case EQ_EXPR:  /* + [c, c]  */
            in_p = ! in_p, low = high = arg1;
            break;
          case GT_EXPR:  /* - [-, c] */
            low = 0, high = arg1;
            break;
          case GE_EXPR:  /* + [c, -] */
            in_p = ! in_p, low = arg1, high = 0;
            break;
          case LT_EXPR:  /* - [c, -] */
            low = arg1, high = 0;
            break;
          case LE_EXPR:  /* + [-, c] */
            in_p = ! in_p, low = 0, high = arg1;
            break;
          default:
            abort ();
          }

        exp = arg0;

        /* If this is an unsigned comparison, we also know that EXP is
           greater than or equal to zero.  We base the range tests we make
           on that fact, so we record it here so we can parse existing
           range tests.  */
        if (TREE_UNSIGNED (type) && (low == 0 || high == 0))
          {
            if (! merge_ranges (&n_in_p, &n_low, &n_high, in_p, low, high,
                          1, convert (type, integer_zero_node),
                          NULL_TREE))
            break;

            in_p = n_in_p, low = n_low, high = n_high;

            /* If the high bound is missing, reverse the range so it
             goes from zero to the low bound minus 1.  */
            if (high == 0)
            {
              in_p = ! in_p;
              high = range_binop (MINUS_EXPR, NULL_TREE, low, 0,
                              integer_one_node, 0);
              low = convert (type, integer_zero_node);
            }
          }
        continue;

      case NEGATE_EXPR:
        /* (-x) IN [a,b] -> x in [-b, -a]  */
        n_low = range_binop (MINUS_EXPR, type,
                         convert (type, integer_zero_node), 0, high, 1);
        n_high = range_binop (MINUS_EXPR, type,
                        convert (type, integer_zero_node), 0, low, 0);
        low = n_low, high = n_high;
        exp = arg0;
        continue;

      case BIT_NOT_EXPR:
        /* ~ X -> -X - 1  */
        exp = build (MINUS_EXPR, type, build1 (NEGATE_EXPR, type, arg0),
                   convert (type, integer_one_node));
        continue;

      case PLUS_EXPR:  case MINUS_EXPR:
        if (TREE_CODE (arg1) != INTEGER_CST)
          break;

        /* If EXP is signed, any overflow in the computation is undefined,
           so we don't worry about it so long as our computations on
           the bounds don't overflow.  For unsigned, overflow is defined
           and this is exactly the right thing.  */
        n_low = range_binop (code == MINUS_EXPR ? PLUS_EXPR : MINUS_EXPR,
                         type, low, 0, arg1, 0);
        n_high = range_binop (code == MINUS_EXPR ? PLUS_EXPR : MINUS_EXPR,
                        type, high, 1, arg1, 0);
        if ((n_low != 0 && TREE_OVERFLOW (n_low))
            || (n_high != 0 && TREE_OVERFLOW (n_high)))
          break;

        /* Check for an unsigned range which has wrapped around the maximum
           value thus making n_high < n_low, and normalize it.  */
        if (n_low && n_high && tree_int_cst_lt (n_high, n_low))
          {
            low = range_binop (PLUS_EXPR, type, n_high, 0,
                         integer_one_node, 0);
            high = range_binop (MINUS_EXPR, type, n_low, 0,
                         integer_one_node, 0);
            in_p = ! in_p;
          }
        else
          low = n_low, high = n_high;

        exp = arg0;
        continue;

      case NOP_EXPR:  case NON_LVALUE_EXPR:  case CONVERT_EXPR:
        if (orig_type == NULL_TREE)
          orig_type = type;
        if (TYPE_PRECISION (type) > TYPE_PRECISION (orig_type))
          break;

        if (! INTEGRAL_TYPE_P (type)
            || (low != 0 && ! int_fits_type_p (low, type))
            || (high != 0 && ! int_fits_type_p (high, type)))
          break;

        n_low = low, n_high = high;

        if (n_low != 0)
          n_low = convert (type, n_low);

        if (n_high != 0)
          n_high = convert (type, n_high);

        /* If we're converting from an unsigned to a signed type,
           we will be doing the comparison as unsigned.  The tests above
           have already verified that LOW and HIGH are both positive.

           So we have to make sure that the original unsigned value will
           be interpreted as positive.  */
        if (TREE_UNSIGNED (type) && ! TREE_UNSIGNED (TREE_TYPE (exp)))
          {
            tree equiv_type = type_for_mode (TYPE_MODE (type), 1);
            tree high_positive;

            /* A range without an upper bound is, naturally, unbounded.
             Since convert would have cropped a very large value, use
              the max value for the destination type.  */

            high_positive = TYPE_MAX_VALUE (equiv_type);
            if (!high_positive)
            {
              high_positive = TYPE_MAX_VALUE (type);
              if (!high_positive)
                abort();
            }
            high_positive = fold (build (RSHIFT_EXPR, type,
                                 convert (type, high_positive),
                                 convert (type, integer_one_node)));
                  
            /* If the low bound is specified, "and" the range with the
             range for which the original unsigned value will be
             positive.  */
            if (low != 0)
            {
              if (! merge_ranges (&n_in_p, &n_low, &n_high,
                              1, n_low, n_high,
                              1, convert (type, integer_zero_node),
                              high_positive))
                break;

              in_p = (n_in_p == in_p);
            }
            else
            {
              /* Otherwise, "or" the range with the range of the input
                 that will be interpreted as negative.  */
              if (! merge_ranges (&n_in_p, &n_low, &n_high,
                              0, n_low, n_high,
                              1, convert (type, integer_zero_node),
                              high_positive))
                break;

              in_p = (in_p != n_in_p);
            }
          }

        exp = arg0;
        low = n_low, high = n_high;
        continue;

      default:
        break;
      }

      break;
    }

  /* If EXP is a constant, we can evaluate whether this is true or false.  */
  if (TREE_CODE (exp) == INTEGER_CST)
    {
      in_p = in_p == (integer_onep (range_binop (GE_EXPR, integer_type_node,
                                     exp, 0, low, 0))
                  && integer_onep (range_binop (LE_EXPR, integer_type_node,
                                        exp, 1, high, 1)));
      low = high = 0;
      exp = 0;
    }

  *pin_p = in_p, *plow = low, *phigh = high;
  return exp;
}

/* Given a range, LOW, HIGH, and IN_P, an expression, EXP, and a result
   type, TYPE, return an expression to test if EXP is in (or out of, depending
   on IN_P) the range.  */

static tree
build_range_check (type, exp, in_p, low, high)
     tree type;
     tree exp;
     int in_p;
     tree low, high;
{
  tree etype = TREE_TYPE (exp);
  tree utype, value;

  if (! in_p
      && (0 != (value = build_range_check (type, exp, 1, low, high))))
    return invert_truthvalue (value);

  else if (low == 0 && high == 0)
    return convert (type, integer_one_node);

  else if (low == 0)
    return fold (build (LE_EXPR, type, exp, high));

  else if (high == 0)
    return fold (build (GE_EXPR, type, exp, low));

  else if (operand_equal_p (low, high, 0))
    return fold (build (EQ_EXPR, type, exp, low));

  else if (TREE_UNSIGNED (etype) && integer_zerop (low))
    return build_range_check (type, exp, 1, 0, high);

  else if (integer_zerop (low))
    {
      utype = unsigned_type (etype);
      return build_range_check (type, convert (utype, exp), 1, 0,
                        convert (utype, high));
    }

  else if (0 != (value = const_binop (MINUS_EXPR, high, low, 0))
         && ! TREE_OVERFLOW (value))
    return build_range_check (type,
                        fold (build (MINUS_EXPR, etype, exp, low)),
                        1, convert (etype, integer_zero_node), value);
  else
    return 0;
}

/* Given two ranges, see if we can merge them into one.  Return 1 if we 
   can, 0 if we can't.  Set the output range into the specified parameters.  */

static int
merge_ranges (pin_p, plow, phigh, in0_p, low0, high0, in1_p, low1, high1)
     int *pin_p;
     tree *plow, *phigh;
     int in0_p, in1_p;
     tree low0, high0, low1, high1;
{
  int no_overlap;
  int subset;
  int temp;
  tree tem;
  int in_p;
  tree low, high;
  int lowequal = ((low0 == 0 && low1 == 0)
              || integer_onep (range_binop (EQ_EXPR, integer_type_node,
                                    low0, 0, low1, 0)));
  int highequal = ((high0 == 0 && high1 == 0)
               || integer_onep (range_binop (EQ_EXPR, integer_type_node,
                                     high0, 1, high1, 1)));

  /* Make range 0 be the range that starts first, or ends last if they
     start at the same value.  Swap them if it isn't.  */
  if (integer_onep (range_binop (GT_EXPR, integer_type_node, 
                         low0, 0, low1, 0))
      || (lowequal
        && integer_onep (range_binop (GT_EXPR, integer_type_node,
                              high1, 1, high0, 1))))
    {
      temp = in0_p, in0_p = in1_p, in1_p = temp;
      tem = low0, low0 = low1, low1 = tem;
      tem = high0, high0 = high1, high1 = tem;
    }

  /* Now flag two cases, whether the ranges are disjoint or whether the
     second range is totally subsumed in the first.  Note that the tests
     below are simplified by the ones above.  */
  no_overlap = integer_onep (range_binop (LT_EXPR, integer_type_node,
                                high0, 1, low1, 0));
  subset = integer_onep (range_binop (LE_EXPR, integer_type_node,
                              high1, 1, high0, 1));

  /* We now have four cases, depending on whether we are including or
     excluding the two ranges.  */
  if (in0_p && in1_p)
    {
      /* If they don't overlap, the result is false.  If the second range
       is a subset it is the result.  Otherwise, the range is from the start
       of the second to the end of the first.  */
      if (no_overlap)
      in_p = 0, low = high = 0;
      else if (subset)
      in_p = 1, low = low1, high = high1;
      else
      in_p = 1, low = low1, high = high0;
    }

  else if (in0_p && ! in1_p)
    {
      /* If they don't overlap, the result is the first range.  If they are
       equal, the result is false.  If the second range is a subset of the
       first, and the ranges begin at the same place, we go from just after
       the end of the first range to the end of the second.  If the second
       range is not a subset of the first, or if it is a subset and both
       ranges end at the same place, the range starts at the start of the
       first range and ends just before the second range.
       Otherwise, we can't describe this as a single range.  */
      if (no_overlap)
      in_p = 1, low = low0, high = high0;
      else if (lowequal && highequal)
      in_p = 0, low = high = 0;
      else if (subset && lowequal)
      {
        in_p = 1, high = high0;
        low = range_binop (PLUS_EXPR, NULL_TREE, high1, 0,
                       integer_one_node, 0);      
      }
      else if (! subset || highequal)
      {
        in_p = 1, low = low0;
        high = range_binop (MINUS_EXPR, NULL_TREE, low1, 0,
                        integer_one_node, 0);
      }
      else
      return 0;
    }

  else if (! in0_p && in1_p)
    {
      /* If they don't overlap, the result is the second range.  If the second
       is a subset of the first, the result is false.  Otherwise,
       the range starts just after the first range and ends at the
       end of the second.  */
      if (no_overlap)
      in_p = 1, low = low1, high = high1;
      else if (subset)
      in_p = 0, low = high = 0;
      else
      {
        in_p = 1, high = high1;
        low = range_binop (PLUS_EXPR, NULL_TREE, high0, 1,
                       integer_one_node, 0);
      }
    }

  else
    {
      /* The case where we are excluding both ranges.  Here the complex case
       is if they don't overlap.  In that case, the only time we have a
       range is if they are adjacent.  If the second is a subset of the
       first, the result is the first.  Otherwise, the range to exclude
       starts at the beginning of the first range and ends at the end of the
       second.  */
      if (no_overlap)
      {
        if (integer_onep (range_binop (EQ_EXPR, integer_type_node,
                               range_binop (PLUS_EXPR, NULL_TREE,
                                          high0, 1,
                                          integer_one_node, 1),
                               1, low1, 0)))
          in_p = 0, low = low0, high = high1;
        else
          return 0;
      }
      else if (subset)
      in_p = 0, low = low0, high = high0;
      else
      in_p = 0, low = low0, high = high1;
    }

  *pin_p = in_p, *plow = low, *phigh = high;
  return 1;
}

/* EXP is some logical combination of boolean tests.  See if we can
   merge it into some range test.  Return the new tree if so.  */

static tree
fold_range_test (exp)
     tree exp;
{
  int or_op = (TREE_CODE (exp) == TRUTH_ORIF_EXPR
             || TREE_CODE (exp) == TRUTH_OR_EXPR);
  int in0_p, in1_p, in_p;
  tree low0, low1, low, high0, high1, high;
  tree lhs = make_range (TREE_OPERAND (exp, 0), &in0_p, &low0, &high0);
  tree rhs = make_range (TREE_OPERAND (exp, 1), &in1_p, &low1, &high1);
  tree tem;

  /* If this is an OR operation, invert both sides; we will invert
     again at the end.  */
  if (or_op)
    in0_p = ! in0_p, in1_p = ! in1_p;

  /* If both expressions are the same, if we can merge the ranges, and we
     can build the range test, return it or it inverted.  If one of the
     ranges is always true or always false, consider it to be the same
     expression as the other.  */
  if ((lhs == 0 || rhs == 0 || operand_equal_p (lhs, rhs, 0))
      && merge_ranges (&in_p, &low, &high, in0_p, low0, high0,
                   in1_p, low1, high1)
      && 0 != (tem = (build_range_check (TREE_TYPE (exp),
                               lhs != 0 ? lhs
                               : rhs != 0 ? rhs : integer_zero_node,
                               in_p, low, high))))
    return or_op ? invert_truthvalue (tem) : tem;

  /* On machines where the branch cost is expensive, if this is a
     short-circuited branch and the underlying object on both sides
     is the same, make a non-short-circuit operation.  */
  else if (BRANCH_COST >= 2
         && (TREE_CODE (exp) == TRUTH_ANDIF_EXPR
             || TREE_CODE (exp) == TRUTH_ORIF_EXPR)
         && operand_equal_p (lhs, rhs, 0))
    {
      /* If simple enough, just rewrite.  Otherwise, make a SAVE_EXPR
       unless we are at top level or LHS contains a PLACEHOLDER_EXPR, in
       which cases we can't do this.  */
      if (simple_operand_p (lhs))
      return build (TREE_CODE (exp) == TRUTH_ANDIF_EXPR
                  ? TRUTH_AND_EXPR : TRUTH_OR_EXPR,
                  TREE_TYPE (exp), TREE_OPERAND (exp, 0),
                  TREE_OPERAND (exp, 1));

      else if (current_function_decl != 0
             && ! contains_placeholder_p (lhs))
      {
        tree common = save_expr (lhs);

        if (0 != (lhs = build_range_check (TREE_TYPE (exp), common,
                                   or_op ? ! in0_p : in0_p,
                                   low0, high0))
            && (0 != (rhs = build_range_check (TREE_TYPE (exp), common,
                                     or_op ? ! in1_p : in1_p,
                                     low1, high1))))
          return build (TREE_CODE (exp) == TRUTH_ANDIF_EXPR
                    ? TRUTH_AND_EXPR : TRUTH_OR_EXPR,
                    TREE_TYPE (exp), lhs, rhs);
      }
    }


  return 0;
}

/* Subroutine for fold_truthop: C is an INTEGER_CST interpreted as a P
   bit value.  Arrange things so the extra bits will be set to zero if and
   only if C is signed-extended to its full width.  If MASK is nonzero,
   it is an INTEGER_CST that should be AND'ed with the extra bits.  */

static tree
unextend (c, p, unsignedp, mask)
     tree c;
     int p;
     int unsignedp;
     tree mask;
{
  tree type = TREE_TYPE (c);
  int modesize = GET_MODE_BITSIZE (TYPE_MODE (type));
  tree temp;

  if (p == modesize || unsignedp)
    return c;

  /* We work by getting just the sign bit into the low-order bit, then
     into the high-order bit, then sign-extend.  We then XOR that value
     with C.  */
  temp = const_binop (RSHIFT_EXPR, c, size_int (p - 1), 0);
  temp = const_binop (BIT_AND_EXPR, temp, size_int (1), 0);

  /* We must use a signed type in order to get an arithmetic right shift.
     However, we must also avoid introducing accidental overflows, so that
     a subsequent call to integer_zerop will work.  Hence we must 
     do the type conversion here.  At this point, the constant is either
     zero or one, and the conversion to a signed type can never overflow.
     We could get an overflow if this conversion is done anywhere else.  */
  if (TREE_UNSIGNED (type))
    temp = convert (signed_type (type), temp);

  temp = const_binop (LSHIFT_EXPR, temp, size_int (modesize - 1), 0);
  temp = const_binop (RSHIFT_EXPR, temp, size_int (modesize - p - 1), 0);
  if (mask != 0)
    temp = const_binop (BIT_AND_EXPR, temp, convert (TREE_TYPE (c), mask), 0);
  /* If necessary, convert the type back to match the type of C.  */
  if (TREE_UNSIGNED (type))
    temp = convert (type, temp);

  return convert (type, const_binop (BIT_XOR_EXPR, c, temp, 0));
}

/* Find ways of folding logical expressions of LHS and RHS:
   Try to merge two comparisons to the same innermost item.
   Look for range tests like "ch >= '0' && ch <= '9'".
   Look for combinations of simple terms on machines with expensive branches
   and evaluate the RHS unconditionally.

