[gcc/gcc.git] / gcc / fold-const.c

/* Fold a constant sub-tree into a single node for C-compiler
   Copyright (C) 1987, 1988, 1992, 1993, 1994, 1995, 1996, 1997, 1998, 1999,
   2000, 2001, 2002, 2003, 2004 Free Software Foundation, Inc.

This file is part of GCC.

GCC 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.

GCC 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 GCC; 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 "coretypes.h"
#include "tm.h"
#include "flags.h"
#include "tree.h"
#include "real.h"
#include "rtl.h"
#include "expr.h"
#include "tm_p.h"
#include "toplev.h"
#include "ggc.h"
#include "hashtab.h"
#include "langhooks.h"
#include "md5.h"

static void encode (HOST_WIDE_INT *, unsigned HOST_WIDE_INT, HOST_WIDE_INT);
static void decode (HOST_WIDE_INT *, unsigned HOST_WIDE_INT *, HOST_WIDE_INT *);
static bool negate_mathfn_p (enum built_in_function);
static bool negate_expr_p (tree);
static tree negate_expr (tree);
static tree split_tree (tree, enum tree_code, tree *, tree *, tree *, int);
static tree associate_trees (tree, tree, enum tree_code, tree);
static tree int_const_binop (enum tree_code, tree, tree, int);
static tree const_binop (enum tree_code, tree, tree, int);
static hashval_t size_htab_hash (const void *);
static int size_htab_eq (const void *, const void *);
static tree fold_convert_const (enum tree_code, tree, tree);
static tree fold_convert (tree, tree);
static enum tree_code invert_tree_comparison (enum tree_code);
static enum tree_code swap_tree_comparison (enum tree_code);
static int comparison_to_compcode (enum tree_code);
static enum tree_code compcode_to_comparison (int);
static int truth_value_p (enum tree_code);
static int operand_equal_for_comparison_p (tree, tree, tree);
static int twoval_comparison_p (tree, tree *, tree *, int *);
static tree eval_subst (tree, tree, tree, tree, tree);
static tree pedantic_omit_one_operand (tree, tree, tree);
static tree distribute_bit_expr (enum tree_code, tree, tree, tree);
static tree make_bit_field_ref (tree, tree, int, int, int);
static tree optimize_bit_field_compare (enum tree_code, tree, tree, tree);
static tree decode_field_reference (tree, HOST_WIDE_INT *, HOST_WIDE_INT *,
                                    enum machine_mode *, int *, int *,
                                    tree *, tree *);
static int all_ones_mask_p (tree, int);
static tree sign_bit_p (tree, tree);
static int simple_operand_p (tree);
static tree range_binop (enum tree_code, tree, tree, int, tree, int);
static tree make_range (tree, int *, tree *, tree *);
static tree build_range_check (tree, tree, int, tree, tree);
static int merge_ranges (int *, tree *, tree *, int, tree, tree, int, tree,
                         tree);
static tree fold_range_test (tree);
static tree unextend (tree, int, int, tree);
static tree fold_truthop (enum tree_code, tree, tree, tree);
static tree optimize_minmax_comparison (tree);
static tree extract_muldiv (tree, tree, enum tree_code, tree);
static tree extract_muldiv_1 (tree, tree, enum tree_code, tree);
static tree strip_compound_expr (tree, tree);
static int multiple_of_p (tree, tree, tree);
static tree constant_boolean_node (int, tree);
static int count_cond (tree, int);
static tree fold_binary_op_with_conditional_arg (enum tree_code, tree, tree,
                                                 tree, int);
static bool fold_real_zero_addition_p (tree, tree, int);
static tree fold_mathfn_compare (enum built_in_function, enum tree_code,
                                 tree, tree, tree);
static tree fold_inf_compare (enum tree_code, tree, tree, tree);
static bool reorder_operands_p (tree, tree);
static bool tree_swap_operands_p (tree, tree, bool);

static tree fold_negate_const (tree, tree);
static tree fold_abs_const (tree, tree);
static tree fold_relational_const (enum tree_code, tree, tree, tree);

/* The following constants represent a bit based encoding of GCC's
   comparison operators.  This encoding simplifies transformations
   on relational comparison operators, such as AND and OR.  */
#define COMPCODE_FALSE   0
#define COMPCODE_LT      1
#define COMPCODE_EQ      2
#define COMPCODE_LE      3
#define COMPCODE_GT      4
#define COMPCODE_NE      5
#define COMPCODE_GE      6
#define COMPCODE_TRUE    7

/* We know that A1 + B1 = SUM1, using 2's complement arithmetic and 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)
\f
/* 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.  The value of the word is LOWPART + HIGHPART * BASE.  */

#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 (HOST_WIDE_INT *words, unsigned HOST_WIDE_INT low, HOST_WIDE_INT 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 (HOST_WIDE_INT *words, unsigned HOST_WIDE_INT *low,
        HOST_WIDE_INT *hi)
{
  *low = words[0] + words[1] * BASE;
  *hi = words[2] + words[3] * BASE;
}
\f
/* 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.

   Return 1 if a signed overflow occurs, 0 otherwise.  If OVERFLOW is
   nonzero, a signed overflow has already occurred in calculating T, so
   propagate it.  */

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

  if (TREE_CODE (t) == REAL_CST)
    {
      /* ??? Used to check for overflow here via CHECK_FLOAT_TYPE.
         Consider doing it via real_convert now.  */
      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))
      || TREE_CODE (TREE_TYPE (t)) == OFFSET_TYPE)
    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) &= ~((unsigned HOST_WIDE_INT) (-1) << prec);
    }

  /* Unsigned types do not suffer sign extension or overflow unless they
     are a sizetype.  */
  if (TYPE_UNSIGNED (TREE_TYPE (t))
      && ! (TREE_CODE (TREE_TYPE (t)) == INTEGER_TYPE
            && TYPE_IS_SIZETYPE (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
          ? 0 != (TREE_INT_CST_HIGH (t)
                  & ((HOST_WIDE_INT) 1
                     << (prec - HOST_BITS_PER_WIDE_INT - 1)))
          : 0 != (TREE_INT_CST_LOW (t)
                  & ((unsigned 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) |= ((unsigned HOST_WIDE_INT) (-1) << prec);
        }
    }

  /* Return nonzero if signed overflow occurred.  */
  return
    ((overflow | (low ^ TREE_INT_CST_LOW (t)) | (high ^ TREE_INT_CST_HIGH (t)))
     != 0);
}
\f
/* 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 (unsigned HOST_WIDE_INT l1, HOST_WIDE_INT h1,
            unsigned HOST_WIDE_INT l2, HOST_WIDE_INT h2,
            unsigned HOST_WIDE_INT *lv, HOST_WIDE_INT *hv)
{
  unsigned HOST_WIDE_INT l;
  HOST_WIDE_INT h;

  l = l1 + l2;
  h = h1 + h2 + (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 (unsigned HOST_WIDE_INT l1, HOST_WIDE_INT h1,
            unsigned HOST_WIDE_INT *lv, HOST_WIDE_INT *hv)
{
  if (l1 == 0)
    {
      *lv = 0;
      *hv = - h1;
      return (*hv & h1) < 0;
    }
  else
    {
      *lv = -l1;
      *hv = ~h1;
      return 0;
    }
}
\f
/* 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 (unsigned HOST_WIDE_INT l1, HOST_WIDE_INT h1,
            unsigned HOST_WIDE_INT l2, HOST_WIDE_INT h2,
            unsigned HOST_WIDE_INT *lv, HOST_WIDE_INT *hv)
{
  HOST_WIDE_INT arg1[4];
  HOST_WIDE_INT arg2[4];
  HOST_WIDE_INT prod[4 * 2];
  unsigned HOST_WIDE_INT carry;
  int i, j, k;
  unsigned HOST_WIDE_INT toplow, neglow;
  HOST_WIDE_INT tophigh, neghigh;

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

  memset (prod, 0, 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;
}
\f
/* 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 (unsigned HOST_WIDE_INT l1, HOST_WIDE_INT h1,
               HOST_WIDE_INT count, unsigned int prec,
               unsigned HOST_WIDE_INT *lv, HOST_WIDE_INT *hv, int arith)
{
  unsigned HOST_WIDE_INT signmask;

  if (count < 0)
    {
      rshift_double (l1, h1, -count, prec, lv, hv, arith);
      return;
    }

  if (SHIFT_COUNT_TRUNCATED)
    count %= prec;

  if (count >= 2 * HOST_BITS_PER_WIDE_INT)
    {
      /* Shifting by the host word size is undefined according to the
         ANSI standard, so we must handle this as a special case.  */
      *hv = 0;
      *lv = 0;
    }
  else if (count >= HOST_BITS_PER_WIDE_INT)
    {
      *hv = l1 << (count - HOST_BITS_PER_WIDE_INT);
      *lv = 0;
    }
  else
    {
      *hv = (((unsigned HOST_WIDE_INT) h1 << count)
             | (l1 >> (HOST_BITS_PER_WIDE_INT - count - 1) >> 1));
      *lv = l1 << count;
    }

