decl.c (gnat_to_gnu_entity): Create IMPORTED_DECL nodes to describe the subprogram...

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

/* Constant folding for calls to built-in and internal functions.
   Copyright (C) 1988-2015 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 3, 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 COPYING3.  If not see
<http://www.gnu.org/licenses/>.  */

#include "config.h"
#include "system.h"
#include "coretypes.h"
#include "realmpfr.h"
#include "tree.h"
#include "stor-layout.h"
#include "options.h"
#include "fold-const.h"
#include "fold-const-call.h"
#include "tm.h" /* For C[LT]Z_DEFINED_AT_ZERO.  */

/* Functions that test for certain constant types, abstracting away the
   decision about whether to check for overflow.  */

static inline bool
integer_cst_p (tree t)
{
  return TREE_CODE (t) == INTEGER_CST && !TREE_OVERFLOW (t);
}

static inline bool
real_cst_p (tree t)
{
  return TREE_CODE (t) == REAL_CST && !TREE_OVERFLOW (t);
}

static inline bool
complex_cst_p (tree t)
{
  return TREE_CODE (t) == COMPLEX_CST;
}

/* Return true if ARG is a constant in the range of the host size_t.
   Store it in *SIZE_OUT if so.  */

static inline bool
host_size_t_cst_p (tree t, size_t *size_out)
{
  if (integer_cst_p (t)
      && wi::min_precision (t, UNSIGNED) <= sizeof (size_t) * CHAR_BIT)
    {
      *size_out = tree_to_uhwi (t);
      return true;
    }
  return false;
}

/* RES is the result of a comparison in which < 0 means "less", 0 means
   "equal" and > 0 means "more".  Canonicalize it to -1, 0 or 1 and
   return it in type TYPE.  */

static inline tree
build_cmp_result (tree type, int res)
{
  return build_int_cst (type, res < 0 ? -1 : res > 0 ? 1 : 0);
}

/* M is the result of trying to constant-fold an expression (starting
   with clear MPFR flags) and INEXACT says whether the result in M is
   exact or inexact.  Return true if M can be used as a constant-folded
   result in format FORMAT, storing the value in *RESULT if so.  */

static bool
do_mpfr_ckconv (real_value *result, mpfr_srcptr m, bool inexact,
                const real_format *format)
{
  /* Proceed iff we get a normal number, i.e. not NaN or Inf and no
     overflow/underflow occurred.  If -frounding-math, proceed iff the
     result of calling FUNC was exact.  */
  if (!mpfr_number_p (m)
      || mpfr_overflow_p ()
      || mpfr_underflow_p ()
      || (flag_rounding_math && inexact))
    return false;

  REAL_VALUE_TYPE tmp;
  real_from_mpfr (&tmp, m, format, GMP_RNDN);

  /* Proceed iff GCC's REAL_VALUE_TYPE can hold the MPFR values.
     If the REAL_VALUE_TYPE is zero but the mpft_t is not, then we
     underflowed in the conversion.  */
  if (!real_isfinite (&tmp)
      || ((tmp.cl == rvc_zero) != (mpfr_zero_p (m) != 0)))
    return false;

  real_convert (result, format, &tmp);
  return real_identical (result, &tmp);
}

/* Try to evaluate:

      *RESULT = f (*ARG)

   in format FORMAT, given that FUNC is the MPFR implementation of f.
   Return true on success.  */

static bool
do_mpfr_arg1 (real_value *result,
              int (*func) (mpfr_ptr, mpfr_srcptr, mpfr_rnd_t),
              const real_value *arg, const real_format *format)
{
  /* To proceed, MPFR must exactly represent the target floating point
     format, which only happens when the target base equals two.  */
  if (format->b != 2 || !real_isfinite (arg))
    return false;

  int prec = format->p;
  mp_rnd_t rnd = format->round_towards_zero ? GMP_RNDZ : GMP_RNDN;
  mpfr_t m;

  mpfr_init2 (m, prec);
  mpfr_from_real (m, arg, GMP_RNDN);
  mpfr_clear_flags ();
  bool inexact = func (m, m, rnd);
  bool ok = do_mpfr_ckconv (result, m, inexact, format);
  mpfr_clear (m);

  return ok;
}

/* Try to evaluate:

      *RESULT_SIN = sin (*ARG);
      *RESULT_COS = cos (*ARG);

   for format FORMAT.  Return true on success.  */

static bool
do_mpfr_sincos (real_value *result_sin, real_value *result_cos,
                const real_value *arg, const real_format *format)
{
  /* To proceed, MPFR must exactly represent the target floating point
     format, which only happens when the target base equals two.  */
  if (format->b != 2 || !real_isfinite (arg))
    return false;

  int prec = format->p;
  mp_rnd_t rnd = format->round_towards_zero ? GMP_RNDZ : GMP_RNDN;
  mpfr_t m, ms, mc;

  mpfr_inits2 (prec, m, ms, mc, NULL);
  mpfr_from_real (m, arg, GMP_RNDN);
  mpfr_clear_flags ();
  bool inexact = mpfr_sin_cos (ms, mc, m, rnd);
  bool ok = (do_mpfr_ckconv (result_sin, ms, inexact, format)
             && do_mpfr_ckconv (result_cos, mc, inexact, format));
  mpfr_clears (m, ms, mc, NULL);

  return ok;
}

/* Try to evaluate:

      *RESULT = f (*ARG0, *ARG1)

   in format FORMAT, given that FUNC is the MPFR implementation of f.
   Return true on success.  */

static bool
do_mpfr_arg2 (real_value *result,
              int (*func) (mpfr_ptr, mpfr_srcptr, mpfr_srcptr, mpfr_rnd_t),
              const real_value *arg0, const real_value *arg1,
              const real_format *format)
{
  /* To proceed, MPFR must exactly represent the target floating point
     format, which only happens when the target base equals two.  */
  if (format->b != 2 || !real_isfinite (arg0) || !real_isfinite (arg1))
    return false;

  int prec = format->p;
  mp_rnd_t rnd = format->round_towards_zero ? GMP_RNDZ : GMP_RNDN;
  mpfr_t m0, m1;

  mpfr_inits2 (prec, m0, m1, NULL);
  mpfr_from_real (m0, arg0, GMP_RNDN);
  mpfr_from_real (m1, arg1, GMP_RNDN);
  mpfr_clear_flags ();
  bool inexact = func (m0, m0, m1, rnd);
  bool ok = do_mpfr_ckconv (result, m0, inexact, format);
  mpfr_clears (m0, m1, NULL);

  return ok;
}

/* Try to evaluate:

      *RESULT = f (ARG0, *ARG1)

   in format FORMAT, given that FUNC is the MPFR implementation of f.
   Return true on success.  */

static bool
do_mpfr_arg2 (real_value *result,
              int (*func) (mpfr_ptr, long, mpfr_srcptr, mp_rnd_t),
              const wide_int_ref &arg0, const real_value *arg1,
              const real_format *format)
{
  if (format->b != 2 || !real_isfinite (arg1))
    return false;

  int prec = format->p;
  mp_rnd_t rnd = format->round_towards_zero ? GMP_RNDZ : GMP_RNDN;
  mpfr_t m;

  mpfr_init2 (m, prec);
  mpfr_from_real (m, arg1, GMP_RNDN);
  mpfr_clear_flags ();
  bool inexact = func (m, arg0.to_shwi (), m, rnd);
  bool ok = do_mpfr_ckconv (result, m, inexact, format);
  mpfr_clear (m);

  return ok;
}

/* Try to evaluate:

      *RESULT = f (*ARG0, *ARG1, *ARG2)

   in format FORMAT, given that FUNC is the MPFR implementation of f.
   Return true on success.  */

static bool
do_mpfr_arg3 (real_value *result,
              int (*func) (mpfr_ptr, mpfr_srcptr, mpfr_srcptr,
                           mpfr_srcptr, mpfr_rnd_t),
              const real_value *arg0, const real_value *arg1,
              const real_value *arg2, const real_format *format)
{
  /* To proceed, MPFR must exactly represent the target floating point
     format, which only happens when the target base equals two.  */
  if (format->b != 2
      || !real_isfinite (arg0)
      || !real_isfinite (arg1)
      || !real_isfinite (arg2))
    return false;

  int prec = format->p;
  mp_rnd_t rnd = format->round_towards_zero ? GMP_RNDZ : GMP_RNDN;
  mpfr_t m0, m1, m2;