   For example, if we have p->a == 2 && p->b == 4 and we can make an
   object large enough to span both A and B, we can do this with a comparison
   against the object ANDed with the a mask.

   If we have p->a == q->a && p->b == q->b, we may be able to use bit masking
   operations to do this with one comparison.

   We check for both normal comparisons and the BIT_AND_EXPRs made this by
   function and the one above.

   CODE is the logical operation being done.  It can be TRUTH_ANDIF_EXPR,
   TRUTH_AND_EXPR, TRUTH_ORIF_EXPR, or TRUTH_OR_EXPR.

   TRUTH_TYPE is the type of the logical operand and LHS and RHS are its
   two operands.

   We return the simplified tree or 0 if no optimization is possible.  */

static tree
fold_truthop (code, truth_type, lhs, rhs)
     enum tree_code code;
     tree truth_type, lhs, rhs;
{
  /* If this is the "or" of two comparisons, we can do something if we
     the comparisons are NE_EXPR.  If this is the "and", we can do something
     if the comparisons are EQ_EXPR.  I.e., 
      (a->b == 2 && a->c == 4) can become (a->new == NEW).

     WANTED_CODE is this operation code.  For single bit fields, we can
     convert EQ_EXPR to NE_EXPR so we need not reject the "wrong"
     comparison for one-bit fields.  */

  enum tree_code wanted_code;
  enum tree_code lcode, rcode;
  tree ll_arg, lr_arg, rl_arg, rr_arg;
  tree ll_inner, lr_inner, rl_inner, rr_inner;
  int ll_bitsize, ll_bitpos, lr_bitsize, lr_bitpos;
  int rl_bitsize, rl_bitpos, rr_bitsize, rr_bitpos;
  int xll_bitpos, xlr_bitpos, xrl_bitpos, xrr_bitpos;
  int lnbitsize, lnbitpos, rnbitsize, rnbitpos;
  int ll_unsignedp, lr_unsignedp, rl_unsignedp, rr_unsignedp;
  enum machine_mode ll_mode, lr_mode, rl_mode, rr_mode;
  enum machine_mode lnmode, rnmode;
  tree ll_mask, lr_mask, rl_mask, rr_mask;
  tree ll_and_mask, lr_and_mask, rl_and_mask, rr_and_mask;
  tree l_const, r_const;
  tree type, result;
  int first_bit, end_bit;
  int volatilep;

  /* Start by getting the comparison codes.  Fail if anything is volatile.
     If one operand is a BIT_AND_EXPR with the constant one, treat it as if
     it were surrounded with a NE_EXPR.  */

  if (TREE_SIDE_EFFECTS (lhs) || TREE_SIDE_EFFECTS (rhs))
    return 0;

  lcode = TREE_CODE (lhs);
  rcode = TREE_CODE (rhs);

  if (lcode == BIT_AND_EXPR && integer_onep (TREE_OPERAND (lhs, 1)))
    lcode = NE_EXPR, lhs = build (NE_EXPR, truth_type, lhs, integer_zero_node);

  if (rcode == BIT_AND_EXPR && integer_onep (TREE_OPERAND (rhs, 1)))
    rcode = NE_EXPR, rhs = build (NE_EXPR, truth_type, rhs, integer_zero_node);

  if (TREE_CODE_CLASS (lcode) != '<' || TREE_CODE_CLASS (rcode) != '<')
    return 0;

  code = ((code == TRUTH_AND_EXPR || code == TRUTH_ANDIF_EXPR)
        ? TRUTH_AND_EXPR : TRUTH_OR_EXPR);

  ll_arg = TREE_OPERAND (lhs, 0);
  lr_arg = TREE_OPERAND (lhs, 1);
  rl_arg = TREE_OPERAND (rhs, 0);
  rr_arg = TREE_OPERAND (rhs, 1);
  
  /* If the RHS can be evaluated unconditionally and its operands are
     simple, it wins to evaluate the RHS unconditionally on machines
     with expensive branches.  In this case, this isn't a comparison
     that can be merged.  */

  /* @@ I'm not sure it wins on the m88110 to do this if the comparisons
     are with zero (tmw).  */

  if (BRANCH_COST >= 2
      && INTEGRAL_TYPE_P (TREE_TYPE (rhs))
      && simple_operand_p (rl_arg)
      && simple_operand_p (rr_arg))
    return build (code, truth_type, lhs, rhs);

  /* See if the comparisons can be merged.  Then get all the parameters for
     each side.  */

  if ((lcode != EQ_EXPR && lcode != NE_EXPR)
      || (rcode != EQ_EXPR && rcode != NE_EXPR))
    return 0;

  volatilep = 0;
  ll_inner = decode_field_reference (ll_arg,
                             &ll_bitsize, &ll_bitpos, &ll_mode,
                             &ll_unsignedp, &volatilep, &ll_mask,
                             &ll_and_mask);
  lr_inner = decode_field_reference (lr_arg,
                             &lr_bitsize, &lr_bitpos, &lr_mode,
                             &lr_unsignedp, &volatilep, &lr_mask,
                             &lr_and_mask);
  rl_inner = decode_field_reference (rl_arg,
                             &rl_bitsize, &rl_bitpos, &rl_mode,
                             &rl_unsignedp, &volatilep, &rl_mask,
                             &rl_and_mask);
  rr_inner = decode_field_reference (rr_arg,
                             &rr_bitsize, &rr_bitpos, &rr_mode,
                             &rr_unsignedp, &volatilep, &rr_mask,
                             &rr_and_mask);

  /* It must be true that the inner operation on the lhs of each
     comparison must be the same if we are to be able to do anything.
     Then see if we have constants.  If not, the same must be true for
     the rhs's.  */
  if (volatilep || ll_inner == 0 || rl_inner == 0
      || ! operand_equal_p (ll_inner, rl_inner, 0))
    return 0;

  if (TREE_CODE (lr_arg) == INTEGER_CST
      && TREE_CODE (rr_arg) == INTEGER_CST)
    l_const = lr_arg, r_const = rr_arg;
  else if (lr_inner == 0 || rr_inner == 0
         || ! operand_equal_p (lr_inner, rr_inner, 0))
    return 0;
  else
    l_const = r_const = 0;

  /* If either comparison code is not correct for our logical operation,
     fail.  However, we can convert a one-bit comparison against zero into
     the opposite comparison against that bit being set in the field.  */

  wanted_code = (code == TRUTH_AND_EXPR ? EQ_EXPR : NE_EXPR);
  if (lcode != wanted_code)
    {
      if (l_const && integer_zerop (l_const) && integer_pow2p (ll_mask))
      {
        if (ll_unsignedp || tree_log2 (ll_mask) + 1 < ll_bitsize)
          l_const = ll_mask;
      else
        /* Since ll_arg is a single bit bit mask, we can sign extend
           it appropriately with a NEGATE_EXPR.
           l_const is made a signed value here, but since for l_const != NULL
           lr_unsignedp is not used, we don't need to clear the latter.  */
        l_const = fold (build1 (NEGATE_EXPR, TREE_TYPE (ll_arg),
                          convert (TREE_TYPE (ll_arg), ll_mask)));
      }
      else
      return 0;
    }

  if (rcode != wanted_code)
    {
      if (r_const && integer_zerop (r_const) && integer_pow2p (rl_mask))
      {
        if (rl_unsignedp || tree_log2 (rl_mask) + 1 < rl_bitsize)
          r_const = rl_mask;
      else
        /* This is analogous to the code for l_const above.  */
        r_const = fold (build1 (NEGATE_EXPR, TREE_TYPE (rl_arg),
                          convert (TREE_TYPE (rl_arg), rl_mask)));
      }
      else
      return 0;
    }

  /* See if we can find a mode that contains both fields being compared on
     the left.  If we can't, fail.  Otherwise, update all constants and masks
     to be relative to a field of that size.  */
  first_bit = MIN (ll_bitpos, rl_bitpos);
  end_bit = MAX (ll_bitpos + ll_bitsize, rl_bitpos + rl_bitsize);
  lnmode = get_best_mode (end_bit - first_bit, first_bit,
                    TYPE_ALIGN (TREE_TYPE (ll_inner)), word_mode,
                    volatilep);
  if (lnmode == VOIDmode)
    return 0;

  lnbitsize = GET_MODE_BITSIZE (lnmode);
  lnbitpos = first_bit & ~ (lnbitsize - 1);
  type = type_for_size (lnbitsize, 1);
  xll_bitpos = ll_bitpos - lnbitpos, xrl_bitpos = rl_bitpos - lnbitpos;

  if (BYTES_BIG_ENDIAN)
    {
      xll_bitpos = lnbitsize - xll_bitpos - ll_bitsize;
      xrl_bitpos = lnbitsize - xrl_bitpos - rl_bitsize;
    }

  ll_mask = const_binop (LSHIFT_EXPR, convert (type, ll_mask),
                   size_int (xll_bitpos), 0);
  rl_mask = const_binop (LSHIFT_EXPR, convert (type, rl_mask),
                   size_int (xrl_bitpos), 0);

  if (l_const)
    {
      l_const = convert (type, l_const);
      l_const = unextend (l_const,  ll_bitsize, ll_unsignedp, ll_and_mask);
      l_const = const_binop (LSHIFT_EXPR, l_const, size_int (xll_bitpos), 0);
      if (! integer_zerop (const_binop (BIT_AND_EXPR, l_const,
                              fold (build1 (BIT_NOT_EXPR,
                                          type, ll_mask)),
                              0)))
      {
        warning ("comparison is always %s",
               wanted_code == NE_EXPR ? "one" : "zero");
        
        return convert (truth_type,
                    wanted_code == NE_EXPR
                    ? integer_one_node : integer_zero_node);
      }
    }
  if (r_const)
    {
      r_const = convert (type, r_const);
      r_const = unextend (r_const, rl_bitsize, rl_unsignedp, rl_and_mask);
      r_const = const_binop (LSHIFT_EXPR, r_const, size_int (xrl_bitpos), 0);
      if (! integer_zerop (const_binop (BIT_AND_EXPR, r_const,
                              fold (build1 (BIT_NOT_EXPR,
                                          type, rl_mask)),
                              0)))
      {
        warning ("comparison is always %s",
               wanted_code == NE_EXPR ? "one" : "zero");
        
        return convert (truth_type,
                    wanted_code == NE_EXPR
                    ? integer_one_node : integer_zero_node);
      }
    }

  /* If the right sides are not constant, do the same for it.  Also,
     disallow this optimization if a size or signedness mismatch occurs
     between the left and right sides.  */
  if (l_const == 0)
    {
      if (ll_bitsize != lr_bitsize || rl_bitsize != rr_bitsize
        || ll_unsignedp != lr_unsignedp || rl_unsignedp != rr_unsignedp
        /* Make sure the two fields on the right
           correspond to the left without being swapped.  */
        || ll_bitpos - rl_bitpos != lr_bitpos - rr_bitpos)
      return 0;

      first_bit = MIN (lr_bitpos, rr_bitpos);
      end_bit = MAX (lr_bitpos + lr_bitsize, rr_bitpos + rr_bitsize);
      rnmode = get_best_mode (end_bit - first_bit, first_bit,
                        TYPE_ALIGN (TREE_TYPE (lr_inner)), word_mode,
                        volatilep);
      if (rnmode == VOIDmode)
      return 0;

      rnbitsize = GET_MODE_BITSIZE (rnmode);
      rnbitpos = first_bit & ~ (rnbitsize - 1);
      xlr_bitpos = lr_bitpos - rnbitpos, xrr_bitpos = rr_bitpos - rnbitpos;

      if (BYTES_BIG_ENDIAN)
      {
        xlr_bitpos = rnbitsize - xlr_bitpos - lr_bitsize;
        xrr_bitpos = rnbitsize - xrr_bitpos - rr_bitsize;
      }

      lr_mask = const_binop (LSHIFT_EXPR, convert (type, lr_mask),
                       size_int (xlr_bitpos), 0);
      rr_mask = const_binop (LSHIFT_EXPR, convert (type, rr_mask),
                       size_int (xrr_bitpos), 0);

      /* Make a mask that corresponds to both fields being compared.
       Do this for both items being compared.  If the masks agree,
       we can do this by masking both and comparing the masked
       results.  */
      ll_mask = const_binop (BIT_IOR_EXPR, ll_mask, rl_mask, 0);
      lr_mask = const_binop (BIT_IOR_EXPR, lr_mask, rr_mask, 0);
      if (operand_equal_p (ll_mask, lr_mask, 0) && lnbitsize == rnbitsize)
      {
        lhs = make_bit_field_ref (ll_inner, type, lnbitsize, lnbitpos,
                            ll_unsignedp || rl_unsignedp);
        rhs = make_bit_field_ref (lr_inner, type, rnbitsize, rnbitpos,
                            lr_unsignedp || rr_unsignedp);
        if (! all_ones_mask_p (ll_mask, lnbitsize))
          {
            lhs = build (BIT_AND_EXPR, type, lhs, ll_mask);
            rhs = build (BIT_AND_EXPR, type, rhs, ll_mask);
          }
        return build (wanted_code, truth_type, lhs, rhs);
      }

      /* There is still another way we can do something:  If both pairs of
       fields being compared are adjacent, we may be able to make a wider
       field containing them both.  */
      if ((ll_bitsize + ll_bitpos == rl_bitpos
         && lr_bitsize + lr_bitpos == rr_bitpos)
        || (ll_bitpos == rl_bitpos + rl_bitsize
            && lr_bitpos == rr_bitpos + rr_bitsize))
      return build (wanted_code, truth_type,
                  make_bit_field_ref (ll_inner, type,
                                ll_bitsize + rl_bitsize,
                                MIN (ll_bitpos, rl_bitpos),
                                ll_unsignedp),
                  make_bit_field_ref (lr_inner, type,
                                lr_bitsize + rr_bitsize,
                                MIN (lr_bitpos, rr_bitpos),
                                lr_unsignedp));

      return 0;
    }

  /* Handle the case of comparisons with constants.  If there is something in
     common between the masks, those bits of the constants must be the same.
     If not, the condition is always false.  Test for this to avoid generating
     incorrect code below.  */
  result = const_binop (BIT_AND_EXPR, ll_mask, rl_mask, 0);
  if (! integer_zerop (result)
      && simple_cst_equal (const_binop (BIT_AND_EXPR, result, l_const, 0),
                     const_binop (BIT_AND_EXPR, result, r_const, 0)) != 1)
    {
      if (wanted_code == NE_EXPR)
      {
        warning ("`or' of unmatched not-equal tests is always 1");
        return convert (truth_type, integer_one_node);
      }
      else
      {
        warning ("`and' of mutually exclusive equal-tests is always zero");
        return convert (truth_type, integer_zero_node);
      }
    }

  /* Construct the expression we will return.  First get the component
     reference we will make.  Unless the mask is all ones the width of
     that field, perform the mask operation.  Then compare with the
     merged constant.  */
  result = make_bit_field_ref (ll_inner, type, lnbitsize, lnbitpos,
                         ll_unsignedp || rl_unsignedp);

  ll_mask = const_binop (BIT_IOR_EXPR, ll_mask, rl_mask, 0);
  if (! all_ones_mask_p (ll_mask, lnbitsize))
    result = build (BIT_AND_EXPR, type, result, ll_mask);

  return build (wanted_code, truth_type, result,
            const_binop (BIT_IOR_EXPR, l_const, r_const, 0));
}

/* If T contains a COMPOUND_EXPR which was inserted merely to evaluate
   S, a SAVE_EXPR, return the expression actually being evaluated.   Note
   that we may sometimes modify the tree.  */

static tree
strip_compound_expr (t, s)
     tree t;
     tree s;
{
  enum tree_code code = TREE_CODE (t);

  /* See if this is the COMPOUND_EXPR we want to eliminate.  */
  if (code == COMPOUND_EXPR && TREE_CODE (TREE_OPERAND (t, 0)) == CONVERT_EXPR
      && TREE_OPERAND (TREE_OPERAND (t, 0), 0) == s)
    return TREE_OPERAND (t, 1);

  /* See if this is a COND_EXPR or a simple arithmetic operator.   We
     don't bother handling any other types.  */
  else if (code == COND_EXPR)
    {
      TREE_OPERAND (t, 0) = strip_compound_expr (TREE_OPERAND (t, 0), s);
      TREE_OPERAND (t, 1) = strip_compound_expr (TREE_OPERAND (t, 1), s);
      TREE_OPERAND (t, 2) = strip_compound_expr (TREE_OPERAND (t, 2), s);
    }
  else if (TREE_CODE_CLASS (code) == '1')
    TREE_OPERAND (t, 0) = strip_compound_expr (TREE_OPERAND (t, 0), s);
  else if (TREE_CODE_CLASS (code) == '<'
         || TREE_CODE_CLASS (code) == '2')
    {
      TREE_OPERAND (t, 0) = strip_compound_expr (TREE_OPERAND (t, 0), s);
      TREE_OPERAND (t, 1) = strip_compound_expr (TREE_OPERAND (t, 1), s);
    }

  return t;
}

/* Return a node which has the indicated constant VALUE (either 0 or
   1), and is of the indicated TYPE.  */

static tree
constant_boolean_node (value, type)
     int value;
     tree type;
{
  if (type == integer_type_node)
    return value ? integer_one_node : integer_zero_node;
  else if (TREE_CODE (type) == BOOLEAN_TYPE)
    return truthvalue_conversion (value ? integer_one_node :
                          integer_zero_node); 
  else 
    {
      tree t = build_int_2 (value, 0);
      TREE_TYPE (t) = type;
      return t;
    }
}