  /* Sign extend all bits that are beyond the precision.  */

  signmask = -((prec > HOST_BITS_PER_WIDE_INT
                ? ((unsigned HOST_WIDE_INT) *hv
                   >> (prec - HOST_BITS_PER_WIDE_INT - 1))
                : (*lv >> (prec - 1))) & 1);

  if (prec >= 2 * HOST_BITS_PER_WIDE_INT)
    ;
  else if (prec >= HOST_BITS_PER_WIDE_INT)
    {
      *hv &= ~((HOST_WIDE_INT) (-1) << (prec - HOST_BITS_PER_WIDE_INT));
      *hv |= signmask << (prec - HOST_BITS_PER_WIDE_INT);
    }
  else
    {
      *hv = signmask;
      *lv &= ~((unsigned HOST_WIDE_INT) (-1) << prec);
      *lv |= signmask << prec;
    }
}

/* 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 (unsigned HOST_WIDE_INT l1, HOST_WIDE_INT h1,
               HOST_WIDE_INT count, unsigned int prec,
               unsigned HOST_WIDE_INT *lv, HOST_WIDE_INT *hv,
               int arith)
{
  unsigned HOST_WIDE_INT signmask;

  signmask = (arith
              ? -((unsigned HOST_WIDE_INT) h1 >> (HOST_BITS_PER_WIDE_INT - 1))
              : 0);

  if (SHIFT_COUNT_TRUNCATED)
    count %= prec;

  if (count >= 2 * HOST_BITS_PER_WIDE_INT)
    {
      /* Shifting by the host word size is undefined according to the
         ANSI standard, so we must handle this as a special case.  */
      *hv = 0;
      *lv = 0;
    }
  else if (count >= HOST_BITS_PER_WIDE_INT)
    {
      *hv = 0;
      *lv = (unsigned HOST_WIDE_INT) h1 >> (count - HOST_BITS_PER_WIDE_INT);
    }
  else
    {
      *hv = (unsigned HOST_WIDE_INT) h1 >> count;
      *lv = ((l1 >> count)
             | ((unsigned HOST_WIDE_INT) h1 << (HOST_BITS_PER_WIDE_INT - count - 1) << 1));
    }

  /* Zero / sign extend all bits that are beyond the precision.  */

  if (count >= (HOST_WIDE_INT)prec)
    {
      *hv = signmask;
      *lv = signmask;
    }
  else if ((prec - count) >= 2 * HOST_BITS_PER_WIDE_INT)
    ;
  else if ((prec - count) >= HOST_BITS_PER_WIDE_INT)
    {
      *hv &= ~((HOST_WIDE_INT) (-1) << (prec - count - HOST_BITS_PER_WIDE_INT));
      *hv |= signmask << (prec - count - HOST_BITS_PER_WIDE_INT);
    }
  else
    {
      *hv = signmask;
      *lv &= ~((unsigned HOST_WIDE_INT) (-1) << (prec - count));
      *lv |= signmask << (prec - count);
    }
}
\f
/* 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 (unsigned HOST_WIDE_INT l1, HOST_WIDE_INT h1,
                HOST_WIDE_INT count, unsigned int prec,
                unsigned HOST_WIDE_INT *lv, HOST_WIDE_INT *hv)
{
  unsigned HOST_WIDE_INT s1l, s2l;
  HOST_WIDE_INT s1h, 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 (unsigned HOST_WIDE_INT l1, HOST_WIDE_INT h1,
                HOST_WIDE_INT count, unsigned int prec,
                unsigned HOST_WIDE_INT *lv, HOST_WIDE_INT *hv)
{
  unsigned HOST_WIDE_INT s1l, s2l;
  HOST_WIDE_INT s1h, 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;
}
\f
/* 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 an integer.
   Return nonzero if the operation overflows.
   UNS nonzero says do unsigned division.  */

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

  memset (quo, 0, sizeof quo);

  memset (num, 0, sizeof num);  /* to zero 9th element */
  memset (den, 0, sizeof den);

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

  /* Special code for when the divisor < BASE.  */
  if (hden == 0 && lden < (unsigned HOST_WIDE_INT) BASE)
    {
      /* hnum != 0 already checked.  */
      for (i = 4 - 1; i >= 0; i--)
        {
          work = num[i] + carry * BASE;
          quo[i] = work / lden;
          carry = work % 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 nonzero 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] < (HOST_WIDE_INT) 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 */
      {
        unsigned HOST_WIDE_INT labs_rem = *lrem;
        HOST_WIDE_INT habs_rem = *hrem;
        unsigned HOST_WIDE_INT labs_den = lden, ltwice;
        HOST_WIDE_INT habs_den = hden, 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)
                && (labs_den < 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;
}
\f
/* Return true if built-in mathematical function specified by CODE
   preserves the sign of it argument, i.e. -f(x) == f(-x).  */

static bool
negate_mathfn_p (enum built_in_function code)
{
  switch (code)
    {
    case BUILT_IN_ASIN:
    case BUILT_IN_ASINF:
    case BUILT_IN_ASINL:
    case BUILT_IN_ATAN:
    case BUILT_IN_ATANF:
    case BUILT_IN_ATANL:
    case BUILT_IN_SIN:
    case BUILT_IN_SINF:
    case BUILT_IN_SINL:
    case BUILT_IN_TAN:
    case BUILT_IN_TANF:
    case BUILT_IN_TANL:
      return true;

    default:
      break;
    }
  return false;
}

/* Determine whether an expression T can be cheaply negated using
   the function negate_expr.  */

static bool
negate_expr_p (tree t)
{
  unsigned HOST_WIDE_INT val;
  unsigned int prec;
  tree type;

  if (t == 0)
    return false;

  type = TREE_TYPE (t);

  STRIP_SIGN_NOPS (t);
  switch (TREE_CODE (t))
    {
    case INTEGER_CST:
      if (TYPE_UNSIGNED (type) || ! flag_trapv)
        return true;

      /* Check that -CST will not overflow type.  */
      prec = TYPE_PRECISION (type);
      if (prec > HOST_BITS_PER_WIDE_INT)
        {
          if (TREE_INT_CST_LOW (t) != 0)
            return true;
          prec -= HOST_BITS_PER_WIDE_INT;
          val = TREE_INT_CST_HIGH (t);
        }
      else
        val = TREE_INT_CST_LOW (t);
      if (prec < HOST_BITS_PER_WIDE_INT)
        val &= ((unsigned HOST_WIDE_INT) 1 << prec) - 1;
      return val != ((unsigned HOST_WIDE_INT) 1 << (prec - 1));

    case REAL_CST:
    case NEGATE_EXPR:
      return true;

    case COMPLEX_CST:
      return negate_expr_p (TREE_REALPART (t))
             && negate_expr_p (TREE_IMAGPART (t));

    case PLUS_EXPR:
      if (FLOAT_TYPE_P (type) && !flag_unsafe_math_optimizations)
        return false;
      /* -(A + B) -> (-B) - A.  */
      if (negate_expr_p (TREE_OPERAND (t, 1))
          && reorder_operands_p (TREE_OPERAND (t, 0),
                                 TREE_OPERAND (t, 1)))
        return true;
      /* -(A + B) -> (-A) - B.  */
      return negate_expr_p (TREE_OPERAND (t, 0));

    case MINUS_EXPR:
      /* We can't turn -(A-B) into B-A when we honor signed zeros.  */
      return (! FLOAT_TYPE_P (type) || flag_unsafe_math_optimizations)
             && reorder_operands_p (TREE_OPERAND (t, 0),
                                    TREE_OPERAND (t, 1));

    case MULT_EXPR:
      if (TYPE_UNSIGNED (TREE_TYPE (t)))
        break;