  mpfr_inits2 (prec, m0, m1, m2, NULL);
  mpfr_from_real (m0, arg0, GMP_RNDN);
  mpfr_from_real (m1, arg1, GMP_RNDN);
  mpfr_from_real (m2, arg2, GMP_RNDN);
  mpfr_clear_flags ();
  bool inexact = func (m0, m0, m1, m2, rnd);
  bool ok = do_mpfr_ckconv (result, m0, inexact, format);
  mpfr_clears (m0, m1, m2, NULL);

  return ok;
}

/* M is the result of trying to constant-fold an expression (starting
   with clear MPFR flags) and INEXACT says whether the result in M is
   exact or inexact.  Return true if M can be used as a constant-folded
   result in which the real and imaginary parts have format FORMAT.
   Store those parts in *RESULT_REAL and *RESULT_IMAG if so.  */

static bool
do_mpc_ckconv (real_value *result_real, real_value *result_imag,
               mpc_srcptr m, bool inexact, const real_format *format)
{
  /* Proceed iff we get a normal number, i.e. not NaN or Inf and no
     overflow/underflow occurred.  If -frounding-math, proceed iff the
     result of calling FUNC was exact.  */
  if (!mpfr_number_p (mpc_realref (m))
      || !mpfr_number_p (mpc_imagref (m))
      || mpfr_overflow_p ()
      || mpfr_underflow_p ()
      || (flag_rounding_math && inexact))
    return false;

  REAL_VALUE_TYPE tmp_real, tmp_imag;
  real_from_mpfr (&tmp_real, mpc_realref (m), format, GMP_RNDN);
  real_from_mpfr (&tmp_imag, mpc_imagref (m), format, GMP_RNDN);

  /* Proceed iff GCC's REAL_VALUE_TYPE can hold the MPFR values.
     If the REAL_VALUE_TYPE is zero but the mpft_t is not, then we
     underflowed in the conversion.  */
  if (!real_isfinite (&tmp_real)
      || !real_isfinite (&tmp_imag)
      || (tmp_real.cl == rvc_zero) != (mpfr_zero_p (mpc_realref (m)) != 0)
      || (tmp_imag.cl == rvc_zero) != (mpfr_zero_p (mpc_imagref (m)) != 0))
    return false;

  real_convert (result_real, format, &tmp_real);
  real_convert (result_imag, format, &tmp_imag);

  return (real_identical (result_real, &tmp_real)
          && real_identical (result_imag, &tmp_imag));
}

/* Try to evaluate:

      RESULT = f (ARG)

   in format FORMAT, given that FUNC is the mpc implementation of f.
   Return true on success.  Both RESULT and ARG are represented as
   real and imaginary pairs.  */

static bool
do_mpc_arg1 (real_value *result_real, real_value *result_imag,
             int (*func) (mpc_ptr, mpc_srcptr, mpc_rnd_t),
             const real_value *arg_real, const real_value *arg_imag,
             const real_format *format)
{
  /* To proceed, MPFR must exactly represent the target floating point
     format, which only happens when the target base equals two.  */
  if (format->b != 2
      || !real_isfinite (arg_real)
      || !real_isfinite (arg_imag))
    return false;

  int prec = format->p;
  mpc_rnd_t crnd = format->round_towards_zero ? MPC_RNDZZ : MPC_RNDNN;
  mpc_t m;

  mpc_init2 (m, prec);
  mpfr_from_real (mpc_realref (m), arg_real, GMP_RNDN);
  mpfr_from_real (mpc_imagref (m), arg_imag, GMP_RNDN);
  mpfr_clear_flags ();
  bool inexact = func (m, m, crnd);
  bool ok = do_mpc_ckconv (result_real, result_imag, m, inexact, format);
  mpc_clear (m);

  return ok;
}

/* Try to evaluate:

      RESULT = f (ARG0, ARG1)

   in format FORMAT, given that FUNC is the mpc implementation of f.
   Return true on success.  RESULT, ARG0 and ARG1 are represented as
   real and imaginary pairs.  */

static bool
do_mpc_arg2 (real_value *result_real, real_value *result_imag,
             int (*func)(mpc_ptr, mpc_srcptr, mpc_srcptr, mpc_rnd_t),
             const real_value *arg0_real, const real_value *arg0_imag,
             const real_value *arg1_real, const real_value *arg1_imag,
             const real_format *format)
{
  if (!real_isfinite (arg0_real)
      || !real_isfinite (arg0_imag)
      || !real_isfinite (arg1_real)
      || !real_isfinite (arg1_imag))
    return false;