/* Perform constant folding and related simplification of EXPR.
   The related simplifications include x*1 => x, x*0 => 0, etc.,
   and application of the associative law.
   NOP_EXPR conversions may be removed freely (as long as we
   are careful not to change the C type of the overall expression)
   We cannot simplify through a CONVERT_EXPR, FIX_EXPR or FLOAT_EXPR,
   but we can constant-fold them if they have constant operands.  */

tree
fold (expr) 
     tree expr;
{
  register tree t = expr;
  tree t1 = NULL_TREE;
  tree tem;
  tree type = TREE_TYPE (expr);
  register tree arg0 = NULL_TREE, arg1 = NULL_TREE;
  register enum tree_code code = TREE_CODE (t);
  register int kind;
  int invert;

  /* WINS will be nonzero when the switch is done
     if all operands are constant.  */

  int wins = 1;

  /* Don't try to process an RTL_EXPR since its operands aren't trees. 
     Likewise for a SAVE_EXPR that's already been evaluated.  */
  if (code == RTL_EXPR || (code == SAVE_EXPR && SAVE_EXPR_RTL (t)) != 0)
    return t;

  /* Return right away if already constant.  */
  if (TREE_CONSTANT (t))
    {
      if (code == CONST_DECL)
      return DECL_INITIAL (t);
      return t;
    }
  
#ifdef MAX_INTEGER_COMPUTATION_MODE
  check_max_integer_computation_mode (expr);
#endif

  kind = TREE_CODE_CLASS (code);
  if (code == NOP_EXPR || code == FLOAT_EXPR || code == CONVERT_EXPR)
    {
      tree subop;

      /* Special case for conversion ops that can have fixed point args.  */
      arg0 = TREE_OPERAND (t, 0);

      /* Don't use STRIP_NOPS, because signedness of argument type matters.  */
      if (arg0 != 0)
      STRIP_TYPE_NOPS (arg0);

      if (arg0 != 0 && TREE_CODE (arg0) == COMPLEX_CST)
      subop = TREE_REALPART (arg0);
      else
      subop = arg0;

      if (subop != 0 && TREE_CODE (subop) != INTEGER_CST
#if ! defined (REAL_IS_NOT_DOUBLE) || defined (REAL_ARITHMETIC)
        && TREE_CODE (subop) != REAL_CST
#endif /* not REAL_IS_NOT_DOUBLE, or REAL_ARITHMETIC */
        )
      /* Note that TREE_CONSTANT isn't enough:
         static var addresses are constant but we can't
         do arithmetic on them.  */
      wins = 0;
    }
  else if (kind == 'e' || kind == '<'
         || kind == '1' || kind == '2' || kind == 'r')
    {
      register int len = tree_code_length[(int) code];
      register int i;
      for (i = 0; i < len; i++)
      {
        tree op = TREE_OPERAND (t, i);
        tree subop;

        if (op == 0)
          continue;           /* Valid for CALL_EXPR, at least.  */

        if (kind == '<' || code == RSHIFT_EXPR)
          {
            /* Signedness matters here.  Perhaps we can refine this
             later.  */
            STRIP_TYPE_NOPS (op);
          }
        else
          {
            /* Strip any conversions that don't change the mode.  */
            STRIP_NOPS (op);
          }
        
        if (TREE_CODE (op) == COMPLEX_CST)
          subop = TREE_REALPART (op);
        else
          subop = op;

        if (TREE_CODE (subop) != INTEGER_CST
#if ! defined (REAL_IS_NOT_DOUBLE) || defined (REAL_ARITHMETIC)
            && TREE_CODE (subop) != REAL_CST
#endif /* not REAL_IS_NOT_DOUBLE, or REAL_ARITHMETIC */
            )
          /* Note that TREE_CONSTANT isn't enough:
             static var addresses are constant but we can't
             do arithmetic on them.  */
          wins = 0;

        if (i == 0)
          arg0 = op;
        else if (i == 1)
          arg1 = op;
      }
    }

  /* If this is a commutative operation, and ARG0 is a constant, move it
     to ARG1 to reduce the number of tests below.  */
  if ((code == PLUS_EXPR || code == MULT_EXPR || code == MIN_EXPR
       || code == MAX_EXPR || code == BIT_IOR_EXPR || code == BIT_XOR_EXPR
       || code == BIT_AND_EXPR)
      && (TREE_CODE (arg0) == INTEGER_CST || TREE_CODE (arg0) == REAL_CST))
    {
      tem = arg0; arg0 = arg1; arg1 = tem;

      tem = TREE_OPERAND (t, 0); TREE_OPERAND (t, 0) = TREE_OPERAND (t, 1);
      TREE_OPERAND (t, 1) = tem;
    }

  /* Now WINS is set as described above,
     ARG0 is the first operand of EXPR,
     and ARG1 is the second operand (if it has more than one operand).

     First check for cases where an arithmetic operation is applied to a
     compound, conditional, or comparison operation.  Push the arithmetic
     operation inside the compound or conditional to see if any folding
     can then be done.  Convert comparison to conditional for this purpose.
     The also optimizes non-constant cases that used to be done in
     expand_expr.

     Before we do that, see if this is a BIT_AND_EXPR or a BIT_OR_EXPR,
     one of the operands is a comparison and the other is a comparison, a
     BIT_AND_EXPR with the constant 1, or a truth value.  In that case, the
     code below would make the expression more complex.  Change it to a
     TRUTH_{AND,OR}_EXPR.  Likewise, convert a similar NE_EXPR to 
     TRUTH_XOR_EXPR and an EQ_EXPR to the inversion of a TRUTH_XOR_EXPR.  */

  if ((code == BIT_AND_EXPR || code == BIT_IOR_EXPR
       || code == EQ_EXPR || code == NE_EXPR)
      && ((truth_value_p (TREE_CODE (arg0))
         && (truth_value_p (TREE_CODE (arg1))
             || (TREE_CODE (arg1) == BIT_AND_EXPR
               && integer_onep (TREE_OPERAND (arg1, 1)))))
        || (truth_value_p (TREE_CODE (arg1))
            && (truth_value_p (TREE_CODE (arg0))
              || (TREE_CODE (arg0) == BIT_AND_EXPR
                  && integer_onep (TREE_OPERAND (arg0, 1)))))))
    {
      t = fold (build (code == BIT_AND_EXPR ? TRUTH_AND_EXPR
                   : code == BIT_IOR_EXPR ? TRUTH_OR_EXPR
                   : TRUTH_XOR_EXPR,
                   type, arg0, arg1));

      if (code == EQ_EXPR)
      t = invert_truthvalue (t);

      return t;
    }

  if (TREE_CODE_CLASS (code) == '1')
    {
      if (TREE_CODE (arg0) == COMPOUND_EXPR)
      return build (COMPOUND_EXPR, type, TREE_OPERAND (arg0, 0),
                  fold (build1 (code, type, TREE_OPERAND (arg0, 1))));
      else if (TREE_CODE (arg0) == COND_EXPR)
      {
        t = fold (build (COND_EXPR, type, TREE_OPERAND (arg0, 0),
                     fold (build1 (code, type, TREE_OPERAND (arg0, 1))),
                     fold (build1 (code, type, TREE_OPERAND (arg0, 2)))));

        /* If this was a conversion, and all we did was to move into
           inside the COND_EXPR, bring it back out.  But leave it if
           it is a conversion from integer to integer and the
           result precision is no wider than a word since such a
           conversion is cheap and may be optimized away by combine,
           while it couldn't if it were outside the COND_EXPR.  Then return
           so we don't get into an infinite recursion loop taking the
           conversion out and then back in.  */

        if ((code == NOP_EXPR || code == CONVERT_EXPR
             || code == NON_LVALUE_EXPR)
            && TREE_CODE (t) == COND_EXPR
            && TREE_CODE (TREE_OPERAND (t, 1)) == code
            && TREE_CODE (TREE_OPERAND (t, 2)) == code
            && (TREE_TYPE (TREE_OPERAND (TREE_OPERAND (t, 1), 0))
              == TREE_TYPE (TREE_OPERAND (TREE_OPERAND (t, 2), 0)))
            && ! (INTEGRAL_TYPE_P (TREE_TYPE (t))
                && INTEGRAL_TYPE_P (TREE_TYPE (TREE_OPERAND (TREE_OPERAND (t, 1), 0)))
                && TYPE_PRECISION (TREE_TYPE (t)) <= BITS_PER_WORD))
          t = build1 (code, type,
                  build (COND_EXPR,
                         TREE_TYPE (TREE_OPERAND (TREE_OPERAND (t, 1), 0)),
                         TREE_OPERAND (t, 0),
                         TREE_OPERAND (TREE_OPERAND (t, 1), 0),
                         TREE_OPERAND (TREE_OPERAND (t, 2), 0)));
        return t;
      }
      else if (TREE_CODE_CLASS (TREE_CODE (arg0)) == '<') 
      return fold (build (COND_EXPR, type, arg0,
                      fold (build1 (code, type, integer_one_node)),
                      fold (build1 (code, type, integer_zero_node))));
   }
  else if (TREE_CODE_CLASS (code) == '2'
         || TREE_CODE_CLASS (code) == '<')
    {
      if (TREE_CODE (arg1) == COMPOUND_EXPR)
      return build (COMPOUND_EXPR, type, TREE_OPERAND (arg1, 0),
                  fold (build (code, type,
                           arg0, TREE_OPERAND (arg1, 1))));
      else if ((TREE_CODE (arg1) == COND_EXPR
            || (TREE_CODE_CLASS (TREE_CODE (arg1)) == '<'
                && TREE_CODE_CLASS (code) != '<'))
             && (! TREE_SIDE_EFFECTS (arg0)
               || (current_function_decl != 0
                   && ! contains_placeholder_p (arg0))))
      {
        tree test, true_value, false_value;
        tree lhs = 0, rhs = 0;

        if (TREE_CODE (arg1) == COND_EXPR)
          {
            test = TREE_OPERAND (arg1, 0);
            true_value = TREE_OPERAND (arg1, 1);
            false_value = TREE_OPERAND (arg1, 2);
          }
        else
          {
            tree testtype = TREE_TYPE (arg1);
            test = arg1;
            true_value = convert (testtype, integer_one_node);
            false_value = convert (testtype, integer_zero_node);
          }

        /* If ARG0 is complex we want to make sure we only evaluate
           it once.  Though this is only required if it is volatile, it
           might be more efficient even if it is not.  However, if we
           succeed in folding one part to a constant, we do not need
           to make this SAVE_EXPR.  Since we do this optimization
           primarily to see if we do end up with constant and this
           SAVE_EXPR interferes with later optimizations, suppressing
           it when we can is important.

           If we are not in a function, we can't make a SAVE_EXPR, so don't
           try to do so.  Don't try to see if the result is a constant
           if an arm is a COND_EXPR since we get exponential behavior
           in that case.  */

        if (TREE_CODE (arg0) != SAVE_EXPR && ! TREE_CONSTANT (arg0)
            && current_function_decl != 0
            && ((TREE_CODE (arg0) != VAR_DECL
               && TREE_CODE (arg0) != PARM_DECL)
              || TREE_SIDE_EFFECTS (arg0)))
          {
            if (TREE_CODE (true_value) != COND_EXPR)
            lhs = fold (build (code, type, arg0, true_value));

            if (TREE_CODE (false_value) != COND_EXPR)
            rhs = fold (build (code, type, arg0, false_value));

            if ((lhs == 0 || ! TREE_CONSTANT (lhs))
              && (rhs == 0 || !TREE_CONSTANT (rhs)))
            arg0 = save_expr (arg0), lhs = rhs = 0;
          }

        if (lhs == 0)
          lhs = fold (build (code, type, arg0, true_value));
        if (rhs == 0)
          rhs = fold (build (code, type, arg0, false_value));

        test = fold (build (COND_EXPR, type, test, lhs, rhs));

        if (TREE_CODE (arg0) == SAVE_EXPR)
          return build (COMPOUND_EXPR, type,
                    convert (void_type_node, arg0),
                    strip_compound_expr (test, arg0));
        else
          return convert (type, test);
      }

      else if (TREE_CODE (arg0) == COMPOUND_EXPR)
      return build (COMPOUND_EXPR, type, TREE_OPERAND (arg0, 0),
                  fold (build (code, type, TREE_OPERAND (arg0, 1), arg1)));
      else if ((TREE_CODE (arg0) == COND_EXPR
            || (TREE_CODE_CLASS (TREE_CODE (arg0)) == '<'
                && TREE_CODE_CLASS (code) != '<'))
             && (! TREE_SIDE_EFFECTS (arg1)
               || (current_function_decl != 0
                   && ! contains_placeholder_p (arg1))))
      {
        tree test, true_value, false_value;
        tree lhs = 0, rhs = 0;

        if (TREE_CODE (arg0) == COND_EXPR)
          {
            test = TREE_OPERAND (arg0, 0);
            true_value = TREE_OPERAND (arg0, 1);
            false_value = TREE_OPERAND (arg0, 2);
          }
        else
          {
            tree testtype = TREE_TYPE (arg0);
            test = arg0;
            true_value = convert (testtype, integer_one_node);
            false_value = convert (testtype, integer_zero_node);
          }

        if (TREE_CODE (arg1) != SAVE_EXPR && ! TREE_CONSTANT (arg0)
            && current_function_decl != 0
            && ((TREE_CODE (arg1) != VAR_DECL
               && TREE_CODE (arg1) != PARM_DECL)
              || TREE_SIDE_EFFECTS (arg1)))
          {
            if (TREE_CODE (true_value) != COND_EXPR)
            lhs = fold (build (code, type, true_value, arg1));

            if (TREE_CODE (false_value) != COND_EXPR)
            rhs = fold (build (code, type, false_value, arg1));

            if ((lhs == 0 || ! TREE_CONSTANT (lhs))
              && (rhs == 0 || !TREE_CONSTANT (rhs)))
            arg1 = save_expr (arg1), lhs = rhs = 0;
          }

        if (lhs == 0)
          lhs = fold (build (code, type, true_value, arg1));

        if (rhs == 0)
          rhs = fold (build (code, type, false_value, arg1));

        test = fold (build (COND_EXPR, type, test, lhs, rhs));
        if (TREE_CODE (arg1) == SAVE_EXPR)
          return build (COMPOUND_EXPR, type,
                    convert (void_type_node, arg1),
                    strip_compound_expr (test, arg1));
        else
          return convert (type, test);
      }
    }
  else if (TREE_CODE_CLASS (code) == '<'
         && TREE_CODE (arg0) == COMPOUND_EXPR)
    return build (COMPOUND_EXPR, type, TREE_OPERAND (arg0, 0),
              fold (build (code, type, TREE_OPERAND (arg0, 1), arg1)));
  else if (TREE_CODE_CLASS (code) == '<'
         && TREE_CODE (arg1) == COMPOUND_EXPR)
    return build (COMPOUND_EXPR, type, TREE_OPERAND (arg1, 0),
              fold (build (code, type, arg0, TREE_OPERAND (arg1, 1))));
        
  switch (code)
    {
    case INTEGER_CST:
    case REAL_CST:
    case STRING_CST:
    case COMPLEX_CST:
    case CONSTRUCTOR:
      return t;

    case CONST_DECL:
      return fold (DECL_INITIAL (t));

    case NOP_EXPR:
    case FLOAT_EXPR:
    case CONVERT_EXPR:
    case FIX_TRUNC_EXPR:
      /* Other kinds of FIX are not handled properly by fold_convert.  */

      if (TREE_TYPE (TREE_OPERAND (t, 0)) == TREE_TYPE (t))
      return TREE_OPERAND (t, 0);

      /* Handle cases of two conversions in a row.  */
      if (TREE_CODE (TREE_OPERAND (t, 0)) == NOP_EXPR
        || TREE_CODE (TREE_OPERAND (t, 0)) == CONVERT_EXPR)
      {
        tree inside_type = TREE_TYPE (TREE_OPERAND (TREE_OPERAND (t, 0), 0));
        tree inter_type = TREE_TYPE (TREE_OPERAND (t, 0));
        tree final_type = TREE_TYPE (t);
        int inside_int = INTEGRAL_TYPE_P (inside_type);
        int inside_ptr = POINTER_TYPE_P (inside_type);
        int inside_float = FLOAT_TYPE_P (inside_type);
        int inside_prec = TYPE_PRECISION (inside_type);
        int inside_unsignedp = TREE_UNSIGNED (inside_type);
        int inter_int = INTEGRAL_TYPE_P (inter_type);
        int inter_ptr = POINTER_TYPE_P (inter_type);
        int inter_float = FLOAT_TYPE_P (inter_type);
        int inter_prec = TYPE_PRECISION (inter_type);
        int inter_unsignedp = TREE_UNSIGNED (inter_type);
        int final_int = INTEGRAL_TYPE_P (final_type);
        int final_ptr = POINTER_TYPE_P (final_type);
        int final_float = FLOAT_TYPE_P (final_type);
        int final_prec = TYPE_PRECISION (final_type);
        int final_unsignedp = TREE_UNSIGNED (final_type);