      /* Fall through.  */

    case RDIV_EXPR:
      if (! HONOR_SIGN_DEPENDENT_ROUNDING (TYPE_MODE (TREE_TYPE (t))))
        return negate_expr_p (TREE_OPERAND (t, 1))
               || negate_expr_p (TREE_OPERAND (t, 0));
      break;

    case NOP_EXPR:
      /* Negate -((double)float) as (double)(-float).  */
      if (TREE_CODE (type) == REAL_TYPE)
        {
          tree tem = strip_float_extensions (t);
          if (tem != t)
            return negate_expr_p (tem);
        }
      break;

    case CALL_EXPR:
      /* Negate -f(x) as f(-x).  */
      if (negate_mathfn_p (builtin_mathfn_code (t)))
        return negate_expr_p (TREE_VALUE (TREE_OPERAND (t, 1)));
      break;

    case RSHIFT_EXPR:
      /* Optimize -((int)x >> 31) into (unsigned)x >> 31.  */
      if (TREE_CODE (TREE_OPERAND (t, 1)) == INTEGER_CST)
        {
          tree op1 = TREE_OPERAND (t, 1);
          if (TREE_INT_CST_HIGH (op1) == 0
              && (unsigned HOST_WIDE_INT) (TYPE_PRECISION (type) - 1)
                 == TREE_INT_CST_LOW (op1))
            return true;
        }
      break;

    default:
      break;
    }
  return false;
}

/* Given T, an expression, return the negation of T.  Allow for T to be
   null, in which case return null.  */

static tree
negate_expr (tree t)
{
  tree type;
  tree tem;

  if (t == 0)
    return 0;

  type = TREE_TYPE (t);
  STRIP_SIGN_NOPS (t);

  switch (TREE_CODE (t))
    {
    case INTEGER_CST:
      tem = fold_negate_const (t, type);
      if (! TREE_OVERFLOW (tem)
          || TYPE_UNSIGNED (type)
          || ! flag_trapv)
        return tem;
      break;

    case REAL_CST:
      tem = fold_negate_const (t, type);
      /* Two's complement FP formats, such as c4x, may overflow.  */
      if (! TREE_OVERFLOW (tem) || ! flag_trapping_math)
        return fold_convert (type, tem);
      break;

    case COMPLEX_CST:
      {
        tree rpart = negate_expr (TREE_REALPART (t));
        tree ipart = negate_expr (TREE_IMAGPART (t));

        if ((TREE_CODE (rpart) == REAL_CST
             && TREE_CODE (ipart) == REAL_CST)
            || (TREE_CODE (rpart) == INTEGER_CST
                && TREE_CODE (ipart) == INTEGER_CST))
          return build_complex (type, rpart, ipart);
      }
      break;

    case NEGATE_EXPR:
      return fold_convert (type, TREE_OPERAND (t, 0));

    case PLUS_EXPR:
      if (! FLOAT_TYPE_P (type) || flag_unsafe_math_optimizations)
        {
          /* -(A + B) -> (-B) - A.  */
          if (negate_expr_p (TREE_OPERAND (t, 1))
              && reorder_operands_p (TREE_OPERAND (t, 0),
                                     TREE_OPERAND (t, 1)))
            return fold_convert (type,
                                 fold (build (MINUS_EXPR, TREE_TYPE (t),
                                              negate_expr (TREE_OPERAND (t, 1)),
                                              TREE_OPERAND (t, 0))));
          /* -(A + B) -> (-A) - B.  */
          if (negate_expr_p (TREE_OPERAND (t, 0)))
            return fold_convert (type,
                                 fold (build (MINUS_EXPR, TREE_TYPE (t),
                                              negate_expr (TREE_OPERAND (t, 0)),
                                              TREE_OPERAND (t, 1))));
        }
      break;

    case MINUS_EXPR:
      /* - (A - B) -> B - A  */
      if ((! FLOAT_TYPE_P (type) || flag_unsafe_math_optimizations)
          && reorder_operands_p (TREE_OPERAND (t, 0), TREE_OPERAND (t, 1)))
        return fold_convert (type,
                             fold (build (MINUS_EXPR, TREE_TYPE (t),
                                          TREE_OPERAND (t, 1),
                                          TREE_OPERAND (t, 0))));
      break;

    case MULT_EXPR:
      if (TYPE_UNSIGNED (TREE_TYPE (t)))
        break;

      /* Fall through.  */

    case RDIV_EXPR:
      if (! HONOR_SIGN_DEPENDENT_ROUNDING (TYPE_MODE (TREE_TYPE (t))))
        {
          tem = TREE_OPERAND (t, 1);
          if (negate_expr_p (tem))
            return fold_convert (type,
                                 fold (build (TREE_CODE (t), TREE_TYPE (t),
                                              TREE_OPERAND (t, 0),
                                              negate_expr (tem))));
          tem = TREE_OPERAND (t, 0);
          if (negate_expr_p (tem))
            return fold_convert (type,
                                 fold (build (TREE_CODE (t), TREE_TYPE (t),
                                              negate_expr (tem),
                                              TREE_OPERAND (t, 1))));
        }
      break;

    case NOP_EXPR:
      /* Convert -((double)float) into (double)(-float).  */
      if (TREE_CODE (type) == REAL_TYPE)
        {
          tem = strip_float_extensions (t);
          if (tem != t && negate_expr_p (tem))
            return fold_convert (type, negate_expr (tem));
        }
      break;

    case CALL_EXPR:
      /* Negate -f(x) as f(-x).  */
      if (negate_mathfn_p (builtin_mathfn_code (t))
          && negate_expr_p (TREE_VALUE (TREE_OPERAND (t, 1))))
        {
          tree fndecl, arg, arglist;

          fndecl = get_callee_fndecl (t);
          arg = negate_expr (TREE_VALUE (TREE_OPERAND (t, 1)));
          arglist = build_tree_list (NULL_TREE, arg);
          return build_function_call_expr (fndecl, arglist);
        }
      break;

    case RSHIFT_EXPR:
      /* Optimize -((int)x >> 31) into (unsigned)x >> 31.  */
      if (TREE_CODE (TREE_OPERAND (t, 1)) == INTEGER_CST)
        {
          tree op1 = TREE_OPERAND (t, 1);
          if (TREE_INT_CST_HIGH (op1) == 0
              && (unsigned HOST_WIDE_INT) (TYPE_PRECISION (type) - 1)
                 == TREE_INT_CST_LOW (op1))
            {
              tree ntype = TYPE_UNSIGNED (type)
                           ? lang_hooks.types.signed_type (type)
                           : lang_hooks.types.unsigned_type (type);
              tree temp = fold_convert (ntype, TREE_OPERAND (t, 0));
              temp = fold (build2 (RSHIFT_EXPR, ntype, temp, op1));
              return fold_convert (type, temp);
            }
        }
      break;

    default:
      break;
    }

  tem = fold (build1 (NEGATE_EXPR, TREE_TYPE (t), t));
  return fold_convert (type, tem);
}
\f
/* Split a tree IN into a constant, literal and variable parts that could be
   combined with CODE to make IN.  "constant" means an expression with
   TREE_CONSTANT but that isn't an actual constant.  CODE must be a
   commutative arithmetic operation.  Store the constant part into *CONP,
   the literal in *LITP and return the variable part.  If a part isn't
   present, set it to null.  If the tree does not decompose in this way,
   return the entire tree as the variable part and the other parts as null.

   If CODE is PLUS_EXPR we also split trees that use MINUS_EXPR.  In that
   case, we negate an operand that was subtracted.  Except if it is a
   literal for which we use *MINUS_LITP instead.

   If NEGATE_P is true, we are negating all of IN, again except a literal
   for which we use *MINUS_LITP instead.

   If IN is itself a literal or constant, return it as appropriate.

   Note that we do not guarantee that any of the three values will be the
   same type as IN, but they will have the same signedness and mode.  */

static tree
split_tree (tree in, enum tree_code code, tree *conp, tree *litp,
            tree *minus_litp, int negate_p)
{
  tree var = 0;

  *conp = 0;
  *litp = 0;
  *minus_litp = 0;

  /* Strip any conversions that don't change the machine mode or signedness.  */
  STRIP_SIGN_NOPS (in);

  if (TREE_CODE (in) == INTEGER_CST || TREE_CODE (in) == REAL_CST)
    *litp = in;
  else 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))))
    {
      tree op0 = TREE_OPERAND (in, 0);
      tree op1 = TREE_OPERAND (in, 1);
      int neg1_p = TREE_CODE (in) == MINUS_EXPR;
      int neg_litp_p = 0, neg_conp_p = 0, neg_var_p = 0;

      /* First see if either of the operands is a literal, then a constant.  */
      if (TREE_CODE (op0) == INTEGER_CST || TREE_CODE (op0) == REAL_CST)
        *litp = op0, op0 = 0;
      else if (TREE_CODE (op1) == INTEGER_CST || TREE_CODE (op1) == REAL_CST)
        *litp = op1, neg_litp_p = neg1_p, op1 = 0;

      if (op0 != 0 && TREE_CONSTANT (op0))
        *conp = op0, op0 = 0;
      else if (op1 != 0 && TREE_CONSTANT (op1))
        *conp = op1, neg_conp_p = neg1_p, op1 = 0;