        /* In addition to the cases of two conversions in a row 
           handled below, if we are converting something to its own
           type via an object of identical or wider precision, neither
           conversion is needed.  */
        if (inside_type == final_type
            && ((inter_int && final_int) || (inter_float && final_float))
            && inter_prec >= final_prec)
          return TREE_OPERAND (TREE_OPERAND (t, 0), 0);

        /* Likewise, if the intermediate and final types are either both
           float or both integer, we don't need the middle conversion if
           it is wider than the final type and doesn't change the signedness
           (for integers).  Avoid this if the final type is a pointer
           since then we sometimes need the inner conversion.  Likewise if
           the outer has a precision not equal to the size of its mode.  */
        if ((((inter_int || inter_ptr) && (inside_int || inside_ptr))
             || (inter_float && inside_float))
            && inter_prec >= inside_prec
            && (inter_float || inter_unsignedp == inside_unsignedp)
            && ! (final_prec != GET_MODE_BITSIZE (TYPE_MODE (final_type))
                && TYPE_MODE (final_type) == TYPE_MODE (inter_type))
            && ! final_ptr)
          return convert (final_type, TREE_OPERAND (TREE_OPERAND (t, 0), 0));

        /* If we have a sign-extension of a zero-extended value, we can
           replace that by a single zero-extension.  */
        if (inside_int && inter_int && final_int
            && inside_prec < inter_prec && inter_prec < final_prec
            && inside_unsignedp && !inter_unsignedp)
          return convert (final_type, TREE_OPERAND (TREE_OPERAND (t, 0), 0));

        /* Two conversions in a row are not needed unless:
           - some conversion is floating-point (overstrict for now), or
           - the intermediate type is narrower than both initial and
             final, or
           - the intermediate type and innermost type differ in signedness,
             and the outermost type is wider than the intermediate, or
           - the initial type is a pointer type and the precisions of the
             intermediate and final types differ, or
           - the final type is a pointer type and the precisions of the 
             initial and intermediate types differ.  */
        if (! inside_float && ! inter_float && ! final_float
            && (inter_prec > inside_prec || inter_prec > final_prec)
            && ! (inside_int && inter_int
                && inter_unsignedp != inside_unsignedp
                && inter_prec < final_prec)
            && ((inter_unsignedp && inter_prec > inside_prec)
              == (final_unsignedp && final_prec > inter_prec))
            && ! (inside_ptr && inter_prec != final_prec)
            && ! (final_ptr && inside_prec != inter_prec)
            && ! (final_prec != GET_MODE_BITSIZE (TYPE_MODE (final_type))
                && TYPE_MODE (final_type) == TYPE_MODE (inter_type))
            && ! final_ptr)
          return convert (final_type, TREE_OPERAND (TREE_OPERAND (t, 0), 0));
      }

      if (TREE_CODE (TREE_OPERAND (t, 0)) == MODIFY_EXPR
        && TREE_CONSTANT (TREE_OPERAND (TREE_OPERAND (t, 0), 1))
        /* Detect assigning a bitfield.  */
        && !(TREE_CODE (TREE_OPERAND (TREE_OPERAND (t, 0), 0)) == COMPONENT_REF
             && DECL_BIT_FIELD (TREE_OPERAND (TREE_OPERAND (TREE_OPERAND (t, 0), 0), 1))))
      {
        /* Don't leave an assignment inside a conversion
           unless assigning a bitfield.  */
        tree prev = TREE_OPERAND (t, 0);
        TREE_OPERAND (t, 0) = TREE_OPERAND (prev, 1);
        /* First do the assignment, then return converted constant.  */
        t = build (COMPOUND_EXPR, TREE_TYPE (t), prev, fold (t));
        TREE_USED (t) = 1;
        return t;
      }
      if (!wins)
      {
        TREE_CONSTANT (t) = TREE_CONSTANT (arg0);
        return t;
      }
      return fold_convert (t, arg0);

#if 0  /* This loses on &"foo"[0].  */
    case ARRAY_REF:
      {
        int i;

        /* Fold an expression like: "foo"[2] */
        if (TREE_CODE (arg0) == STRING_CST
            && TREE_CODE (arg1) == INTEGER_CST
            && !TREE_INT_CST_HIGH (arg1)
            && (i = TREE_INT_CST_LOW (arg1)) < TREE_STRING_LENGTH (arg0))
          {
            t = build_int_2 (TREE_STRING_POINTER (arg0)[i], 0);
            TREE_TYPE (t) = TREE_TYPE (TREE_TYPE (arg0));
            force_fit_type (t, 0);
          }
      }
      return t;
#endif /* 0 */

    case COMPONENT_REF:
      if (TREE_CODE (arg0) == CONSTRUCTOR)
      {
        tree m = purpose_member (arg1, CONSTRUCTOR_ELTS (arg0));
        if (m)
          t = TREE_VALUE (m);
      }
      return t;

    case RANGE_EXPR:
      TREE_CONSTANT (t) = wins;
      return t;

    case NEGATE_EXPR:
      if (wins)
      {
        if (TREE_CODE (arg0) == INTEGER_CST)
          {
            HOST_WIDE_INT low, high;
            int overflow = neg_double (TREE_INT_CST_LOW (arg0),
                               TREE_INT_CST_HIGH (arg0),
                               &low, &high);
            t = build_int_2 (low, high);
            TREE_TYPE (t) = type;
            TREE_OVERFLOW (t)
            = (TREE_OVERFLOW (arg0)
               | force_fit_type (t, overflow && !TREE_UNSIGNED (type)));
            TREE_CONSTANT_OVERFLOW (t)
            = TREE_OVERFLOW (t) | TREE_CONSTANT_OVERFLOW (arg0);
          }
        else if (TREE_CODE (arg0) == REAL_CST)
          t = build_real (type, REAL_VALUE_NEGATE (TREE_REAL_CST (arg0)));
      }
      else if (TREE_CODE (arg0) == NEGATE_EXPR)
      return TREE_OPERAND (arg0, 0);

      /* Convert - (a - b) to (b - a) for non-floating-point.  */
      else if (TREE_CODE (arg0) == MINUS_EXPR && ! FLOAT_TYPE_P (type))
      return build (MINUS_EXPR, type, TREE_OPERAND (arg0, 1),
                  TREE_OPERAND (arg0, 0));

      return t;

    case ABS_EXPR:
      if (wins)
      {
        if (TREE_CODE (arg0) == INTEGER_CST)
          {
            if (! TREE_UNSIGNED (type)
              && TREE_INT_CST_HIGH (arg0) < 0)
            {
              HOST_WIDE_INT low, high;
              int overflow = neg_double (TREE_INT_CST_LOW (arg0),
                                   TREE_INT_CST_HIGH (arg0),
                                   &low, &high);
              t = build_int_2 (low, high);
              TREE_TYPE (t) = type;
              TREE_OVERFLOW (t)
                = (TREE_OVERFLOW (arg0)
                   | force_fit_type (t, overflow));
              TREE_CONSTANT_OVERFLOW (t)
                = TREE_OVERFLOW (t) | TREE_CONSTANT_OVERFLOW (arg0);
            }
          }
        else if (TREE_CODE (arg0) == REAL_CST)
          {
            if (REAL_VALUE_NEGATIVE (TREE_REAL_CST (arg0)))
            t = build_real (type,
                        REAL_VALUE_NEGATE (TREE_REAL_CST (arg0)));
          }
      }
      else if (TREE_CODE (arg0) == ABS_EXPR || TREE_CODE (arg0) == NEGATE_EXPR)
      return build1 (ABS_EXPR, type, TREE_OPERAND (arg0, 0));
      return t;

    case CONJ_EXPR:
      if (TREE_CODE (TREE_TYPE (arg0)) != COMPLEX_TYPE)
      return arg0;
      else if (TREE_CODE (arg0) == COMPLEX_EXPR)
      return build (COMPLEX_EXPR, TREE_TYPE (arg0),
                  TREE_OPERAND (arg0, 0),
                  fold (build1 (NEGATE_EXPR,
                            TREE_TYPE (TREE_TYPE (arg0)),
                            TREE_OPERAND (arg0, 1))));
      else if (TREE_CODE (arg0) == COMPLEX_CST)
      return build_complex (type, TREE_OPERAND (arg0, 0),
                        fold (build1 (NEGATE_EXPR,
                                  TREE_TYPE (TREE_TYPE (arg0)),
                                  TREE_OPERAND (arg0, 1))));
      else if (TREE_CODE (arg0) == PLUS_EXPR || TREE_CODE (arg0) == MINUS_EXPR)
      return fold (build (TREE_CODE (arg0), type,
                      fold (build1 (CONJ_EXPR, type,
                                TREE_OPERAND (arg0, 0))),
                      fold (build1 (CONJ_EXPR,
                                type, TREE_OPERAND (arg0, 1)))));
      else if (TREE_CODE (arg0) == CONJ_EXPR)
      return TREE_OPERAND (arg0, 0);
      return t;

    case BIT_NOT_EXPR:
      if (wins)
      {
        t = build_int_2 (~ TREE_INT_CST_LOW (arg0),
                     ~ TREE_INT_CST_HIGH (arg0));
        TREE_TYPE (t) = type;
        force_fit_type (t, 0);
        TREE_OVERFLOW (t) = TREE_OVERFLOW (arg0);
        TREE_CONSTANT_OVERFLOW (t) = TREE_CONSTANT_OVERFLOW (arg0);
      }
      else if (TREE_CODE (arg0) == BIT_NOT_EXPR)
      return TREE_OPERAND (arg0, 0);
      return t;

    case PLUS_EXPR:
      /* A + (-B) -> A - B */
      if (TREE_CODE (arg1) == NEGATE_EXPR)
      return fold (build (MINUS_EXPR, type, arg0, TREE_OPERAND (arg1, 0)));
      else if (! FLOAT_TYPE_P (type))
      {
        if (integer_zerop (arg1))
          return non_lvalue (convert (type, arg0));

        /* If we are adding two BIT_AND_EXPR's, both of which are and'ing
           with a constant, and the two constants have no bits in common,
           we should treat this as a BIT_IOR_EXPR since this may produce more
           simplifications.  */
        if (TREE_CODE (arg0) == BIT_AND_EXPR
            && TREE_CODE (arg1) == BIT_AND_EXPR
            && TREE_CODE (TREE_OPERAND (arg0, 1)) == INTEGER_CST
            && TREE_CODE (TREE_OPERAND (arg1, 1)) == INTEGER_CST
            && integer_zerop (const_binop (BIT_AND_EXPR,
                                   TREE_OPERAND (arg0, 1),
                                   TREE_OPERAND (arg1, 1), 0)))
          {
            code = BIT_IOR_EXPR;
            goto bit_ior;
          }

        /* (A * C) + (B * C) -> (A+B) * C.  Since we are most concerned
           about the case where C is a constant, just try one of the
           four possibilities.  */

        if (TREE_CODE (arg0) == MULT_EXPR && TREE_CODE (arg1) == MULT_EXPR
            && operand_equal_p (TREE_OPERAND (arg0, 1),
                          TREE_OPERAND (arg1, 1), 0))
          return fold (build (MULT_EXPR, type,
                        fold (build (PLUS_EXPR, type,
                                   TREE_OPERAND (arg0, 0),
                                   TREE_OPERAND (arg1, 0))),
                        TREE_OPERAND (arg0, 1)));
      }
      /* In IEEE floating point, x+0 may not equal x.  */
      else if ((TARGET_FLOAT_FORMAT != IEEE_FLOAT_FORMAT
            || flag_fast_math)
             && real_zerop (arg1))
      return non_lvalue (convert (type, arg0));
    associate:
      /* In most languages, can't associate operations on floats
       through parentheses.  Rather than remember where the parentheses
       were, we don't associate floats at all.  It shouldn't matter much.
       However, associating multiplications is only very slightly
       inaccurate, so do that if -ffast-math is specified.  */
      if (FLOAT_TYPE_P (type)
        && ! (flag_fast_math && code == MULT_EXPR))
      goto binary;

      /* The varsign == -1 cases happen only for addition and subtraction.
       It says that the arg that was split was really CON minus VAR.
       The rest of the code applies to all associative operations.  */
      if (!wins)
      {
        tree var, con;
        int varsign;

        if (split_tree (arg0, code, &var, &con, &varsign))
          {
            if (varsign == -1)
            {
              /* EXPR is (CON-VAR) +- ARG1.  */
              /* If it is + and VAR==ARG1, return just CONST.  */
              if (code == PLUS_EXPR && operand_equal_p (var, arg1, 0))
                return convert (TREE_TYPE (t), con);
                
              /* If ARG0 is a constant, don't change things around;
                 instead keep all the constant computations together.  */

              if (TREE_CONSTANT (arg0))
                return t;

              /* Otherwise return (CON +- ARG1) - VAR.  */
              t = build (MINUS_EXPR, type,
                       fold (build (code, type, con, arg1)), var);
            }
            else
            {
              /* EXPR is (VAR+CON) +- ARG1.  */
              /* If it is - and VAR==ARG1, return just CONST.  */
              if (code == MINUS_EXPR && operand_equal_p (var, arg1, 0))
                return convert (TREE_TYPE (t), con);
                
              /* If ARG0 is a constant, don't change things around;
                 instead keep all the constant computations together.  */

              if (TREE_CONSTANT (arg0))
                return t;

              /* Otherwise return VAR +- (ARG1 +- CON).  */
              tem = fold (build (code, type, arg1, con));
              t = build (code, type, var, tem);

              if (integer_zerop (tem)
                  && (code == PLUS_EXPR || code == MINUS_EXPR))
                return convert (type, var);
              /* If we have x +/- (c - d) [c an explicit integer]
                 change it to x -/+ (d - c) since if d is relocatable
                 then the latter can be a single immediate insn
                 and the former cannot.  */
              if (TREE_CODE (tem) == MINUS_EXPR
                  && TREE_CODE (TREE_OPERAND (tem, 0)) == INTEGER_CST)
                {
                  tree tem1 = TREE_OPERAND (tem, 1);
                  TREE_OPERAND (tem, 1) = TREE_OPERAND (tem, 0);
                  TREE_OPERAND (tem, 0) = tem1;
                  TREE_SET_CODE (t,
                             (code == PLUS_EXPR ? MINUS_EXPR : PLUS_EXPR));
                }
            }
            return t;
          }

        if (split_tree (arg1, code, &var, &con, &varsign))
          {
            if (TREE_CONSTANT (arg1))
            return t;

            if (varsign == -1)
            TREE_SET_CODE (t,
                         (code == PLUS_EXPR ? MINUS_EXPR : PLUS_EXPR));

            /* EXPR is ARG0 +- (CON +- VAR).  */
            if (TREE_CODE (t) == MINUS_EXPR
              && operand_equal_p (var, arg0, 0))
            {
              /* If VAR and ARG0 cancel, return just CON or -CON.  */
              if (code == PLUS_EXPR)
                return convert (TREE_TYPE (t), con);
              return fold (build1 (NEGATE_EXPR, TREE_TYPE (t),
                               convert (TREE_TYPE (t), con)));
            }

            t = build (TREE_CODE (t), type,
                   fold (build (code, TREE_TYPE (t), arg0, con)), var);

            if (integer_zerop (TREE_OPERAND (t, 0))
              && TREE_CODE (t) == PLUS_EXPR)
            return convert (TREE_TYPE (t), var);
            return t;
          }
      }
    binary:
#if defined (REAL_IS_NOT_DOUBLE) && ! defined (REAL_ARITHMETIC)
      if (TREE_CODE (arg1) == REAL_CST)
      return t;
#endif /* REAL_IS_NOT_DOUBLE, and no REAL_ARITHMETIC */
      if (wins)
      t1 = const_binop (code, arg0, arg1, 0);
      if (t1 != NULL_TREE)
      {
        /* The return value should always have
           the same type as the original expression.  */
        if (TREE_TYPE (t1) != TREE_TYPE (t))
          t1 = convert (TREE_TYPE (t), t1);

        return t1;
      }
      return t;

    case MINUS_EXPR:
      if (! FLOAT_TYPE_P (type))
      {
        if (! wins && integer_zerop (arg0))
          return build1 (NEGATE_EXPR, type, arg1);
        if (integer_zerop (arg1))
          return non_lvalue (convert (type, arg0));

        /* (A * C) - (B * C) -> (A-B) * C.  Since we are most concerned
           about the case where C is a constant, just try one of the
           four possibilities.  */

        if (TREE_CODE (arg0) == MULT_EXPR && TREE_CODE (arg1) == MULT_EXPR
            && operand_equal_p (TREE_OPERAND (arg0, 1),
                          TREE_OPERAND (arg1, 1), 0))
          return fold (build (MULT_EXPR, type,
                        fold (build (MINUS_EXPR, type,
                                   TREE_OPERAND (arg0, 0),
                                   TREE_OPERAND (arg1, 0))),
                        TREE_OPERAND (arg0, 1)));
      }
      /* Convert A - (-B) to A + B.  */
      else if (TREE_CODE (arg1) == NEGATE_EXPR)
      return fold (build (PLUS_EXPR, type, arg0, TREE_OPERAND (arg1, 0)));

      else if (TARGET_FLOAT_FORMAT != IEEE_FLOAT_FORMAT
             || flag_fast_math)
      {
        /* Except with IEEE floating point, 0-x equals -x.  */
        if (! wins && real_zerop (arg0))
          return build1 (NEGATE_EXPR, type, arg1);
        /* Except with IEEE floating point, x-0 equals x.  */
        if (real_zerop (arg1))
          return non_lvalue (convert (type, arg0));
      }

      /* Fold &x - &x.  This can happen from &x.foo - &x. 
       This is unsafe for certain floats even in non-IEEE formats.
       In IEEE, it is unsafe because it does wrong for NaNs.
       Also note that operand_equal_p is always false if an operand
       is volatile.  */

      if ((! FLOAT_TYPE_P (type) || flag_fast_math)
        && operand_equal_p (arg0, arg1, 0))
      return convert (type, integer_zero_node);

      goto associate;

    case MULT_EXPR:
      if (! FLOAT_TYPE_P (type))
      {
        if (integer_zerop (arg1))
          return omit_one_operand (type, arg1, arg0);
        if (integer_onep (arg1))
          return non_lvalue (convert (type, arg0));

        /* ((A / C) * C) is A if the division is an
           EXACT_DIV_EXPR.   Since C is normally a constant,
           just check for one of the four possibilities.  */

        if (TREE_CODE (arg0) == EXACT_DIV_EXPR
            && operand_equal_p (TREE_OPERAND (arg0, 1), arg1, 0))
          return TREE_OPERAND (arg0, 0);

        /* (a * (1 << b)) is (a << b)  */
        if (TREE_CODE (arg1) == LSHIFT_EXPR
            && integer_onep (TREE_OPERAND (arg1, 0)))
          return fold (build (LSHIFT_EXPR, type, arg0,
                        TREE_OPERAND (arg1, 1)));
        if (TREE_CODE (arg0) == LSHIFT_EXPR
            && integer_onep (TREE_OPERAND (arg0, 0)))
          return fold (build (LSHIFT_EXPR, type, arg1,
                        TREE_OPERAND (arg0, 1)));
      }
      else
      {
        /* x*0 is 0, except for IEEE floating point.  */
        if ((TARGET_FLOAT_FORMAT != IEEE_FLOAT_FORMAT
             || flag_fast_math)
            && real_zerop (arg1))
          return omit_one_operand (type, arg1, arg0);
        /* In IEEE floating point, x*1 is not equivalent to x for snans.
           However, ANSI says we can drop signals,
           so we can do this anyway.  */
        if (real_onep (arg1))
          return non_lvalue (convert (type, arg0));
        /* x*2 is x+x */
        if (! wins && real_twop (arg1) && current_function_decl != 0
            && ! contains_placeholder_p (arg0))
          {
            tree arg = save_expr (arg0);
            return build (PLUS_EXPR, type, arg, arg);
          }
      }
      goto associate;

    case BIT_IOR_EXPR:
    bit_ior:
      {
      register enum tree_code code0, code1;

      if (integer_all_onesp (arg1))
      return omit_one_operand (type, arg1, arg0);
      if (integer_zerop (arg1))
      return non_lvalue (convert (type, arg0));
      t1 = distribute_bit_expr (code, type, arg0, arg1);
      if (t1 != NULL_TREE)
      return t1;

      /* (A << C1) | (A >> C2) if A is unsigned and C1+C2 is the size of A
       is a rotate of A by C1 bits.  */
      /* (A << B) | (A >> (Z - B)) if A is unsigned and Z is the size of A
       is a rotate of A by B bits.  */

      code0 = TREE_CODE (arg0);
      code1 = TREE_CODE (arg1);
      if (((code0 == RSHIFT_EXPR && code1 == LSHIFT_EXPR)
        || (code1 == RSHIFT_EXPR && code0 == LSHIFT_EXPR))
        && operand_equal_p (TREE_OPERAND (arg0, 0), TREE_OPERAND (arg1,0), 0)
        && TREE_UNSIGNED (TREE_TYPE (TREE_OPERAND (arg0, 0))))
      {
        register tree tree01, tree11;
        register enum tree_code code01, code11;

        tree01 = TREE_OPERAND (arg0, 1);
        tree11 = TREE_OPERAND (arg1, 1);
        code01 = TREE_CODE (tree01);
        code11 = TREE_CODE (tree11);
        if (code01 == INTEGER_CST
          && code11 == INTEGER_CST
          && TREE_INT_CST_HIGH (tree01) == 0
          && TREE_INT_CST_HIGH (tree11) == 0
          && ((TREE_INT_CST_LOW (tree01) + TREE_INT_CST_LOW (tree11))
            == TYPE_PRECISION (TREE_TYPE (TREE_OPERAND (arg0, 0)))))
          return build (LROTATE_EXPR, type, TREE_OPERAND (arg0, 0),
                  code0 == LSHIFT_EXPR ? tree01 : tree11);
        else if (code11 == MINUS_EXPR
            && TREE_CODE (TREE_OPERAND (tree11, 0)) == INTEGER_CST
            && TREE_INT_CST_HIGH (TREE_OPERAND (tree11, 0)) == 0
            && TREE_INT_CST_LOW (TREE_OPERAND (tree11, 0))
              == TYPE_PRECISION (TREE_TYPE (TREE_OPERAND (arg0, 0)))
            && operand_equal_p (tree01, TREE_OPERAND (tree11, 1), 0))
          return build (code0 == LSHIFT_EXPR ? LROTATE_EXPR : RROTATE_EXPR,
                  type, TREE_OPERAND (arg0, 0), tree01);
        else if (code01 == MINUS_EXPR
            && TREE_CODE (TREE_OPERAND (tree01, 0)) == INTEGER_CST
            && TREE_INT_CST_HIGH (TREE_OPERAND (tree01, 0)) == 0
            && TREE_INT_CST_LOW (TREE_OPERAND (tree01, 0))
              == TYPE_PRECISION (TREE_TYPE (TREE_OPERAND (arg0, 0)))
            && operand_equal_p (tree11, TREE_OPERAND (tree01, 1), 0))
          return build (code0 != LSHIFT_EXPR ? LROTATE_EXPR : RROTATE_EXPR,
                  type, TREE_OPERAND (arg0, 0), tree11);
      }

      goto associate;
      }

    case BIT_XOR_EXPR:
      if (integer_zerop (arg1))
      return non_lvalue (convert (type, arg0));
      if (integer_all_onesp (arg1))
      return fold (build1 (BIT_NOT_EXPR, type, arg0));
      goto associate;

    case BIT_AND_EXPR:
    bit_and:
      if (integer_all_onesp (arg1))
      return non_lvalue (convert (type, arg0));
      if (integer_zerop (arg1))
      return omit_one_operand (type, arg1, arg0);
      t1 = distribute_bit_expr (code, type, arg0, arg1);
      if (t1 != NULL_TREE)
      return t1;
      /* Simplify ((int)c & 0x377) into (int)c, if c is unsigned char.  */
      if (TREE_CODE (arg0) == INTEGER_CST && TREE_CODE (arg1) == NOP_EXPR
        && TREE_UNSIGNED (TREE_TYPE (TREE_OPERAND (arg1, 0))))
      {
        int prec = TYPE_PRECISION (TREE_TYPE (TREE_OPERAND (arg1, 0)));
        if (prec < BITS_PER_WORD && prec < HOST_BITS_PER_WIDE_INT
            && (~TREE_INT_CST_LOW (arg0)
              & (((HOST_WIDE_INT) 1 << prec) - 1)) == 0)
          return build1 (NOP_EXPR, type, TREE_OPERAND (arg1, 0));
      }
      if (TREE_CODE (arg1) == INTEGER_CST && TREE_CODE (arg0) == NOP_EXPR
        && TREE_UNSIGNED (TREE_TYPE (TREE_OPERAND (arg0, 0))))
      {
        int prec = TYPE_PRECISION (TREE_TYPE (TREE_OPERAND (arg0, 0)));
        if (prec < BITS_PER_WORD && prec < HOST_BITS_PER_WIDE_INT
            && (~TREE_INT_CST_LOW (arg1)
              & (((HOST_WIDE_INT) 1 << prec) - 1)) == 0)
          return build1 (NOP_EXPR, type, TREE_OPERAND (arg0, 0));
      }
      goto associate;

    case BIT_ANDTC_EXPR:
      if (integer_all_onesp (arg0))
      return non_lvalue (convert (type, arg1));
      if (integer_zerop (arg0))
      return omit_one_operand (type, arg0, arg1);
      if (TREE_CODE (arg1) == INTEGER_CST)
      {
        arg1 = fold (build1 (BIT_NOT_EXPR, type, arg1));
        code = BIT_AND_EXPR;
        goto bit_and;
      }
      goto binary;

    case RDIV_EXPR:
      /* In most cases, do nothing with a divide by zero.  */
#if !defined (REAL_IS_NOT_DOUBLE) || defined (REAL_ARITHMETIC)
#ifndef REAL_INFINITY
      if (TREE_CODE (arg1) == REAL_CST && real_zerop (arg1))
      return t;
#endif
#endif /* not REAL_IS_NOT_DOUBLE, or REAL_ARITHMETIC */

      /* In IEEE floating point, x/1 is not equivalent to x for snans.
       However, ANSI says we can drop signals, so we can do this anyway.  */
      if (real_onep (arg1))
      return non_lvalue (convert (type, arg0));

      /* If ARG1 is a constant, we can convert this to a multiply by the
       reciprocal.  This does not have the same rounding properties,
       so only do this if -ffast-math.  We can actually always safely
       do it if ARG1 is a power of two, but it's hard to tell if it is
       or not in a portable manner.  */
      if (TREE_CODE (arg1) == REAL_CST)
      {
        if (flag_fast_math
            && 0 != (tem = const_binop (code, build_real (type, dconst1),
                                arg1, 0)))
          return fold (build (MULT_EXPR, type, arg0, tem));
        /* Find the reciprocal if optimizing and the result is exact. */
        else if (optimize)
          {
            REAL_VALUE_TYPE r;
            r = TREE_REAL_CST (arg1);
            if (exact_real_inverse (TYPE_MODE(TREE_TYPE(arg0)), &r))
              {
                tem = build_real (type, r);
                return fold (build (MULT_EXPR, type, arg0, tem));
              }
          }
      }
      goto binary;

    case TRUNC_DIV_EXPR:
    case ROUND_DIV_EXPR:
    case FLOOR_DIV_EXPR:
    case CEIL_DIV_EXPR:
    case EXACT_DIV_EXPR:
      if (integer_onep (arg1))
      return non_lvalue (convert (type, arg0));
      if (integer_zerop (arg1))
      return t;

      /* If arg0 is a multiple of arg1, then rewrite to the fastest div
       operation, EXACT_DIV_EXPR.

       Note that only CEIL_DIV_EXPR and FLOOR_DIV_EXPR are rewritten now.
       At one time others generated faster code, it's not clear if they do
       after the last round to changes to the DIV code in expmed.c.  */
      if ((code == CEIL_DIV_EXPR || code == FLOOR_DIV_EXPR)
        && multiple_of_p (type, arg0, arg1))
      return fold (build (EXACT_DIV_EXPR, type, arg0, arg1));

      /* If we have ((a / C1) / C2) where both division are the same type, try
       to simplify.  First see if C1 * C2 overflows or not.  */
      if (TREE_CODE (arg0) == code && TREE_CODE (arg1) == INTEGER_CST
        && TREE_CODE (TREE_OPERAND (arg0, 1)) == INTEGER_CST)
      {
        tree new_divisor;

        new_divisor = const_binop (MULT_EXPR, TREE_OPERAND (arg0, 1), arg1, 0);
        tem = const_binop (FLOOR_DIV_EXPR, new_divisor, arg1, 0);

        if (TREE_INT_CST_LOW (TREE_OPERAND (arg0, 1)) == TREE_INT_CST_LOW (tem)
            && TREE_INT_CST_HIGH (TREE_OPERAND (arg0, 1)) == TREE_INT_CST_HIGH (tem))
          {
            /* If no overflow, divide by C1*C2.  */
            return fold (build (code, type, TREE_OPERAND (arg0, 0), new_divisor));
          }
      }

      /* Look for ((a * C1) / C3) or (((a * C1) + C2) / C3),
       where C1 % C3 == 0 or C3 % C1 == 0.  We can simplify these
       expressions, which often appear in the offsets or sizes of
       objects with a varying size.  Only deal with positive divisors
       and multiplicands.   If C2 is negative, we must have C2 % C3 == 0.

       Look for NOPs and SAVE_EXPRs inside.  */

      if (TREE_CODE (arg1) == INTEGER_CST
        && tree_int_cst_sgn (arg1) >= 0)
      {
        int have_save_expr = 0;
        tree c2 = integer_zero_node;
        tree xarg0 = arg0;

        if (TREE_CODE (xarg0) == SAVE_EXPR && SAVE_EXPR_RTL (xarg0) == 0)
          have_save_expr = 1, xarg0 = TREE_OPERAND (xarg0, 0);

        STRIP_NOPS (xarg0);

        /* Look inside the dividend and simplify using EXACT_DIV_EXPR
           if possible.  */
        if (TREE_CODE (xarg0) == MULT_EXPR
            && multiple_of_p (type, TREE_OPERAND (xarg0, 0), arg1))
          {
            tree t;

            t = fold (build (MULT_EXPR, type,
                         fold (build (EXACT_DIV_EXPR, type,
                                  TREE_OPERAND (xarg0, 0), arg1)),
                         TREE_OPERAND (xarg0, 1)));
            if (have_save_expr)
            t = save_expr (t);
            return t;

          }

        if (TREE_CODE (xarg0) == MULT_EXPR
            && multiple_of_p (type, TREE_OPERAND (xarg0, 1), arg1))
          {
            tree t;

            t = fold (build (MULT_EXPR, type,
                         fold (build (EXACT_DIV_EXPR, type,
                                  TREE_OPERAND (xarg0, 1), arg1)),
                         TREE_OPERAND (xarg0, 0)));
            if (have_save_expr)
            t = save_expr (t);
            return t;
          }

        if (TREE_CODE (xarg0) == PLUS_EXPR
            && TREE_CODE (TREE_OPERAND (xarg0, 1)) == INTEGER_CST)
          c2 = TREE_OPERAND (xarg0, 1), xarg0 = TREE_OPERAND (xarg0, 0);
        else if (TREE_CODE (xarg0) == MINUS_EXPR
               && TREE_CODE (TREE_OPERAND (xarg0, 1)) == INTEGER_CST
               /* If we are doing this computation unsigned, the negate
                  is incorrect.  */
               && ! TREE_UNSIGNED (type))
          {
            c2 = fold (build1 (NEGATE_EXPR, type, TREE_OPERAND (xarg0, 1)));
            xarg0 = TREE_OPERAND (xarg0, 0);
          }

        if (TREE_CODE (xarg0) == SAVE_EXPR && SAVE_EXPR_RTL (xarg0) == 0)
          have_save_expr = 1, xarg0 = TREE_OPERAND (xarg0, 0);

        STRIP_NOPS (xarg0);

        if (TREE_CODE (xarg0) == MULT_EXPR
            && TREE_CODE (TREE_OPERAND (xarg0, 1)) == INTEGER_CST
            && tree_int_cst_sgn (TREE_OPERAND (xarg0, 1)) >= 0
            && (integer_zerop (const_binop (TRUNC_MOD_EXPR,
                                    TREE_OPERAND (xarg0, 1), arg1, 1))
              || integer_zerop (const_binop (TRUNC_MOD_EXPR, arg1,
                                     TREE_OPERAND (xarg0, 1), 1)))
            && (tree_int_cst_sgn (c2) >= 0
              || integer_zerop (const_binop (TRUNC_MOD_EXPR, c2,
                                     arg1, 1))))
          {
            tree outer_div = integer_one_node;
            tree c1 = TREE_OPERAND (xarg0, 1);
            tree c3 = arg1;

            /* If C3 > C1, set them equal and do a divide by
             C3/C1 at the end of the operation.  */
            if (tree_int_cst_lt (c1, c3))
            outer_div = const_binop (code, c3, c1, 0), c3 = c1;
            
            /* The result is A * (C1/C3) + (C2/C3).  */
            t = fold (build (PLUS_EXPR, type,
                         fold (build (MULT_EXPR, type,
                                  TREE_OPERAND (xarg0, 0),
                                  const_binop (code, c1, c3, 1))),
                         const_binop (code, c2, c3, 1)));

            if (! integer_onep (outer_div))
            t = fold (build (code, type, t, convert (type, outer_div)));

            if (have_save_expr)
            t = save_expr (t);

            return t;
          }
      }

      goto binary;

    case CEIL_MOD_EXPR:
    case FLOOR_MOD_EXPR:
    case ROUND_MOD_EXPR:
    case TRUNC_MOD_EXPR:
      if (integer_onep (arg1))
      return omit_one_operand (type, integer_zero_node, arg0);
      if (integer_zerop (arg1))
      return t;