      /* If we haven't dealt with either operand, this is not a case we can
         decompose.  Otherwise, VAR is either of the ones remaining, if any.  */
      if (op0 != 0 && op1 != 0)
        var = in;
      else if (op0 != 0)
        var = op0;
      else
        var = op1, neg_var_p = neg1_p;

      /* Now do any needed negations.  */
      if (neg_litp_p)
        *minus_litp = *litp, *litp = 0;
      if (neg_conp_p)
        *conp = negate_expr (*conp);
      if (neg_var_p)
        var = negate_expr (var);
    }
  else if (TREE_CONSTANT (in))
    *conp = in;
  else
    var = in;

  if (negate_p)
    {
      if (*litp)
        *minus_litp = *litp, *litp = 0;
      else if (*minus_litp)
        *litp = *minus_litp, *minus_litp = 0;
      *conp = negate_expr (*conp);
      var = negate_expr (var);
    }

  return var;
}

/* Re-associate trees split by the above function.  T1 and T2 are either
   expressions to associate or null.  Return the new expression, if any.  If
   we build an operation, do it in TYPE and with CODE.  */

static tree
associate_trees (tree t1, tree t2, enum tree_code code, tree type)
{
  if (t1 == 0)
    return t2;
  else if (t2 == 0)
    return t1;

  /* If either input is CODE, a PLUS_EXPR, or a MINUS_EXPR, don't
     try to fold this since we will have infinite recursion.  But do
     deal with any NEGATE_EXPRs.  */
  if (TREE_CODE (t1) == code || TREE_CODE (t2) == code
      || TREE_CODE (t1) == MINUS_EXPR || TREE_CODE (t2) == MINUS_EXPR)
    {
      if (code == PLUS_EXPR)
        {
          if (TREE_CODE (t1) == NEGATE_EXPR)
            return build (MINUS_EXPR, type, fold_convert (type, t2),
                          fold_convert (type, TREE_OPERAND (t1, 0)));
          else if (TREE_CODE (t2) == NEGATE_EXPR)
            return build (MINUS_EXPR, type, fold_convert (type, t1),
                          fold_convert (type, TREE_OPERAND (t2, 0)));
        }
      return build (code, type, fold_convert (type, t1),
                    fold_convert (type, t2));
    }

  return fold (build (code, type, fold_convert (type, t1),
                      fold_convert (type, t2)));
}
\f
/* 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.  */

static tree
int_const_binop (enum tree_code code, tree arg1, tree arg2, int notrunc)
{
  unsigned HOST_WIDE_INT int1l, int2l;
  HOST_WIDE_INT int1h, int2h;
  unsigned HOST_WIDE_INT low;
  HOST_WIDE_INT hi;
  unsigned HOST_WIDE_INT garbagel;
  HOST_WIDE_INT garbageh;
  tree t;
  tree type = TREE_TYPE (arg1);
  int uns = TYPE_UNSIGNED (type);
  int is_sizetype
    = (TREE_CODE (type) == INTEGER_TYPE && TYPE_IS_SIZETYPE (type));
  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 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 (type),
                     &low, &hi, !uns);
      no_overflow = 1;
      break;

    case RROTATE_EXPR:
      int2l = - int2l;
    case LROTATE_EXPR:
      lrotate_double (int1l, int1h, int2l, TYPE_PRECISION (type),
                      &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 && (HOST_WIDE_INT) int2l > 0
          && ! TREE_CONSTANT_OVERFLOW (arg1)
          && ! TREE_CONSTANT_OVERFLOW (arg2)
          && int1h == 0 && (HOST_WIDE_INT) 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 && (HOST_WIDE_INT) int2l > 0
          && ! TREE_CONSTANT_OVERFLOW (arg1)
          && ! TREE_CONSTANT_OVERFLOW (arg2)
          && int1h == 0 && (HOST_WIDE_INT) 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)
                   && int1l < int2l));
      else
        low = (int1h < int2h
               || (int1h == int2h && int1l < int2l));

      if (low == (code == MIN_EXPR))
        low = int1l, hi = int1h;
      else
        low = int2l, hi = int2h;
      break;

    default:
      abort ();
    }

  /* If this is for a sizetype, can be represented as one (signed)
     HOST_WIDE_INT word, and doesn't overflow, use size_int since it caches
     constants.  */
  if (is_sizetype
      && ((hi == 0 && (HOST_WIDE_INT) low >= 0)
          || (hi == -1 && (HOST_WIDE_INT) low < 0))
      && overflow == 0 && ! TREE_OVERFLOW (arg1) && ! TREE_OVERFLOW (arg2))
    return size_int_type_wide (low, type);
  else
    {
      t = build_int_2 (low, hi);
      TREE_TYPE (t) = TREE_TYPE (arg1);
    }

  TREE_OVERFLOW (t)
    = ((notrunc
        ? (!uns || is_sizetype) && overflow
        : (force_fit_type (t, (!uns || is_sizetype) && 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 (is_sizetype
      && ! 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 (enum tree_code code, tree arg1, tree arg2, int notrunc)
{
  STRIP_NOPS (arg1);
  STRIP_NOPS (arg2);

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

  if (TREE_CODE (arg1) == REAL_CST)
    {
      enum machine_mode mode;
      REAL_VALUE_TYPE d1;
      REAL_VALUE_TYPE d2;
      REAL_VALUE_TYPE value;
      tree t, type;

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

      type = TREE_TYPE (arg1);
      mode = TYPE_MODE (type);

      /* Don't perform operation if we honor signaling NaNs and
         either operand is a NaN.  */
      if (HONOR_SNANS (mode)
          && (REAL_VALUE_ISNAN (d1) || REAL_VALUE_ISNAN (d2)))
        return NULL_TREE;

      /* Don't perform operation if it would raise a division
         by zero exception.  */
      if (code == RDIV_EXPR
          && REAL_VALUES_EQUAL (d2, dconst0)
          && (flag_trapping_math || ! MODE_HAS_INFINITIES (mode)))
        return NULL_TREE;

      /* 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;

      REAL_ARITHMETIC (value, code, d1, d2);

      t = build_real (type, real_value_truncate (mode, value));

      TREE_OVERFLOW (t)
        = (force_fit_type (t, 0)
           | TREE_OVERFLOW (arg1) | TREE_OVERFLOW (arg2));
      TREE_CONSTANT_OVERFLOW (t)
        = TREE_OVERFLOW (t)
          | TREE_CONSTANT_OVERFLOW (arg1)
          | TREE_CONSTANT_OVERFLOW (arg2);
      return t;
    }
  if (TREE_CODE (arg1) == COMPLEX_CST)
    {
      tree type = TREE_TYPE (arg1);
      tree r1 = TREE_REALPART (arg1);
      tree i1 = TREE_IMAGPART (arg1);
      tree r2 = TREE_REALPART (arg2);
      tree i2 = TREE_IMAGPART (arg2);
      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:
          {
            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;
}

/* These are the hash table functions for the hash table of INTEGER_CST
   nodes of a sizetype.  */

/* Return the hash code code X, an INTEGER_CST.  */

static hashval_t
size_htab_hash (const void *x)
{
  tree t = (tree) x;

  return (TREE_INT_CST_HIGH (t) ^ TREE_INT_CST_LOW (t)
          ^ htab_hash_pointer (TREE_TYPE (t))
          ^ (TREE_OVERFLOW (t) << 20));
}

/* Return nonzero if the value represented by *X (an INTEGER_CST tree node)
   is the same as that given by *Y, which is the same.  */

static int
size_htab_eq (const void *x, const void *y)
{
  tree xt = (tree) x;
  tree yt = (tree) y;

  return (TREE_INT_CST_HIGH (xt) == TREE_INT_CST_HIGH (yt)
          && TREE_INT_CST_LOW (xt) == TREE_INT_CST_LOW (yt)
          && TREE_TYPE (xt) == TREE_TYPE (yt)
          && TREE_OVERFLOW (xt) == TREE_OVERFLOW (yt));
}
\f
/* Return an INTEGER_CST with value whose low-order HOST_BITS_PER_WIDE_INT
   bits are given by NUMBER and of the sizetype represented by KIND.  */

tree
size_int_wide (HOST_WIDE_INT number, enum size_type_kind kind)
{
  return size_int_type_wide (number, sizetype_tab[(int) kind]);
}