      /* Look for ((a * C1) % C3) or (((a * C1) + C2) % C3),
       where C1 % C3 == 0.  Handle similarly to the division case,
       but don't bother with SAVE_EXPRs.  */

      if (TREE_CODE (arg1) == INTEGER_CST
        && ! integer_zerop (arg1))
      {
        tree c2 = integer_zero_node;
        tree xarg0 = arg0;

        if (TREE_CODE (xarg0) == PLUS_EXPR
            && TREE_CODE (TREE_OPERAND (xarg0, 1)) == INTEGER_CST)
          c2 = TREE_OPERAND (xarg0, 1), xarg0 = TREE_OPERAND (xarg0, 0);
        else if (TREE_CODE (xarg0) == MINUS_EXPR
               && TREE_CODE (TREE_OPERAND (xarg0, 1)) == INTEGER_CST
               && ! TREE_UNSIGNED (type))
          {
            c2 = fold (build1 (NEGATE_EXPR, type, TREE_OPERAND (xarg0, 1)));
            xarg0 = TREE_OPERAND (xarg0, 0);
          }

        STRIP_NOPS (xarg0);

        if (TREE_CODE (xarg0) == MULT_EXPR
            && TREE_CODE (TREE_OPERAND (xarg0, 1)) == INTEGER_CST
            && integer_zerop (const_binop (TRUNC_MOD_EXPR,
                                   TREE_OPERAND (xarg0, 1),
                                   arg1, 1))
            && tree_int_cst_sgn (c2) >= 0)
          /* The result is (C2%C3).  */
          return omit_one_operand (type, const_binop (code, c2, arg1, 1),
                             TREE_OPERAND (xarg0, 0));
      }

      goto binary;

    case LSHIFT_EXPR:
    case RSHIFT_EXPR:
    case LROTATE_EXPR:
    case RROTATE_EXPR:
      if (integer_zerop (arg1))
      return non_lvalue (convert (type, arg0));
      /* Since negative shift count is not well-defined,
       don't try to compute it in the compiler.  */
      if (TREE_CODE (arg1) == INTEGER_CST && tree_int_cst_sgn (arg1) < 0)
      return t;
      /* Rewrite an LROTATE_EXPR by a constant into an
       RROTATE_EXPR by a new constant.  */
      if (code == LROTATE_EXPR && TREE_CODE (arg1) == INTEGER_CST)
      {
        TREE_SET_CODE (t, RROTATE_EXPR);
        code = RROTATE_EXPR;
        TREE_OPERAND (t, 1) = arg1
          = const_binop
            (MINUS_EXPR,
             convert (TREE_TYPE (arg1),
                  build_int_2 (GET_MODE_BITSIZE (TYPE_MODE (type)), 0)),
             arg1, 0);
        if (tree_int_cst_sgn (arg1) < 0)
          return t;
      }

      /* If we have a rotate of a bit operation with the rotate count and
       the second operand of the bit operation both constant,
       permute the two operations.  */
      if (code == RROTATE_EXPR && TREE_CODE (arg1) == INTEGER_CST
        && (TREE_CODE (arg0) == BIT_AND_EXPR
            || TREE_CODE (arg0) == BIT_ANDTC_EXPR
            || TREE_CODE (arg0) == BIT_IOR_EXPR
            || TREE_CODE (arg0) == BIT_XOR_EXPR)
        && TREE_CODE (TREE_OPERAND (arg0, 1)) == INTEGER_CST)
      return fold (build (TREE_CODE (arg0), type,
                      fold (build (code, type,
                               TREE_OPERAND (arg0, 0), arg1)),
                      fold (build (code, type,
                               TREE_OPERAND (arg0, 1), arg1))));

      /* Two consecutive rotates adding up to the width of the mode can
       be ignored.  */
      if (code == RROTATE_EXPR && TREE_CODE (arg1) == INTEGER_CST
        && TREE_CODE (arg0) == RROTATE_EXPR
        && TREE_CODE (TREE_OPERAND (arg0, 1)) == INTEGER_CST
        && TREE_INT_CST_HIGH (arg1) == 0
        && TREE_INT_CST_HIGH (TREE_OPERAND (arg0, 1)) == 0
        && ((TREE_INT_CST_LOW (arg1)
             + TREE_INT_CST_LOW (TREE_OPERAND (arg0, 1)))
            == GET_MODE_BITSIZE (TYPE_MODE (type))))
      return TREE_OPERAND (arg0, 0);

      goto binary;

    case MIN_EXPR:
      if (operand_equal_p (arg0, arg1, 0))
      return arg0;
      if (INTEGRAL_TYPE_P (type)
        && operand_equal_p (arg1, TYPE_MIN_VALUE (type), 1))
      return omit_one_operand (type, arg1, arg0);
      goto associate;

    case MAX_EXPR:
      if (operand_equal_p (arg0, arg1, 0))
      return arg0;
      if (INTEGRAL_TYPE_P (type)
        && TYPE_MAX_VALUE (type)
        && operand_equal_p (arg1, TYPE_MAX_VALUE (type), 1))
      return omit_one_operand (type, arg1, arg0);
      goto associate;

    case TRUTH_NOT_EXPR:
      /* Note that the operand of this must be an int
       and its values must be 0 or 1.
       ("true" is a fixed value perhaps depending on the language,
       but we don't handle values other than 1 correctly yet.)  */
      tem = invert_truthvalue (arg0);
      /* Avoid infinite recursion.  */
      if (TREE_CODE (tem) == TRUTH_NOT_EXPR)
      return t;
      return convert (type, tem);

    case TRUTH_ANDIF_EXPR:
      /* Note that the operands of this must be ints
       and their values must be 0 or 1.
       ("true" is a fixed value perhaps depending on the language.)  */
      /* If first arg is constant zero, return it.  */
      if (integer_zerop (arg0))
      return arg0;
    case TRUTH_AND_EXPR:
      /* If either arg is constant true, drop it.  */
      if (TREE_CODE (arg0) == INTEGER_CST && ! integer_zerop (arg0))
      return non_lvalue (arg1);
      if (TREE_CODE (arg1) == INTEGER_CST && ! integer_zerop (arg1))
      return non_lvalue (arg0);
      /* If second arg is constant zero, result is zero, but first arg
       must be evaluated.  */
      if (integer_zerop (arg1))
      return omit_one_operand (type, arg1, arg0);
      /* Likewise for first arg, but note that only the TRUTH_AND_EXPR
       case will be handled here.  */
      if (integer_zerop (arg0))
      return omit_one_operand (type, arg0, arg1);

    truth_andor:
      /* We only do these simplifications if we are optimizing.  */
      if (!optimize)
      return t;

      /* Check for things like (A || B) && (A || C).  We can convert this
       to A || (B && C).  Note that either operator can be any of the four
       truth and/or operations and the transformation will still be
       valid.   Also note that we only care about order for the
       ANDIF and ORIF operators.  If B contains side effects, this
       might change the truth-value of A. */
      if (TREE_CODE (arg0) == TREE_CODE (arg1)
        && (TREE_CODE (arg0) == TRUTH_ANDIF_EXPR
            || TREE_CODE (arg0) == TRUTH_ORIF_EXPR
            || TREE_CODE (arg0) == TRUTH_AND_EXPR
            || TREE_CODE (arg0) == TRUTH_OR_EXPR)
        && ! TREE_SIDE_EFFECTS (TREE_OPERAND (arg0, 1)))
      {
        tree a00 = TREE_OPERAND (arg0, 0);
        tree a01 = TREE_OPERAND (arg0, 1);
        tree a10 = TREE_OPERAND (arg1, 0);
        tree a11 = TREE_OPERAND (arg1, 1);
        int commutative = ((TREE_CODE (arg0) == TRUTH_OR_EXPR
                        || TREE_CODE (arg0) == TRUTH_AND_EXPR)
                       && (code == TRUTH_AND_EXPR
                         || code == TRUTH_OR_EXPR));

        if (operand_equal_p (a00, a10, 0))
          return fold (build (TREE_CODE (arg0), type, a00,
                        fold (build (code, type, a01, a11))));
        else if (commutative && operand_equal_p (a00, a11, 0))
          return fold (build (TREE_CODE (arg0), type, a00,
                        fold (build (code, type, a01, a10))));
        else if (commutative && operand_equal_p (a01, a10, 0))
          return fold (build (TREE_CODE (arg0), type, a01,
                        fold (build (code, type, a00, a11))));

        /* This case if tricky because we must either have commutative
           operators or else A10 must not have side-effects.  */

        else if ((commutative || ! TREE_SIDE_EFFECTS (a10))
               && operand_equal_p (a01, a11, 0))
          return fold (build (TREE_CODE (arg0), type,
                        fold (build (code, type, a00, a10)),
                        a01));
      }

      /* See if we can build a range comparison.  */
      if (0 != (tem = fold_range_test (t)))
      return tem;

      /* Check for the possibility of merging component references.  If our
       lhs is another similar operation, try to merge its rhs with our
       rhs.  Then try to merge our lhs and rhs.  */
      if (TREE_CODE (arg0) == code
        && 0 != (tem = fold_truthop (code, type,
                               TREE_OPERAND (arg0, 1), arg1)))
      return fold (build (code, type, TREE_OPERAND (arg0, 0), tem));

      if ((tem = fold_truthop (code, type, arg0, arg1)) != 0)
      return tem;

      return t;

    case TRUTH_ORIF_EXPR:
      /* Note that the operands of this must be ints
       and their values must be 0 or true.
       ("true" is a fixed value perhaps depending on the language.)  */
      /* If first arg is constant true, return it.  */
      if (TREE_CODE (arg0) == INTEGER_CST && ! integer_zerop (arg0))
      return arg0;
    case TRUTH_OR_EXPR:
      /* If either arg is constant zero, drop it.  */
      if (TREE_CODE (arg0) == INTEGER_CST && integer_zerop (arg0))
      return non_lvalue (arg1);
      if (TREE_CODE (arg1) == INTEGER_CST && integer_zerop (arg1))
      return non_lvalue (arg0);
      /* If second arg is constant true, result is true, but we must
       evaluate first arg.  */
      if (TREE_CODE (arg1) == INTEGER_CST && ! integer_zerop (arg1))
      return omit_one_operand (type, arg1, arg0);
      /* Likewise for first arg, but note this only occurs here for
       TRUTH_OR_EXPR.  */
      if (TREE_CODE (arg0) == INTEGER_CST && ! integer_zerop (arg0))
      return omit_one_operand (type, arg0, arg1);
      goto truth_andor;

    case TRUTH_XOR_EXPR:
      /* If either arg is constant zero, drop it.  */
      if (integer_zerop (arg0))
      return non_lvalue (arg1);
      if (integer_zerop (arg1))
      return non_lvalue (arg0);
      /* If either arg is constant true, this is a logical inversion.  */
      if (integer_onep (arg0))
      return non_lvalue (invert_truthvalue (arg1));
      if (integer_onep (arg1))
      return non_lvalue (invert_truthvalue (arg0));
      return t;

    case EQ_EXPR:
    case NE_EXPR:
    case LT_EXPR:
    case GT_EXPR:
    case LE_EXPR:
    case GE_EXPR:
      /* If one arg is a constant integer, put it last.  */
      if (TREE_CODE (arg0) == INTEGER_CST
        && TREE_CODE (arg1) != INTEGER_CST)
      {
        TREE_OPERAND (t, 0) = arg1;
        TREE_OPERAND (t, 1) = arg0;
        arg0 = TREE_OPERAND (t, 0);
        arg1 = TREE_OPERAND (t, 1);
        code = swap_tree_comparison (code);
        TREE_SET_CODE (t, code);
      }

      /* Convert foo++ == CONST into ++foo == CONST + INCR.
       First, see if one arg is constant; find the constant arg
       and the other one.  */
      {
      tree constop = 0, varop = NULL_TREE;
      int constopnum = -1;

      if (TREE_CONSTANT (arg1))
        constopnum = 1, constop = arg1, varop = arg0;
      if (TREE_CONSTANT (arg0))
        constopnum = 0, constop = arg0, varop = arg1;

      if (constop && TREE_CODE (varop) == POSTINCREMENT_EXPR)
        {
          /* This optimization is invalid for ordered comparisons
             if CONST+INCR overflows or if foo+incr might overflow.
             This optimization is invalid for floating point due to rounding.
             For pointer types we assume overflow doesn't happen.  */
          if (POINTER_TYPE_P (TREE_TYPE (varop))
            || (! FLOAT_TYPE_P (TREE_TYPE (varop))
                && (code == EQ_EXPR || code == NE_EXPR)))
            {
            tree newconst
              = fold (build (PLUS_EXPR, TREE_TYPE (varop),
                         constop, TREE_OPERAND (varop, 1)));
            TREE_SET_CODE (varop, PREINCREMENT_EXPR);

            /* If VAROP is a reference to a bitfield, we must mask
               the constant by the width of the field.  */
            if (TREE_CODE (TREE_OPERAND (varop, 0)) == COMPONENT_REF
                && DECL_BIT_FIELD(TREE_OPERAND
                              (TREE_OPERAND (varop, 0), 1)))
              {
                int size
                  = TREE_INT_CST_LOW (DECL_SIZE
                                (TREE_OPERAND
                                 (TREE_OPERAND (varop, 0), 1)));
                tree mask, unsigned_type;
                int precision;
                tree folded_compare;

                /* First check whether the comparison would come out
                   always the same.  If we don't do that we would
                   change the meaning with the masking.  */
                if (constopnum == 0)
                  folded_compare = fold (build (code, type, constop,
                                        TREE_OPERAND (varop, 0)));
                else
                  folded_compare = fold (build (code, type,
                                        TREE_OPERAND (varop, 0),
                                        constop));
                if (integer_zerop (folded_compare)
                  || integer_onep (folded_compare))
                  return omit_one_operand (type, folded_compare, varop);

                unsigned_type = type_for_size (size, 1);
                precision = TYPE_PRECISION (unsigned_type);
                mask = build_int_2 (~0, ~0);
                TREE_TYPE (mask) = unsigned_type;
                force_fit_type (mask, 0);
                mask = const_binop (RSHIFT_EXPR, mask,
                              size_int (precision - size), 0);
                newconst = fold (build (BIT_AND_EXPR,
                                  TREE_TYPE (varop), newconst,
                                  convert (TREE_TYPE (varop),
                                         mask)));
              }
                                           

            t = build (code, type, TREE_OPERAND (t, 0),
                     TREE_OPERAND (t, 1));
            TREE_OPERAND (t, constopnum) = newconst;
            return t;
            }
        }
      else if (constop && TREE_CODE (varop) == POSTDECREMENT_EXPR)
        {
          if (POINTER_TYPE_P (TREE_TYPE (varop))
            || (! FLOAT_TYPE_P (TREE_TYPE (varop))
                && (code == EQ_EXPR || code == NE_EXPR)))
            {
            tree newconst
              = fold (build (MINUS_EXPR, TREE_TYPE (varop),
                         constop, TREE_OPERAND (varop, 1)));
            TREE_SET_CODE (varop, PREDECREMENT_EXPR);

            if (TREE_CODE (TREE_OPERAND (varop, 0)) == COMPONENT_REF
                && DECL_BIT_FIELD(TREE_OPERAND
                              (TREE_OPERAND (varop, 0), 1)))
              {
                int size
                  = TREE_INT_CST_LOW (DECL_SIZE
                                (TREE_OPERAND
                                 (TREE_OPERAND (varop, 0), 1)));
                tree mask, unsigned_type;
                int precision;
                tree folded_compare;

                if (constopnum == 0)
                  folded_compare = fold (build (code, type, constop,
                                        TREE_OPERAND (varop, 0)));
                else
                  folded_compare = fold (build (code, type,
                                        TREE_OPERAND (varop, 0),
                                        constop));
                if (integer_zerop (folded_compare)
                  || integer_onep (folded_compare))
                  return omit_one_operand (type, folded_compare, varop);

                unsigned_type = type_for_size (size, 1);
                precision = TYPE_PRECISION (unsigned_type);
                mask = build_int_2 (~0, ~0);
                TREE_TYPE (mask) = TREE_TYPE (varop);
                force_fit_type (mask, 0);
                mask = const_binop (RSHIFT_EXPR, mask,
                              size_int (precision - size), 0);
                newconst = fold (build (BIT_AND_EXPR,
                                  TREE_TYPE (varop), newconst,
                                  convert (TREE_TYPE (varop),
                                         mask)));
              }
                                           

            t = build (code, type, TREE_OPERAND (t, 0),
                     TREE_OPERAND (t, 1));
            TREE_OPERAND (t, constopnum) = newconst;
            return t;
            }
        }
      }