/* Likewise, but the desired type is specified explicitly.  */

static GTY (()) tree new_const;
static GTY ((if_marked ("ggc_marked_p"), param_is (union tree_node)))
     htab_t size_htab;

tree
size_int_type_wide (HOST_WIDE_INT number, tree type)
{
  void **slot;

  if (size_htab == 0)
    {
      size_htab = htab_create_ggc (1024, size_htab_hash, size_htab_eq, NULL);
      new_const = make_node (INTEGER_CST);
    }

  /* Adjust NEW_CONST to be the constant we want.  If it's already in the
     hash table, we return the value from the hash table.  Otherwise, we
     place that in the hash table and make a new node for the next time.  */
  TREE_INT_CST_LOW (new_const) = number;
  TREE_INT_CST_HIGH (new_const) = number < 0 ? -1 : 0;
  TREE_TYPE (new_const) = type;
  TREE_OVERFLOW (new_const) = TREE_CONSTANT_OVERFLOW (new_const)
    = force_fit_type (new_const, 0);

  slot = htab_find_slot (size_htab, new_const, INSERT);
  if (*slot == 0)
    {
      tree t = new_const;

      *slot = new_const;
      new_const = make_node (INTEGER_CST);
      return t;
    }
  else
    return (tree) *slot;
}

/* Combine operands OP1 and OP2 with arithmetic operation CODE.  CODE
   is a tree code.  The type of the result is taken from the operands.
   Both must be the same type integer type and it must be a size type.
   If the operands are constant, so is the result.  */

tree
size_binop (enum tree_code code, tree arg0, tree arg1)
{
  tree type = TREE_TYPE (arg0);

  if (TREE_CODE (type) != INTEGER_TYPE || ! TYPE_IS_SIZETYPE (type)
      || type != TREE_TYPE (arg1))
    abort ();

  /* 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);
    }

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

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

/* Given two values, either both of sizetype or both of bitsizetype,
   compute the difference between the two values.  Return the value
   in signed type corresponding to the type of the operands.  */

tree
size_diffop (tree arg0, tree arg1)
{
  tree type = TREE_TYPE (arg0);
  tree ctype;

  if (TREE_CODE (type) != INTEGER_TYPE || ! TYPE_IS_SIZETYPE (type)
      || type != TREE_TYPE (arg1))
    abort ();

  /* If the type is already signed, just do the simple thing.  */
  if (!TYPE_UNSIGNED (type))
    return size_binop (MINUS_EXPR, arg0, arg1);

  ctype = (type == bitsizetype || type == ubitsizetype
           ? sbitsizetype : ssizetype);

  /* If either operand is not a constant, do the conversions to the signed
     type and subtract.  The hardware will do the right thing with any
     overflow in the subtraction.  */
  if (TREE_CODE (arg0) != INTEGER_CST || TREE_CODE (arg1) != INTEGER_CST)
    return size_binop (MINUS_EXPR, fold_convert (ctype, arg0),
                       fold_convert (ctype, arg1));

  /* If ARG0 is larger than ARG1, subtract and return the result in CTYPE.
     Otherwise, subtract the other way, convert to CTYPE (we know that can't
     overflow) and negate (which can't either).  Special-case a result
     of zero while we're here.  */
  if (tree_int_cst_equal (arg0, arg1))
    return fold_convert (ctype, integer_zero_node);
  else if (tree_int_cst_lt (arg1, arg0))
    return fold_convert (ctype, size_binop (MINUS_EXPR, arg0, arg1));
  else
    return size_binop (MINUS_EXPR, fold_convert (ctype, integer_zero_node),
                       fold_convert (ctype, size_binop (MINUS_EXPR,
                                                        arg1, arg0)));
}
\f

/* Attempt to fold type conversion operation CODE of expression ARG1 to
   type TYPE.  If no simplification can be done return NULL_TREE.  */

static tree
fold_convert_const (enum tree_code code, tree type, tree arg1)
{
  int overflow = 0;
  tree t;

  if (TREE_TYPE (arg1) == type)
    return arg1;

  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 NULL_TREE;

          /* If we are trying to make a sizetype for a small integer, use
             size_int to pick up cached types to reduce duplicate nodes.  */
          if (TREE_CODE (type) == INTEGER_TYPE && TYPE_IS_SIZETYPE (type)
              && !TREE_CONSTANT_OVERFLOW (arg1)
              && compare_tree_int (arg1, 10000) < 0)
            return size_int_type_wide (TREE_INT_CST_LOW (arg1), type);

          /* 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
                                 && (TYPE_UNSIGNED (type)
                                    < TYPE_UNSIGNED (TREE_TYPE (arg1)))))
                && ! POINTER_TYPE_P (TREE_TYPE (arg1)))
               || TREE_OVERFLOW (arg1));
          TREE_CONSTANT_OVERFLOW (t)
            = TREE_OVERFLOW (t) | TREE_CONSTANT_OVERFLOW (arg1);
          return t;
        }
      else if (TREE_CODE (arg1) == REAL_CST)
        {
          /* The following code implements the floating point to integer
             conversion rules required by the Java Language Specification,
             that IEEE NaNs are mapped to zero and values that overflow
             the target precision saturate, i.e. values greater than
             INT_MAX are mapped to INT_MAX, and values less than INT_MIN
             are mapped to INT_MIN.  These semantics are allowed by the
             C and C++ standards that simply state that the behavior of
             FP-to-integer conversion is unspecified upon overflow.  */

          HOST_WIDE_INT high, low;

          REAL_VALUE_TYPE r;
          REAL_VALUE_TYPE x = TREE_REAL_CST (arg1);

          switch (code)
            {
            case FIX_TRUNC_EXPR:
              real_trunc (&r, VOIDmode, &x);
              break;

            case FIX_CEIL_EXPR:
              real_ceil (&r, VOIDmode, &x);
              break;

            case FIX_FLOOR_EXPR:
              real_floor (&r, VOIDmode, &x);
              break;

            default:
              abort ();
            }

          /* If R is NaN, return zero and show we have an overflow.  */
          if (REAL_VALUE_ISNAN (r))
            {
              overflow = 1;
              high = 0;
              low = 0;
            }

          /* See if R is less than the lower bound or greater than the
             upper bound.  */

          if (! overflow)
            {
              tree lt = TYPE_MIN_VALUE (type);
              REAL_VALUE_TYPE l = real_value_from_int_cst (NULL_TREE, lt);
              if (REAL_VALUES_LESS (r, l))
                {
                  overflow = 1;
                  high = TREE_INT_CST_HIGH (lt);
                  low = TREE_INT_CST_LOW (lt);
                }
            }

          if (! overflow)
            {
              tree ut = TYPE_MAX_VALUE (type);
              if (ut)
                {
                  REAL_VALUE_TYPE u = real_value_from_int_cst (NULL_TREE, ut);
                  if (REAL_VALUES_LESS (u, r))
                    {
                      overflow = 1;
                      high = TREE_INT_CST_HIGH (ut);
                      low = TREE_INT_CST_LOW (ut);
                    }
                }
            }

          if (! overflow)
            REAL_VALUE_TO_INT (&low, &high, r);

          t = build_int_2 (low, high);
          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);
          return t;
        }
    }
  else if (TREE_CODE (type) == REAL_TYPE)
    {
      if (TREE_CODE (arg1) == INTEGER_CST)
        return build_real_from_int_cst (type, arg1);
      if (TREE_CODE (arg1) == REAL_CST)
        {
          if (REAL_VALUE_ISNAN (TREE_REAL_CST (arg1)))
            {
              /* We make a copy of ARG1 so that we don't modify an
                 existing constant tree.  */
              t = copy_node (arg1);
              TREE_TYPE (t) = type;
              return t;
            }

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

          TREE_OVERFLOW (t)
            = TREE_OVERFLOW (arg1) | force_fit_type (t, 0);
          TREE_CONSTANT_OVERFLOW (t)
            = TREE_OVERFLOW (t) | TREE_CONSTANT_OVERFLOW (arg1);
          return t;
        }
    }
  return NULL_TREE;
}