      /* Change X >= CST to X > (CST - 1) if CST is positive.  */
      if (TREE_CODE (arg1) == INTEGER_CST
        && TREE_CODE (arg0) != INTEGER_CST
        && tree_int_cst_sgn (arg1) > 0)
      {
        switch (TREE_CODE (t))
          {
          case GE_EXPR:
            code = GT_EXPR;
            arg1 = const_binop (MINUS_EXPR, arg1, integer_one_node, 0);
            t = build (code, type, TREE_OPERAND (t, 0), arg1);
            break;

          case LT_EXPR:
            code = LE_EXPR;
            arg1 = const_binop (MINUS_EXPR, arg1, integer_one_node, 0);
            t = build (code, type, TREE_OPERAND (t, 0), arg1);
            break;

          default:
            break;
          }
      }

      /* If this is an EQ or NE comparison with zero and ARG0 is
       (1 << foo) & bar, convert it to (bar >> foo) & 1.  Both require
       two operations, but the latter can be done in one less insn
       on machines that have only two-operand insns or on which a
       constant cannot be the first operand.  */
      if (integer_zerop (arg1) && (code == EQ_EXPR || code == NE_EXPR)
        && TREE_CODE (arg0) == BIT_AND_EXPR)
      {
        if (TREE_CODE (TREE_OPERAND (arg0, 0)) == LSHIFT_EXPR
            && integer_onep (TREE_OPERAND (TREE_OPERAND (arg0, 0), 0)))
          return
            fold (build (code, type,
                     build (BIT_AND_EXPR, TREE_TYPE (arg0),
                          build (RSHIFT_EXPR,
                               TREE_TYPE (TREE_OPERAND (arg0, 0)),
                               TREE_OPERAND (arg0, 1),
                               TREE_OPERAND (TREE_OPERAND (arg0, 0), 1)),
                          convert (TREE_TYPE (arg0),
                                 integer_one_node)),
                     arg1));
        else if (TREE_CODE (TREE_OPERAND (arg0, 1)) == LSHIFT_EXPR
               && integer_onep (TREE_OPERAND (TREE_OPERAND (arg0, 1), 0)))
          return
            fold (build (code, type,
                     build (BIT_AND_EXPR, TREE_TYPE (arg0),
                          build (RSHIFT_EXPR,
                               TREE_TYPE (TREE_OPERAND (arg0, 1)),
                               TREE_OPERAND (arg0, 0),
                               TREE_OPERAND (TREE_OPERAND (arg0, 1), 1)),
                          convert (TREE_TYPE (arg0),
                                 integer_one_node)),
                     arg1));
      }

      /* If this is an NE or EQ comparison of zero against the result of a
       signed MOD operation whose second operand is a power of 2, make
       the MOD operation unsigned since it is simpler and equivalent.  */
      if ((code == NE_EXPR || code == EQ_EXPR)
        && integer_zerop (arg1)
        && ! TREE_UNSIGNED (TREE_TYPE (arg0))
        && (TREE_CODE (arg0) == TRUNC_MOD_EXPR
            || TREE_CODE (arg0) == CEIL_MOD_EXPR
            || TREE_CODE (arg0) == FLOOR_MOD_EXPR
            || TREE_CODE (arg0) == ROUND_MOD_EXPR)
        && integer_pow2p (TREE_OPERAND (arg0, 1)))
      {
        tree newtype = unsigned_type (TREE_TYPE (arg0));
        tree newmod = build (TREE_CODE (arg0), newtype,
                         convert (newtype, TREE_OPERAND (arg0, 0)),
                         convert (newtype, TREE_OPERAND (arg0, 1)));

        return build (code, type, newmod, convert (newtype, arg1));
      }

      /* If this is an NE comparison of zero with an AND of one, remove the
       comparison since the AND will give the correct value.  */
      if (code == NE_EXPR && integer_zerop (arg1)
        && TREE_CODE (arg0) == BIT_AND_EXPR
        && integer_onep (TREE_OPERAND (arg0, 1)))
      return convert (type, arg0);

      /* If we have (A & C) == C where C is a power of 2, convert this into
       (A & C) != 0.  Similarly for NE_EXPR.  */
      if ((code == EQ_EXPR || code == NE_EXPR)
        && TREE_CODE (arg0) == BIT_AND_EXPR
        && integer_pow2p (TREE_OPERAND (arg0, 1))
        && operand_equal_p (TREE_OPERAND (arg0, 1), arg1, 0))
      return build (code == EQ_EXPR ? NE_EXPR : EQ_EXPR, type,
                  arg0, integer_zero_node);

      /* If X is unsigned, convert X < (1 << Y) into X >> Y == 0
       and similarly for >= into !=.  */
      if ((code == LT_EXPR || code == GE_EXPR)
        && TREE_UNSIGNED (TREE_TYPE (arg0))
        && TREE_CODE (arg1) == LSHIFT_EXPR
        && integer_onep (TREE_OPERAND (arg1, 0)))
      return build (code == LT_EXPR ? EQ_EXPR : NE_EXPR, type, 
                  build (RSHIFT_EXPR, TREE_TYPE (arg0), arg0,
                       TREE_OPERAND (arg1, 1)),
                  convert (TREE_TYPE (arg0), integer_zero_node));

      else if ((code == LT_EXPR || code == GE_EXPR)
             && TREE_UNSIGNED (TREE_TYPE (arg0))
             && (TREE_CODE (arg1) == NOP_EXPR
               || TREE_CODE (arg1) == CONVERT_EXPR)
             && TREE_CODE (TREE_OPERAND (arg1, 0)) == LSHIFT_EXPR
             && integer_onep (TREE_OPERAND (TREE_OPERAND (arg1, 0), 0)))
      return
        build (code == LT_EXPR ? EQ_EXPR : NE_EXPR, type,
             convert (TREE_TYPE (arg0),
                    build (RSHIFT_EXPR, TREE_TYPE (arg0), arg0,
                         TREE_OPERAND (TREE_OPERAND (arg1, 0), 1))),
             convert (TREE_TYPE (arg0), integer_zero_node));

      /* Simplify comparison of something with itself.  (For IEEE
       floating-point, we can only do some of these simplifications.)  */
      if (operand_equal_p (arg0, arg1, 0))
      {
        switch (code)
          {
          case EQ_EXPR:
          case GE_EXPR:
          case LE_EXPR:
            if (INTEGRAL_TYPE_P (TREE_TYPE (arg0)))
            return constant_boolean_node (1, type);
            code = EQ_EXPR;
            TREE_SET_CODE (t, code);
            break;

          case NE_EXPR:
            /* For NE, we can only do this simplification if integer.  */
            if (! INTEGRAL_TYPE_P (TREE_TYPE (arg0)))
            break;
            /* ... fall through ...  */
          case GT_EXPR:
          case LT_EXPR:
            return constant_boolean_node (0, type);
          default:
            abort ();
          }
      }

      /* An unsigned comparison against 0 can be simplified.  */
      if (integer_zerop (arg1)
        && (INTEGRAL_TYPE_P (TREE_TYPE (arg1))
            || POINTER_TYPE_P (TREE_TYPE (arg1)))
        && TREE_UNSIGNED (TREE_TYPE (arg1)))
      {
        switch (TREE_CODE (t))
          {
          case GT_EXPR:
            code = NE_EXPR;
            TREE_SET_CODE (t, NE_EXPR);
            break;
          case LE_EXPR:
            code = EQ_EXPR;
            TREE_SET_CODE (t, EQ_EXPR);
            break;
          case GE_EXPR:
            return omit_one_operand (type,
                               convert (type, integer_one_node),
                               arg0);
          case LT_EXPR:
            return omit_one_operand (type,
                               convert (type, integer_zero_node),
                               arg0);
          default:
            break;
          }
      }

      /* An unsigned <= 0x7fffffff can be simplified.  */
      {
      int width = TYPE_PRECISION (TREE_TYPE (arg1));
      if (TREE_CODE (arg1) == INTEGER_CST
          && ! TREE_CONSTANT_OVERFLOW (arg1)
          && width <= HOST_BITS_PER_WIDE_INT
          && TREE_INT_CST_LOW (arg1) == ((HOST_WIDE_INT) 1 << (width - 1)) - 1
          && TREE_INT_CST_HIGH (arg1) == 0
          && (INTEGRAL_TYPE_P (TREE_TYPE (arg1))
            || POINTER_TYPE_P (TREE_TYPE (arg1)))
          && TREE_UNSIGNED (TREE_TYPE (arg1)))
        {
          switch (TREE_CODE (t))
            {
            case LE_EXPR:
            return fold (build (GE_EXPR, type,
                            convert (signed_type (TREE_TYPE (arg0)),
                                   arg0),
                            convert (signed_type (TREE_TYPE (arg1)),
                                   integer_zero_node)));
            case GT_EXPR:
            return fold (build (LT_EXPR, type,
                            convert (signed_type (TREE_TYPE (arg0)),
                                   arg0),
                            convert (signed_type (TREE_TYPE (arg1)),
                                   integer_zero_node)));
            default:
            break;
            }
        }
      }

      /* If we are comparing an expression that just has comparisons
       of two integer values, arithmetic expressions of those comparisons,
       and constants, we can simplify it.  There are only three cases
       to check: the two values can either be equal, the first can be
       greater, or the second can be greater.  Fold the expression for
       those three values.  Since each value must be 0 or 1, we have
       eight possibilities, each of which corresponds to the constant 0
       or 1 or one of the six possible comparisons.

       This handles common cases like (a > b) == 0 but also handles
       expressions like  ((x > y) - (y > x)) > 0, which supposedly
       occur in macroized code.  */

      if (TREE_CODE (arg1) == INTEGER_CST && TREE_CODE (arg0) != INTEGER_CST)
      {
        tree cval1 = 0, cval2 = 0;
        int save_p = 0;

        if (twoval_comparison_p (arg0, &cval1, &cval2, &save_p)
            /* Don't handle degenerate cases here; they should already
             have been handled anyway.  */
            && cval1 != 0 && cval2 != 0
            && ! (TREE_CONSTANT (cval1) && TREE_CONSTANT (cval2))
            && TREE_TYPE (cval1) == TREE_TYPE (cval2)
            && INTEGRAL_TYPE_P (TREE_TYPE (cval1))
            && TYPE_MAX_VALUE (TREE_TYPE (cval1))
            && TYPE_MAX_VALUE (TREE_TYPE (cval2))
            && ! operand_equal_p (TYPE_MIN_VALUE (TREE_TYPE (cval1)),
                            TYPE_MAX_VALUE (TREE_TYPE (cval2)), 0))
          {
            tree maxval = TYPE_MAX_VALUE (TREE_TYPE (cval1));
            tree minval = TYPE_MIN_VALUE (TREE_TYPE (cval1));

            /* We can't just pass T to eval_subst in case cval1 or cval2
             was the same as ARG1.  */

            tree high_result
            = fold (build (code, type,
                         eval_subst (arg0, cval1, maxval, cval2, minval),
                         arg1));
            tree equal_result
            = fold (build (code, type,
                         eval_subst (arg0, cval1, maxval, cval2, maxval),
                         arg1));
            tree low_result
            = fold (build (code, type,
                         eval_subst (arg0, cval1, minval, cval2, maxval),
                         arg1));

            /* All three of these results should be 0 or 1.  Confirm they
             are.  Then use those values to select the proper code
             to use.  */

            if ((integer_zerop (high_result)
               || integer_onep (high_result))
              && (integer_zerop (equal_result)
                  || integer_onep (equal_result))
              && (integer_zerop (low_result)
                  || integer_onep (low_result)))
            {
              /* Make a 3-bit mask with the high-order bit being the
                 value for `>', the next for '=', and the low for '<'.  */
              switch ((integer_onep (high_result) * 4)
                    + (integer_onep (equal_result) * 2)
                    + integer_onep (low_result))
                {
                case 0:
                  /* Always false.  */
                  return omit_one_operand (type, integer_zero_node, arg0);
                case 1:
                  code = LT_EXPR;
                  break;
                case 2:
                  code = EQ_EXPR;
                  break;
                case 3:
                  code = LE_EXPR;
                  break;
                case 4:
                  code = GT_EXPR;
                  break;
                case 5:
                  code = NE_EXPR;
                  break;
                case 6:
                  code = GE_EXPR;
                  break;
                case 7:
                  /* Always true.  */
                  return omit_one_operand (type, integer_one_node, arg0);
                }

              t = build (code, type, cval1, cval2);
              if (save_p)
                return save_expr (t);
              else
                return fold (t);
            }
          }
      }

      /* If this is a comparison of a field, we may be able to simplify it.  */
      if ((TREE_CODE (arg0) == COMPONENT_REF
         || TREE_CODE (arg0) == BIT_FIELD_REF)
        && (code == EQ_EXPR || code == NE_EXPR)
        /* Handle the constant case even without -O
           to make sure the warnings are given.  */
        && (optimize || TREE_CODE (arg1) == INTEGER_CST))
      {
        t1 = optimize_bit_field_compare (code, type, arg0, arg1);
        return t1 ? t1 : t;
      }

      /* If this is a comparison of complex values and either or both sides
       are a COMPLEX_EXPR or COMPLEX_CST, it is best to split up the
       comparisons and join them with a TRUTH_ANDIF_EXPR or TRUTH_ORIF_EXPR.
       This may prevent needless evaluations.  */
      if ((code == EQ_EXPR || code == NE_EXPR)
        && TREE_CODE (TREE_TYPE (arg0)) == COMPLEX_TYPE
        && (TREE_CODE (arg0) == COMPLEX_EXPR
            || TREE_CODE (arg1) == COMPLEX_EXPR
            || TREE_CODE (arg0) == COMPLEX_CST
            || TREE_CODE (arg1) == COMPLEX_CST))
      {
        tree subtype = TREE_TYPE (TREE_TYPE (arg0));
        tree real0, imag0, real1, imag1;

        arg0 = save_expr (arg0);
        arg1 = save_expr (arg1);
        real0 = fold (build1 (REALPART_EXPR, subtype, arg0));
        imag0 = fold (build1 (IMAGPART_EXPR, subtype, arg0));
        real1 = fold (build1 (REALPART_EXPR, subtype, arg1));
        imag1 = fold (build1 (IMAGPART_EXPR, subtype, arg1));

        return fold (build ((code == EQ_EXPR ? TRUTH_ANDIF_EXPR
                         : TRUTH_ORIF_EXPR),
                        type,
                        fold (build (code, type, real0, real1)),
                        fold (build (code, type, imag0, imag1))));
      }

      /* From here on, the only cases we handle are when the result is
       known to be a constant.

       To compute GT, swap the arguments and do LT.
       To compute GE, do LT and invert the result.
       To compute LE, swap the arguments, do LT and invert the result.
       To compute NE, do EQ and invert the result.

       Therefore, the code below must handle only EQ and LT.  */

      if (code == LE_EXPR || code == GT_EXPR)
      {
        tem = arg0, arg0 = arg1, arg1 = tem;
        code = swap_tree_comparison (code);
      }

      /* Note that it is safe to invert for real values here because we
       will check below in the one case that it matters.  */

      invert = 0;
      if (code == NE_EXPR || code == GE_EXPR)
      {
        invert = 1;
        code = invert_tree_comparison (code);
      }

      /* Compute a result for LT or EQ if args permit;
       otherwise return T.  */
      if (TREE_CODE (arg0) == INTEGER_CST && TREE_CODE (arg1) == INTEGER_CST)
      {
        if (code == EQ_EXPR)
          t1 = build_int_2 ((TREE_INT_CST_LOW (arg0)
                         == TREE_INT_CST_LOW (arg1))
                        && (TREE_INT_CST_HIGH (arg0)
                          == TREE_INT_CST_HIGH (arg1)),
                        0);
        else
          t1 = build_int_2 ((TREE_UNSIGNED (TREE_TYPE (arg0))
                         ? INT_CST_LT_UNSIGNED (arg0, arg1)
                         : INT_CST_LT (arg0, arg1)),
                        0);
      }

#if 0 /* This is no longer useful, but breaks some real code.  */
      /* Assume a nonexplicit constant cannot equal an explicit one,
       since such code would be undefined anyway.
       Exception: on sysvr4, using #pragma weak,
       a label can come out as 0.  */
      else if (TREE_CODE (arg1) == INTEGER_CST
             && !integer_zerop (arg1)
             && TREE_CONSTANT (arg0)
             && TREE_CODE (arg0) == ADDR_EXPR
             && code == EQ_EXPR)
      t1 = build_int_2 (0, 0);
#endif
      /* Two real constants can be compared explicitly.  */
      else if (TREE_CODE (arg0) == REAL_CST && TREE_CODE (arg1) == REAL_CST)
      {
        /* If either operand is a NaN, the result is false with two
           exceptions: First, an NE_EXPR is true on NaNs, but that case
           is already handled correctly since we will be inverting the
           result for NE_EXPR.  Second, if we had inverted a LE_EXPR
           or a GE_EXPR into a LT_EXPR, we must return true so that it
           will be inverted into false.  */

        if (REAL_VALUE_ISNAN (TREE_REAL_CST (arg0))
            || REAL_VALUE_ISNAN (TREE_REAL_CST (arg1)))
          t1 = build_int_2 (invert && code == LT_EXPR, 0);

        else if (code == EQ_EXPR)
          t1 = build_int_2 (REAL_VALUES_EQUAL (TREE_REAL_CST (arg0),
                                     TREE_REAL_CST (arg1)),
                        0);
        else
          t1 = build_int_2 (REAL_VALUES_LESS (TREE_REAL_CST (arg0),
                                    TREE_REAL_CST (arg1)),
                        0);
      }

      if (t1 == NULL_TREE)
      return t;

      if (invert)
      TREE_INT_CST_LOW (t1) ^= 1;

      TREE_TYPE (t1) = type;
      if (TREE_CODE (type) == BOOLEAN_TYPE)
      return truthvalue_conversion (t1);
      return t1;

    case COND_EXPR:
      /* Pedantic ANSI C says that a conditional expression is never an lvalue,
       so all simple results must be passed through pedantic_non_lvalue.  */
      if (TREE_CODE (arg0) == INTEGER_CST)
      return pedantic_non_lvalue
        (TREE_OPERAND (t, (integer_zerop (arg0) ? 2 : 1)));
      else if (operand_equal_p (arg1, TREE_OPERAND (expr, 2), 0))
      return pedantic_omit_one_operand (type, arg1, arg0);