/* Convert expression ARG to type TYPE.  Used by the middle-end for
   simple conversions in preference to calling the front-end's convert.  */

static tree
fold_convert (tree type, tree arg)
{
  tree orig = TREE_TYPE (arg);
  tree tem;

  if (type == orig)
    return arg;

  if (TREE_CODE (arg) == ERROR_MARK
      || TREE_CODE (type) == ERROR_MARK
      || TREE_CODE (orig) == ERROR_MARK)
    return error_mark_node;

  if (TYPE_MAIN_VARIANT (type) == TYPE_MAIN_VARIANT (orig))
    return fold (build1 (NOP_EXPR, type, arg));

  if (INTEGRAL_TYPE_P (type) || POINTER_TYPE_P (type))
    {
      if (TREE_CODE (arg) == INTEGER_CST)
        {
          tem = fold_convert_const (NOP_EXPR, type, arg);
          if (tem != NULL_TREE)
            return tem;
        }
      if (INTEGRAL_TYPE_P (orig) || POINTER_TYPE_P (orig))
        return fold (build1 (NOP_EXPR, type, arg));
      if (TREE_CODE (orig) == COMPLEX_TYPE)
        {
          tem = fold (build1 (REALPART_EXPR, TREE_TYPE (orig), arg));
          return fold_convert (type, tem);
        }
      if (TREE_CODE (orig) == VECTOR_TYPE
          && GET_MODE_SIZE (TYPE_MODE (type))
             == GET_MODE_SIZE (TYPE_MODE (orig)))
        return fold (build1 (NOP_EXPR, type, arg));
    }
  else if (TREE_CODE (type) == REAL_TYPE)
    {
      if (TREE_CODE (arg) == INTEGER_CST)
        {
          tem = fold_convert_const (FLOAT_EXPR, type, arg);
          if (tem != NULL_TREE)
            return tem;
        }
      else if (TREE_CODE (arg) == REAL_CST)
        {
          tem = fold_convert_const (NOP_EXPR, type, arg);
          if (tem != NULL_TREE)
            return tem;
        }

      if (INTEGRAL_TYPE_P (orig) || POINTER_TYPE_P (orig))
        return fold (build1 (FLOAT_EXPR, type, arg));
      if (TREE_CODE (orig) == REAL_TYPE)
        return fold (build1 (flag_float_store ? CONVERT_EXPR : NOP_EXPR,
                             type, arg));
      if (TREE_CODE (orig) == COMPLEX_TYPE)
        {
          tem = fold (build1 (REALPART_EXPR, TREE_TYPE (orig), arg));
          return fold_convert (type, tem);
        }
    }
  else if (TREE_CODE (type) == COMPLEX_TYPE)
    {
      if (INTEGRAL_TYPE_P (orig)
          || POINTER_TYPE_P (orig)
          || TREE_CODE (orig) == REAL_TYPE)
        return build (COMPLEX_EXPR, type,
                      fold_convert (TREE_TYPE (type), arg),
                      fold_convert (TREE_TYPE (type), integer_zero_node));
      if (TREE_CODE (orig) == COMPLEX_TYPE)
        {
          tree rpart, ipart;

          if (TREE_CODE (arg) == COMPLEX_EXPR)
            {
              rpart = fold_convert (TREE_TYPE (type), TREE_OPERAND (arg, 0));
              ipart = fold_convert (TREE_TYPE (type), TREE_OPERAND (arg, 1));
              return fold (build (COMPLEX_EXPR, type, rpart, ipart));
            }

          arg = save_expr (arg);
          rpart = fold (build1 (REALPART_EXPR, TREE_TYPE (orig), arg));
          ipart = fold (build1 (IMAGPART_EXPR, TREE_TYPE (orig), arg));
          rpart = fold_convert (TREE_TYPE (type), rpart);
          ipart = fold_convert (TREE_TYPE (type), ipart);
          return fold (build (COMPLEX_EXPR, type, rpart, ipart));
        }
    }
  else if (TREE_CODE (type) == VECTOR_TYPE)
    {
      if ((INTEGRAL_TYPE_P (orig) || POINTER_TYPE_P (orig))
          && GET_MODE_SIZE (TYPE_MODE (type))
             == GET_MODE_SIZE (TYPE_MODE (orig)))
        return fold (build1 (NOP_EXPR, type, arg));
      if (TREE_CODE (orig) == VECTOR_TYPE
          && GET_MODE_SIZE (TYPE_MODE (type))
             == GET_MODE_SIZE (TYPE_MODE (orig)))
        return fold (build1 (NOP_EXPR, type, arg));
    }
  else if (VOID_TYPE_P (type))
    return fold (build1 (CONVERT_EXPR, type, arg));
  abort ();
}
\f
/* Return an expr equal to X but certainly not valid as an lvalue.  */

tree
non_lvalue (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)
    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 (tree x)
{
  if (pedantic_lvalues)
    return non_lvalue (x);
  else
    return x;
}
\f
/* 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 (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 (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 ();
    }
}


/* Convert a comparison tree code from an enum tree_code representation
   into a compcode bit-based encoding.  This function is the inverse of
   compcode_to_comparison.  */

static int
comparison_to_compcode (enum tree_code code)
{
  switch (code)
    {
    case LT_EXPR:
      return COMPCODE_LT;
    case EQ_EXPR:
      return COMPCODE_EQ;
    case LE_EXPR:
      return COMPCODE_LE;
    case GT_EXPR:
      return COMPCODE_GT;
    case NE_EXPR:
      return COMPCODE_NE;
    case GE_EXPR:
      return COMPCODE_GE;
    default:
      abort ();
    }
}

/* Convert a compcode bit-based encoding of a comparison operator back
   to GCC's enum tree_code representation.  This function is the
   inverse of comparison_to_compcode.  */

static enum tree_code
compcode_to_comparison (int code)
{
  switch (code)
    {
    case COMPCODE_LT:
      return LT_EXPR;
    case COMPCODE_EQ:
      return EQ_EXPR;
    case COMPCODE_LE:
      return LE_EXPR;
    case COMPCODE_GT:
      return GT_EXPR;
    case COMPCODE_NE:
      return NE_EXPR;
    case COMPCODE_GE:
      return GE_EXPR;
    default:
      abort ();
    }
}

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

static int
truth_value_p (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);
}
\f
/* Return nonzero if two operands (typically of the same tree node)
   are necessarily equal.  If either argument has side-effects this
   function returns zero.

   If ONLY_CONST is nonzero, only return nonzero 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.

   If ONLY_CONST is zero, a VAR_DECL is considered equal to itself
   even though it may hold multiple values during a function.
   This is because a GCC tree node guarantees that nothing else is
   executed between the evaluation of its "operands" (which may often
   be evaluated in arbitrary order).  Hence if the operands themselves
   don't side-effect, the VAR_DECLs, PARM_DECLs etc... must hold the
   same value in each operand/subexpression.  Hence a zero value for
   ONLY_CONST assumes isochronic (or instantaneous) tree equivalence.
   If comparing arbitrary expression trees, such as from different
   statements, ONLY_CONST must usually be nonzero.  */

int
operand_equal_p (tree arg0, tree arg1, int only_const)
{
  tree fndecl;

  /* If either is ERROR_MARK, they aren't equal.  */
  if (TREE_CODE (arg0) == ERROR_MARK || TREE_CODE (arg1) == ERROR_MARK)
    return 0;

  /* 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 (TYPE_UNSIGNED (TREE_TYPE (arg0)) != TYPE_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.  */
      || TREE_CODE (TREE_TYPE (arg0)) == ERROR_MARK
      || TREE_CODE (TREE_TYPE (arg1)) == ERROR_MARK
      || 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_equal (arg0, 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 VECTOR_CST:
        {
          tree v1, v2;

          if (TREE_CONSTANT_OVERFLOW (arg0)
              || TREE_CONSTANT_OVERFLOW (arg1))
            return 0;

          v1 = TREE_VECTOR_CST_ELTS (arg0);
          v2 = TREE_VECTOR_CST_ELTS (arg1);
          while (v1 && v2)
            {
              if (!operand_equal_p (TREE_VALUE (v1), TREE_VALUE (v2),
                                    only_const))
                return 0;
              v1 = TREE_CHAIN (v1);
              v2 = TREE_CHAIN (v2);
            }

          return 1;
        }

      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)
                && ! memcmp (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)
          && (TYPE_UNSIGNED (TREE_TYPE (arg0))
              != TYPE_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 (commutative_tree_code (TREE_CODE (arg0))
              && 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':
      /* If either of the pointer (or reference) expressions we are
         dereferencing contain a side effect, these cannot be equal.  */
      if (TREE_SIDE_EFFECTS (arg0)
          || TREE_SIDE_EFFECTS (arg1))
        return 0;

      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:
        case ARRAY_RANGE_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;
        }

    case 'e':
      switch (TREE_CODE (arg0))
        {
        case ADDR_EXPR:
        case TRUTH_NOT_EXPR:
          return operand_equal_p (TREE_OPERAND (arg0, 0),
                                  TREE_OPERAND (arg1, 0), 0);

        case RTL_EXPR:
          return rtx_equal_p (RTL_EXPR_RTL (arg0), RTL_EXPR_RTL (arg1));

        case CALL_EXPR:
          /* If the CALL_EXPRs call different functions, then they
             clearly can not be equal.  */
          if (! operand_equal_p (TREE_OPERAND (arg0, 0),
                                 TREE_OPERAND (arg1, 0), 0))
            return 0;

          /* Only consider const functions equivalent.  */
          fndecl = get_callee_fndecl (arg0);
          if (fndecl == NULL_TREE
              || ! (flags_from_decl_or_type (fndecl) & ECF_CONST))
            return 0;

          /* Now see if all the arguments are the same.  operand_equal_p
             does not handle TREE_LIST, so we walk the operands here
             feeding them to operand_equal_p.  */
          arg0 = TREE_OPERAND (arg0, 1);
          arg1 = TREE_OPERAND (arg1, 1);
          while (arg0 && arg1)
            {
              if (! operand_equal_p (TREE_VALUE (arg0), TREE_VALUE (arg1), 0))
                return 0;

              arg0 = TREE_CHAIN (arg0);
              arg1 = TREE_CHAIN (arg1);
            }

          /* If we get here and both argument lists are exhausted
             then the CALL_EXPRs are equal.  */
          return ! (arg0 || arg1);

        default:
          return 0;
        }

    case 'd':
        /* Consider __builtin_sqrt equal to sqrt.  */
        return TREE_CODE (arg0) == FUNCTION_DECL
               && DECL_BUILT_IN (arg0) && DECL_BUILT_IN (arg1)
               && DECL_BUILT_IN_CLASS (arg0) == DECL_BUILT_IN_CLASS (arg1)
               && DECL_FUNCTION_CODE (arg0) == DECL_FUNCTION_CODE (arg1);

    default:
      return 0;
    }
}
\f
/* 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 (tree arg0, tree arg1, tree other)
{
  int unsignedp1, unsignedpo;
  tree primarg0, primarg1, primother;
  unsigned int 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 = fold_convert (lang_hooks.types.signed_or_unsigned_type
                               (unsignedp1, TREE_TYPE (primarg1)), primarg1);

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

  return 0;
}
\f
/* 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 nonzero 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 (tree arg, tree *cval1, tree *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';

  else if (class == 'e' && code == SAVE_EXPR && SAVE_EXPR_RTL (arg) == 0
           && ! TREE_SIDE_EFFECTS (TREE_OPERAND (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;
    }

  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;
    }
}
\f
/* 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 (tree arg, tree old0, tree new0, tree old1, tree 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;
    }
}
\f
/* 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.  */

tree
omit_one_operand (tree type, tree result, tree omitted)
{
  tree t = fold_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 (tree type, tree result, tree omitted)
{
  tree t = fold_convert (type, result);

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

  return pedantic_non_lvalue (t);
}
\f
/* 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 (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)))
          && !flag_unsafe_math_optimizations
          && code != NE_EXPR
          && code != EQ_EXPR)
        return build1 (TRUTH_NOT_EXPR, type, arg);
      else if (code == UNORDERED_EXPR
               || code == ORDERED_EXPR
               || code == UNEQ_EXPR
               || code == UNLT_EXPR
               || code == UNLE_EXPR
               || code == UNGT_EXPR
               || code == UNGE_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 fold_convert (type, build_int_2 (integer_zerop (arg), 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,
                    fold_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 (enum tree_code code, tree type, tree arg0, tree 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))));
}
\f
/* 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 nonzero.  */

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

  BIT_FIELD_REF_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 (enum tree_code code, tree compare_type,
                            tree lhs, tree rhs)
{
  HOST_WIDE_INT lbitpos, lbitsize, rbitpos, rbitsize, nbitpos, nbitsize;
  tree type = TREE_TYPE (lhs);
  tree signed_type, unsigned_type;
  int const_p = TREE_CODE (rhs) == INTEGER_CST;
  enum machine_mode lmode, rmode, nmode;
  int lunsignedp, runsignedp;
  int lvolatilep = 0, rvolatilep = 0;
  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.  We also don't want to
     do anything if the inner expression is a PLACEHOLDER_EXPR since we
     then will no longer be able to replace it.  */
  linner = get_inner_reference (lhs, &lbitsize, &lbitpos, &offset, &lmode,
                                &lunsignedp, &lvolatilep);
  if (linner == lhs || lbitsize == GET_MODE_BITSIZE (lmode) || lbitsize < 0
      || offset != 0 || TREE_CODE (linner) == PLACEHOLDER_EXPR)
    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);

     if (rinner == rhs || lbitpos != rbitpos || lbitsize != rbitsize
         || lunsignedp != runsignedp || offset != 0
         || TREE_CODE (rinner) == PLACEHOLDER_EXPR)
       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.  */
  nmode = get_best_mode (lbitsize, lbitpos,
                         const_p ? TYPE_ALIGN (TREE_TYPE (linner))
                         : MIN (TYPE_ALIGN (TREE_TYPE (linner)),
                                TYPE_ALIGN (TREE_TYPE (rinner))),
                         word_mode, lvolatilep || rvolatilep);
  if (nmode == VOIDmode)
    return 0;

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

  /* 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.  */
  nbitsize = GET_MODE_BITSIZE (nmode);
  nbitpos = lbitpos & ~ (nbitsize - 1);
  lbitpos -= nbitpos;
  if (nbitsize == lbitsize)
    return 0;

  if (BYTES_BIG_ENDIAN)
    lbitpos = nbitsize - 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 = fold_convert (unsigned_type, mask);
  mask = const_binop (LSHIFT_EXPR, mask, size_int (nbitsize - lbitsize), 0);
  mask = const_binop (RSHIFT_EXPR, mask,
                      size_int (nbitsize - 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,
                                             nbitsize, nbitpos, 1),
                         mask),
                  build (BIT_AND_EXPR, unsigned_type,
                         make_bit_field_ref (rinner, unsigned_type,
                                             nbitsize, nbitpos, 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,
                                        fold_convert (unsigned_type, rhs),
                                        size_int (lbitsize), 0)))
        {
          warning ("comparison is always %d due to width of bit-field",
                   code == NE_EXPR);
          return fold_convert (compare_type,
                               (code == NE_EXPR
                                ? integer_one_node : integer_zero_node));
        }
    }
  else
    {
      tree tem = const_binop (RSHIFT_EXPR, fold_convert (signed_type, rhs),
                              size_int (lbitsize - 1), 0);
      if (! integer_zerop (tem) && ! integer_all_onesp (tem))
        {
          warning ("comparison is always %d due to width of bit-field",
                   code == NE_EXPR);
          return fold_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 = fold_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, nbitsize, nbitpos, 1);
  if (lvolatilep)
    {
      TREE_SIDE_EFFECTS (lhs) = 1;
      TREE_THIS_VOLATILE (lhs) = 1;
    }

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

  return build (code, compare_type,
                build (BIT_AND_EXPR, unsigned_type, lhs, mask),
                rhs);
}
\f
/* 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 (tree exp, HOST_WIDE_INT *pbitsize,
                        HOST_WIDE_INT *pbitpos, enum machine_mode *pmode,
                        int *punsignedp, int *pvolatilep,
                        tree *pmask, tree *pand_mask)
{
  tree outer_type = 0;
  tree and_mask = 0;
  tree mask, inner, offset;
  tree unsigned_type;
  unsigned int precision;

  /* 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;

  /* We are interested in the bare arrangement of bits, so strip everything
     that doesn't affect the machine mode.  However, record the type of the
     outermost expression if it may matter below.  */
  if (TREE_CODE (exp) == NOP_EXPR
      || TREE_CODE (exp) == CONVERT_EXPR
      || TREE_CODE (exp) == NON_LVALUE_EXPR)
    outer_type = TREE_TYPE (exp);
  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);
  if ((inner == exp && and_mask == 0)
      || *pbitsize < 0 || offset != 0
      || TREE_CODE (inner) == PLACEHOLDER_EXPR)
    return 0;

  /* If the number of bits in the reference is the same as the bitsize of
     the outer type, then the outer type gives the signedness. Otherwise
     (in case of a small bitfield) the signedness is unchanged.  */
  if (outer_type && *pbitsize == tree_low_cst (TYPE_SIZE (outer_type), 1))
    *punsignedp = TYPE_UNSIGNED (outer_type);

  /* Compute the mask to access the bitfield.  */
  unsigned_type = lang_hooks.types.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,
                        fold_convert (unsigned_type, and_mask), mask));