      /* If the second operand is zero, invert the comparison and swap
       the second and third operands.  Likewise if the second operand
       is constant and the third is not or if the third operand is
       equivalent to the first operand of the comparison.  */

      if (integer_zerop (arg1)
        || (TREE_CONSTANT (arg1) && ! TREE_CONSTANT (TREE_OPERAND (t, 2)))
        || (TREE_CODE_CLASS (TREE_CODE (arg0)) == '<'
            && operand_equal_for_comparison_p (TREE_OPERAND (arg0, 0),
                                     TREE_OPERAND (t, 2),
                                     TREE_OPERAND (arg0, 1))))
      {
        /* See if this can be inverted.  If it can't, possibly because
           it was a floating-point inequality comparison, don't do
           anything.  */
        tem = invert_truthvalue (arg0);

        if (TREE_CODE (tem) != TRUTH_NOT_EXPR)
          {
            t = build (code, type, tem,
                   TREE_OPERAND (t, 2), TREE_OPERAND (t, 1));
            arg0 = tem;
            arg1 = TREE_OPERAND (t, 2);
            STRIP_NOPS (arg1);
          }
      }

      /* If we have A op B ? A : C, we may be able to convert this to a
       simpler expression, depending on the operation and the values
       of B and C.  IEEE floating point prevents this though,
       because A or B might be -0.0 or a NaN.  */

      if (TREE_CODE_CLASS (TREE_CODE (arg0)) == '<'
        && (TARGET_FLOAT_FORMAT != IEEE_FLOAT_FORMAT
            || ! FLOAT_TYPE_P (TREE_TYPE (TREE_OPERAND (arg0, 0)))
            || flag_fast_math)
        && operand_equal_for_comparison_p (TREE_OPERAND (arg0, 0),
                                   arg1, TREE_OPERAND (arg0, 1)))
      {
        tree arg2 = TREE_OPERAND (t, 2);
        enum tree_code comp_code = TREE_CODE (arg0);

        STRIP_NOPS (arg2);

        /* If we have A op 0 ? A : -A, this is A, -A, abs (A), or abs (-A),
           depending on the comparison operation.  */
        if ((FLOAT_TYPE_P (TREE_TYPE (TREE_OPERAND (arg0, 1)))
             ? real_zerop (TREE_OPERAND (arg0, 1))
             : integer_zerop (TREE_OPERAND (arg0, 1)))
            && TREE_CODE (arg2) == NEGATE_EXPR
            && operand_equal_p (TREE_OPERAND (arg2, 0), arg1, 0))
          switch (comp_code)
            {
            case EQ_EXPR:
            return pedantic_non_lvalue
              (fold (build1 (NEGATE_EXPR, type, arg1)));
            case NE_EXPR:
            return pedantic_non_lvalue (convert (type, arg1));
            case GE_EXPR:
            case GT_EXPR:
            return pedantic_non_lvalue
              (convert (type, fold (build1 (ABS_EXPR,
                                    TREE_TYPE (arg1), arg1))));
            case LE_EXPR:
            case LT_EXPR:
            return pedantic_non_lvalue
              (fold (build1 (NEGATE_EXPR, type,
                         convert (type,
                                fold (build1 (ABS_EXPR,
                                          TREE_TYPE (arg1),
                                          arg1))))));
            default:
            abort ();
            }

        /* If this is A != 0 ? A : 0, this is simply A.  For ==, it is
           always zero.  */

        if (integer_zerop (TREE_OPERAND (arg0, 1)) && integer_zerop (arg2))
          {
            if (comp_code == NE_EXPR)
            return pedantic_non_lvalue (convert (type, arg1));
            else if (comp_code == EQ_EXPR)
            return pedantic_non_lvalue (convert (type, integer_zero_node));
          }

        /* If this is A op B ? A : B, this is either A, B, min (A, B),
           or max (A, B), depending on the operation.  */

        if (operand_equal_for_comparison_p (TREE_OPERAND (arg0, 1),
                                    arg2, TREE_OPERAND (arg0, 0)))
          {
            tree comp_op0 = TREE_OPERAND (arg0, 0);
            tree comp_op1 = TREE_OPERAND (arg0, 1);
            tree comp_type = TREE_TYPE (comp_op0);

            switch (comp_code)
            {
            case EQ_EXPR:
              return pedantic_non_lvalue (convert (type, arg2));
            case NE_EXPR:
              return pedantic_non_lvalue (convert (type, arg1));
            case LE_EXPR:
            case LT_EXPR:
              /* In C++ a ?: expression can be an lvalue, so put the
                 operand which will be used if they are equal first
                 so that we can convert this back to the 
                 corresponding COND_EXPR.  */
              return pedantic_non_lvalue
                (convert (type, (fold (build (MIN_EXPR, comp_type,
                                      (comp_code == LE_EXPR
                                       ? comp_op0 : comp_op1),
                                      (comp_code == LE_EXPR
                                       ? comp_op1 : comp_op0))))));
              break;
            case GE_EXPR:
            case GT_EXPR:
              return pedantic_non_lvalue
                (convert (type, fold (build (MAX_EXPR, comp_type,
                                     (comp_code == GE_EXPR
                                      ? comp_op0 : comp_op1),
                                     (comp_code == GE_EXPR
                                      ? comp_op1 : comp_op0)))));
              break;
            default:
              abort ();
            }
          }

        /* If this is A op C1 ? A : C2 with C1 and C2 constant integers,
           we might still be able to simplify this.  For example,
           if C1 is one less or one more than C2, this might have started
           out as a MIN or MAX and been transformed by this function.
           Only good for INTEGER_TYPEs, because we need TYPE_MAX_VALUE.  */

        if (INTEGRAL_TYPE_P (type)
            && TREE_CODE (TREE_OPERAND (arg0, 1)) == INTEGER_CST
            && TREE_CODE (arg2) == INTEGER_CST)
          switch (comp_code)
            {
            case EQ_EXPR:
            /* We can replace A with C1 in this case.  */
            arg1 = convert (type, TREE_OPERAND (arg0, 1));
            t = build (code, type, TREE_OPERAND (t, 0), arg1,
                     TREE_OPERAND (t, 2));
            break;

            case LT_EXPR:
            /* If C1 is C2 + 1, this is min(A, C2).  */
            if (! operand_equal_p (arg2, TYPE_MAX_VALUE (type), 1)
                && operand_equal_p (TREE_OPERAND (arg0, 1),
                              const_binop (PLUS_EXPR, arg2,
                                         integer_one_node, 0), 1))
              return pedantic_non_lvalue
                (fold (build (MIN_EXPR, type, arg1, arg2)));
            break;

            case LE_EXPR:
            /* If C1 is C2 - 1, this is min(A, C2).  */
            if (! operand_equal_p (arg2, TYPE_MIN_VALUE (type), 1)
                && operand_equal_p (TREE_OPERAND (arg0, 1),
                              const_binop (MINUS_EXPR, arg2,
                                         integer_one_node, 0), 1))
              return pedantic_non_lvalue
                (fold (build (MIN_EXPR, type, arg1, arg2)));
            break;

            case GT_EXPR:
            /* If C1 is C2 - 1, this is max(A, C2).  */
            if (! operand_equal_p (arg2, TYPE_MIN_VALUE (type), 1)
                && operand_equal_p (TREE_OPERAND (arg0, 1),
                              const_binop (MINUS_EXPR, arg2,
                                         integer_one_node, 0), 1))
              return pedantic_non_lvalue
                (fold (build (MAX_EXPR, type, arg1, arg2)));
            break;

            case GE_EXPR:
            /* If C1 is C2 + 1, this is max(A, C2).  */
            if (! operand_equal_p (arg2, TYPE_MAX_VALUE (type), 1)
                && operand_equal_p (TREE_OPERAND (arg0, 1),
                              const_binop (PLUS_EXPR, arg2,
                                         integer_one_node, 0), 1))
              return pedantic_non_lvalue
                (fold (build (MAX_EXPR, type, arg1, arg2)));
            break;
            case NE_EXPR:
            break;
            default:
            abort ();
            }
      }

      /* If the second operand is simpler than the third, swap them
       since that produces better jump optimization results.  */
      if ((TREE_CONSTANT (arg1) || TREE_CODE_CLASS (TREE_CODE (arg1)) == 'd'
         || TREE_CODE (arg1) == SAVE_EXPR)
        && ! (TREE_CONSTANT (TREE_OPERAND (t, 2))
            || TREE_CODE_CLASS (TREE_CODE (TREE_OPERAND (t, 2))) == 'd'
            || TREE_CODE (TREE_OPERAND (t, 2)) == SAVE_EXPR))
      {
        /* See if this can be inverted.  If it can't, possibly because
           it was a floating-point inequality comparison, don't do
           anything.  */
        tem = invert_truthvalue (arg0);

        if (TREE_CODE (tem) != TRUTH_NOT_EXPR)
          {
            t = build (code, type, tem,
                   TREE_OPERAND (t, 2), TREE_OPERAND (t, 1));
            arg0 = tem;
            arg1 = TREE_OPERAND (t, 2);
            STRIP_NOPS (arg1);
          }
      }

      /* Convert A ? 1 : 0 to simply A.  */
      if (integer_onep (TREE_OPERAND (t, 1))
        && integer_zerop (TREE_OPERAND (t, 2))
        /* If we try to convert TREE_OPERAND (t, 0) to our type, the
           call to fold will try to move the conversion inside 
           a COND, which will recurse.  In that case, the COND_EXPR
           is probably the best choice, so leave it alone.  */
        && type == TREE_TYPE (arg0))
      return pedantic_non_lvalue (arg0);

      /* Look for expressions of the form A & 2 ? 2 : 0.  The result of this
       operation is simply A & 2.  */

      if (integer_zerop (TREE_OPERAND (t, 2))
        && TREE_CODE (arg0) == NE_EXPR
        && integer_zerop (TREE_OPERAND (arg0, 1))
        && integer_pow2p (arg1)
        && TREE_CODE (TREE_OPERAND (arg0, 0)) == BIT_AND_EXPR
        && operand_equal_p (TREE_OPERAND (TREE_OPERAND (arg0, 0), 1),
                        arg1, 1))
      return pedantic_non_lvalue (convert (type, TREE_OPERAND (arg0, 0)));

      return t;

    case COMPOUND_EXPR:
      /* When pedantic, a compound expression can be neither an lvalue
       nor an integer constant expression.  */
      if (TREE_SIDE_EFFECTS (arg0) || pedantic)
      return t;
      /* Don't let (0, 0) be null pointer constant.  */
      if (integer_zerop (arg1))
      return non_lvalue (arg1);
      return arg1;

    case COMPLEX_EXPR:
      if (wins)
      return build_complex (type, arg0, arg1);
      return t;

    case REALPART_EXPR:
      if (TREE_CODE (TREE_TYPE (arg0)) != COMPLEX_TYPE)
      return t;
      else if (TREE_CODE (arg0) == COMPLEX_EXPR)
      return omit_one_operand (type, TREE_OPERAND (arg0, 0),
                         TREE_OPERAND (arg0, 1));
      else if (TREE_CODE (arg0) == COMPLEX_CST)
      return TREE_REALPART (arg0);
      else if (TREE_CODE (arg0) == PLUS_EXPR || TREE_CODE (arg0) == MINUS_EXPR)
      return fold (build (TREE_CODE (arg0), type,
                      fold (build1 (REALPART_EXPR, type,
                                TREE_OPERAND (arg0, 0))),
                      fold (build1 (REALPART_EXPR,
                                type, TREE_OPERAND (arg0, 1)))));
      return t;

    case IMAGPART_EXPR:
      if (TREE_CODE (TREE_TYPE (arg0)) != COMPLEX_TYPE)
      return convert (type, integer_zero_node);
      else if (TREE_CODE (arg0) == COMPLEX_EXPR)
      return omit_one_operand (type, TREE_OPERAND (arg0, 1),
                         TREE_OPERAND (arg0, 0));
      else if (TREE_CODE (arg0) == COMPLEX_CST)
      return TREE_IMAGPART (arg0);
      else if (TREE_CODE (arg0) == PLUS_EXPR || TREE_CODE (arg0) == MINUS_EXPR)
      return fold (build (TREE_CODE (arg0), type,
                      fold (build1 (IMAGPART_EXPR, type,
                                TREE_OPERAND (arg0, 0))),
                      fold (build1 (IMAGPART_EXPR, type,
                                TREE_OPERAND (arg0, 1)))));
      return t;

      /* Pull arithmetic ops out of the CLEANUP_POINT_EXPR where
         appropriate.  */
    case CLEANUP_POINT_EXPR:
      if (! has_cleanups (arg0))
      return TREE_OPERAND (t, 0);

      {
      enum tree_code code0 = TREE_CODE (arg0);
      int kind0 = TREE_CODE_CLASS (code0);
      tree arg00 = TREE_OPERAND (arg0, 0);
      tree arg01;

      if (kind0 == '1' || code0 == TRUTH_NOT_EXPR)
        return fold (build1 (code0, type, 
                         fold (build1 (CLEANUP_POINT_EXPR,
                                   TREE_TYPE (arg00), arg00))));

      if (kind0 == '<' || kind0 == '2'
          || code0 == TRUTH_ANDIF_EXPR || code0 == TRUTH_ORIF_EXPR
          || code0 == TRUTH_AND_EXPR   || code0 == TRUTH_OR_EXPR
          || code0 == TRUTH_XOR_EXPR)
        {
          arg01 = TREE_OPERAND (arg0, 1);

          if (TREE_CONSTANT (arg00)
            || ((code0 == TRUTH_ANDIF_EXPR || code0 == TRUTH_ORIF_EXPR)
                && ! has_cleanups (arg00)))
            return fold (build (code0, type, arg00,
                          fold (build1 (CLEANUP_POINT_EXPR,
                                    TREE_TYPE (arg01), arg01))));

          if (TREE_CONSTANT (arg01))
            return fold (build (code0, type,
                          fold (build1 (CLEANUP_POINT_EXPR,
                                    TREE_TYPE (arg00), arg00)),
                          arg01));
        }

      return t;
      }

    default:
      return t;
    } /* switch (code) */
}

/* Determine if first argument is a multiple of second argument.
   Return 0 if it is not, or is not easily determined to so be.

   An example of the sort of thing we care about (at this point --
   this routine could surely be made more general, and expanded
   to do what the *_DIV_EXPR's fold() cases do now) is discovering
   that

     SAVE_EXPR (I) * SAVE_EXPR (J * 8)

   is a multiple of

     SAVE_EXPR (J * 8)

   when we know that the two `SAVE_EXPR (J * 8)' nodes are the
   same node (which means they will have the same value at run
   time, even though we don't know when they'll be assigned).

   This code also handles discovering that

     SAVE_EXPR (I) * SAVE_EXPR (J * 8)

   is a multiple of

     8

   (of course) so we don't have to worry about dealing with a
   possible remainder.

   Note that we _look_ inside a SAVE_EXPR only to determine
   how it was calculated; it is not safe for fold() to do much
   of anything else with the internals of a SAVE_EXPR, since
   fold() cannot know when it will be evaluated at run time.
   For example, the latter example above _cannot_ be implemented
   as

     SAVE_EXPR (I) * J

   or any variant thereof, since the value of J at evaluation time
   of the original SAVE_EXPR is not necessarily the same at the time
   the new expression is evaluated.  The only optimization of this
   sort that would be valid is changing

     SAVE_EXPR (I) * SAVE_EXPR (SAVE_EXPR (J) * 8)
   divided by
     8

   to

     SAVE_EXPR (I) * SAVE_EXPR (J)

   (where the same SAVE_EXPR (J) is used in the original and the
   transformed version).  */

static int
multiple_of_p (type, top, bottom)
     tree type;
     tree top;
     tree bottom;
{
  if (operand_equal_p (top, bottom, 0))
    return 1;

  if (TREE_CODE (type) != INTEGER_TYPE)
    return 0;

  switch (TREE_CODE (top))
    {
    case MULT_EXPR:
      return (multiple_of_p (type, TREE_OPERAND (top, 0), bottom)
            || multiple_of_p (type, TREE_OPERAND (top, 1), bottom));

    case PLUS_EXPR:
    case MINUS_EXPR:
      return (multiple_of_p (type, TREE_OPERAND (top, 0), bottom)
            && multiple_of_p (type, TREE_OPERAND (top, 1), bottom));

    case NOP_EXPR:
      /* Punt if conversion from non-integral or wider integral type.  */
      if ((TREE_CODE (TREE_TYPE (TREE_OPERAND (top, 0))) != INTEGER_TYPE)
        || (TYPE_PRECISION (type)
            < TYPE_PRECISION (TREE_TYPE (TREE_OPERAND (top, 0)))))
      return 0;
      /* Fall through. */
    case SAVE_EXPR:
      return multiple_of_p (type, TREE_OPERAND (top, 0), bottom);

    case INTEGER_CST:
      if ((TREE_CODE (bottom) != INTEGER_CST)
        || (tree_int_cst_sgn (top) < 0)
        || (tree_int_cst_sgn (bottom) < 0))
      return 0;
      return integer_zerop (const_binop (TRUNC_MOD_EXPR,
                               top, bottom, 0));

    default:
      return 0;
    }
}


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