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

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

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

  tmask = build_int_2 (~0, ~0);
  TREE_TYPE (tmask) = lang_hooks.types.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: determine if VAL is the INTEGER_CONST that
   represents the sign bit of EXP's type.  If EXP represents a sign
   or zero extension, also test VAL against the unextended type.
   The return value is the (sub)expression whose sign bit is VAL,
   or NULL_TREE otherwise.  */

static tree
sign_bit_p (tree exp, tree val)
{
  unsigned HOST_WIDE_INT mask_lo, lo;
  HOST_WIDE_INT mask_hi, hi;
  int width;
  tree t;

  /* Tree EXP must have an integral type.  */
  t = TREE_TYPE (exp);
  if (! INTEGRAL_TYPE_P (t))
    return NULL_TREE;

  /* Tree VAL must be an integer constant.  */
  if (TREE_CODE (val) != INTEGER_CST
      || TREE_CONSTANT_OVERFLOW (val))
    return NULL_TREE;

  width = TYPE_PRECISION (t);
  if (width > HOST_BITS_PER_WIDE_INT)
    {
      hi = (unsigned HOST_WIDE_INT) 1 << (width - HOST_BITS_PER_WIDE_INT - 1);
      lo = 0;

      mask_hi = ((unsigned HOST_WIDE_INT) -1
                 >> (2 * HOST_BITS_PER_WIDE_INT - width));
      mask_lo = -1;
    }
  else
    {
      hi = 0;
      lo = (unsigned HOST_WIDE_INT) 1 << (width - 1);

      mask_hi = 0;
      mask_lo = ((unsigned HOST_WIDE_INT) -1
                 >> (HOST_BITS_PER_WIDE_INT - width));
    }

  /* We mask off those bits beyond TREE_TYPE (exp) so that we can
     treat VAL as if it were unsigned.  */
  if ((TREE_INT_CST_HIGH (val) & mask_hi) == hi
      && (TREE_INT_CST_LOW (val) & mask_lo) == lo)
    return exp;

  /* Handle extension from a narrower type.  */
  if (TREE_CODE (exp) == NOP_EXPR
      && TYPE_PRECISION (TREE_TYPE (TREE_OPERAND (exp, 0))) < width)
    return sign_bit_p (TREE_OPERAND (exp, 0), val);

  return NULL_TREE;
}

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

static int
simple_operand_p (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'
          || (DECL_P (exp)
              && ! 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))));
}
\f
/* 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 (enum tree_code code, tree type, tree arg0, int upper0_p,
             tree arg1, int 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, fold_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 fold_convert (type, result ? integer_one_node : integer_zero_node);
}
\f
/* 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 be made of 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 (tree exp, int *pin_p, tree *plow, tree *phigh)
{
  enum tree_code code;
  tree arg0 = NULL_TREE, arg1 = NULL_TREE, 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 = fold_convert (TREE_TYPE (exp), integer_zero_node);

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

      if (IS_EXPR_CODE_CLASS (TREE_CODE_CLASS (code)))
        {
          if (first_rtl_op (code) > 0)
            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 (code) > 1))
            arg1 = TREE_OPERAND (exp, 1);
        }

      /* Set ORIG_TYPE as soon as TYPE is non-null so that we do not
         lose a cast by accident.  */
      if (type != NULL_TREE && orig_type == NULL_TREE)
        orig_type = type;

      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 (TYPE_UNSIGNED (type) && (low == 0 || high == 0))
            {
              if (! merge_ranges (&n_in_p, &n_low, &n_high, in_p, low, high,
                                  1, fold_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, but we have a nonzero low
                 bound, reverse the range so it goes from zero to the low bound
                 minus 1.  */
              if (high == 0 && low && ! integer_zerop (low))
                {
                  in_p = ! in_p;
                  high = range_binop (MINUS_EXPR, NULL_TREE, low, 0,
                                      integer_one_node, 0);
                  low = fold_convert (type, integer_zero_node);
                }
            }
          continue;

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

              /* If the range is of the form +/- [ x+1, x ], we won't
                 be able to normalize it.  But then, it represents the
                 whole range or the empty set, so make it
                 +/- [ -, - ].  */
              if (tree_int_cst_equal (n_low, low)
                  && tree_int_cst_equal (n_high, high))
                low = high = 0;
              else
                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 (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 = fold_convert (type, n_low);

          if (n_high != 0)
            n_high = fold_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 (TYPE_UNSIGNED (type) && ! TYPE_UNSIGNED (TREE_TYPE (exp)))
            {
              tree equiv_type = lang_hooks.types.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) ? TYPE_MAX_VALUE (equiv_type)
                  : TYPE_MAX_VALUE (type);

              if (TYPE_PRECISION (type) == TYPE_PRECISION (TREE_TYPE (exp)))
                high_positive = fold (build (RSHIFT_EXPR, type,
                                             fold_convert (type,
                                                           high_positive),
                                             fold_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,
                                      fold_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,
                                      fold_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;
}
\f
/* 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 (tree type, tree exp, int in_p, tree low, tree high)
{
  tree etype = TREE_TYPE (exp);
  tree value;

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

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

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

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

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

  if (integer_zerop (low))
    {
      if (! TYPE_UNSIGNED (etype))
        {
          etype = lang_hooks.types.unsigned_type (etype);
          high = fold_convert (etype, high);
          exp = fold_convert (etype, exp);
        }
      return build_range_check (type, exp, 1, 0, high);
    }

  /* Optimize (c>=1) && (c<=127) into (signed char)c > 0.  */
  if (integer_onep (low) && TREE_CODE (high) == INTEGER_CST)
    {
      unsigned HOST_WIDE_INT lo;
      HOST_WIDE_INT hi;
      int prec;

      prec = TYPE_PRECISION (etype);
      if (prec <= HOST_BITS_PER_WIDE_INT)
        {
          hi = 0;
          lo = ((unsigned HOST_WIDE_INT) 1 << (prec - 1)) - 1;
        }
      else
        {
          hi = ((HOST_WIDE_INT) 1 << (prec - HOST_BITS_PER_WIDE_INT - 1)) - 1;
          lo = (unsigned HOST_WIDE_INT) -1;
        }

      if (TREE_INT_CST_HIGH (high) == hi && TREE_INT_CST_LOW (high) == lo)
        {
          if (TYPE_UNSIGNED (etype))
            {
              etype = lang_hooks.types.signed_type (etype);
              exp = fold_convert (etype, exp);
            }
          return fold (build (GT_EXPR, type, exp,
                              fold_convert (etype, integer_zero_node)));
        }
    }

  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, fold_convert (etype, integer_zero_node),
                              value);

  return 0;
}
\f
/* 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 (int *pin_p, tree *plow, tree *phigh, int in0_p, tree low0,
              tree high0, int in1_p, tree low1, tree 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 || highequal)
        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;
}
\f
#ifndef RANGE_TEST_NON_SHORT_CIRCUIT
#define RANGE_TEST_NON_SHORT_CIRCUIT (BRANCH_COST >= 2)
#endif

/* 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 (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 (RANGE_TEST_NON_SHORT_CIRCUIT
           && lhs != 0 && rhs != 0
           && (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 (lang_hooks.decls.global_bindings_p () == 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;
}
\f
/* 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 (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 (TYPE_UNSIGNED (type))
    temp = fold_convert (lang_hooks.types.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,
                        fold_convert (TREE_TYPE (c), mask), 0);
  /* If necessary, convert the type back to match the type of C.  */
  if (TYPE_UNSIGNED (type))
    temp = fold_convert (type, temp);

  return fold_convert (type, const_binop (BIT_XOR_EXPR, c, temp, 0));
}
\f
/* 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 (enum tree_code code, tree truth_type, tree lhs, tree rhs)
{
  /* If this is the "or" of two comparisons, we can do something if
     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;
  HOST_WIDE_INT ll_bitsize, ll_bitpos, lr_bitsize, lr_bitpos;
  HOST_WIDE_INT rl_bitsize, rl_bitpos, rr_bitsize, rr_bitpos;
  HOST_WIDE_INT xll_bitpos, xlr_bitpos, xrl_bitpos, xrr_bitpos;
  HOST_WIDE_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 lntype, rntype, 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);

  /* Simplify (x<y) && (x==y) into (x<=y) and related optimizations.  */
  if (simple_operand_p (ll_arg)
      && simple_operand_p (lr_arg)
      && !FLOAT_TYPE_P (TREE_TYPE (ll_arg)))
    {
      int compcode;

      if (operand_equal_p (ll_arg, rl_arg, 0)
          && operand_equal_p (lr_arg, rr_arg, 0))
        {
          int lcompcode, rcompcode;

          lcompcode = comparison_to_compcode (lcode);
          rcompcode = comparison_to_compcode (rcode);
          compcode = (code == TRUTH_AND_EXPR)
                     ? lcompcode & rcompcode
                     : lcompcode | rcompcode;