  int prec = format->p;
  mpc_rnd_t crnd = format->round_towards_zero ? MPC_RNDZZ : MPC_RNDNN;
  mpc_t m0, m1;

  mpc_init2 (m0, prec);
  mpc_init2 (m1, prec);
  mpfr_from_real (mpc_realref (m0), arg0_real, GMP_RNDN);
  mpfr_from_real (mpc_imagref (m0), arg0_imag, GMP_RNDN);
  mpfr_from_real (mpc_realref (m1), arg1_real, GMP_RNDN);
  mpfr_from_real (mpc_imagref (m1), arg1_imag, GMP_RNDN);
  mpfr_clear_flags ();
  bool inexact = func (m0, m0, m1, crnd);
  bool ok = do_mpc_ckconv (result_real, result_imag, m0, inexact, format);
  mpc_clear (m0);
  mpc_clear (m1);

  return ok;
}

/* Try to evaluate:

      *RESULT = logb (*ARG)

   in format FORMAT.  Return true on success.  */

static bool
fold_const_logb (real_value *result, const real_value *arg,
                 const real_format *format)
{
  switch (arg->cl)
    {
    case rvc_nan:
      /* If arg is +-NaN, then return it.  */
      *result = *arg;
      return true;

    case rvc_inf:
      /* If arg is +-Inf, then return +Inf.  */
      *result = *arg;
      result->sign = 0;
      return true;

    case rvc_zero:
      /* Zero may set errno and/or raise an exception.  */
      return false;

    case rvc_normal:
      /* For normal numbers, proceed iff radix == 2.  In GCC,
         normalized significands are in the range [0.5, 1.0).  We
         want the exponent as if they were [1.0, 2.0) so get the
         exponent and subtract 1.  */
      if (format->b == 2)
        {
          real_from_integer (result, format, REAL_EXP (arg) - 1, SIGNED);
          return true;
        }
      return false;
    }
  gcc_unreachable ();
}

/* Try to evaluate:

      *RESULT = significand (*ARG)

   in format FORMAT.  Return true on success.  */

static bool
fold_const_significand (real_value *result, const real_value *arg,
                        const real_format *format)
{
  switch (arg->cl)
    {
    case rvc_zero:
    case rvc_nan:
    case rvc_inf:
      /* If arg is +-0, +-Inf or +-NaN, then return it.  */
      *result = *arg;
      return true;

    case rvc_normal:
      /* For normal numbers, proceed iff radix == 2.  */
      if (format->b == 2)
        {
          *result = *arg;
          /* In GCC, normalized significands are in the range [0.5, 1.0).
             We want them to be [1.0, 2.0) so set the exponent to 1.  */
          SET_REAL_EXP (result, 1);
          return true;
        }
      return false;
    }
  gcc_unreachable ();
}

/* Try to evaluate:

      *RESULT = f (*ARG)

   where FORMAT is the format of *ARG and PRECISION is the number of
   significant bits in the result.  Return true on success.  */

static bool
fold_const_conversion (wide_int *result,
                       void (*fn) (real_value *, format_helper,
                                   const real_value *),
                       const real_value *arg, unsigned int precision,
                       const real_format *format)
{
  if (!real_isfinite (arg))
    return false;

  real_value rounded;
  fn (&rounded, format, arg);

  bool fail = false;
  *result = real_to_integer (&rounded, &fail, precision);
  return !fail;
}

/* Try to evaluate:

      *RESULT = pow (*ARG0, *ARG1)

   in format FORMAT.  Return true on success.  */

static bool
fold_const_pow (real_value *result, const real_value *arg0,
                const real_value *arg1, const real_format *format)
{
  if (do_mpfr_arg2 (result, mpfr_pow, arg0, arg1, format))
    return true;

  /* Check for an integer exponent.  */
  REAL_VALUE_TYPE cint1;
  HOST_WIDE_INT n1 = real_to_integer (arg1);
  real_from_integer (&cint1, VOIDmode, n1, SIGNED);
  /* Attempt to evaluate pow at compile-time, unless this should
     raise an exception.  */
  if (real_identical (arg1, &cint1)
      && (n1 > 0
          || (!flag_trapping_math && !flag_errno_math)
          || !real_equal (arg0, &dconst0)))
    {
      bool inexact = real_powi (result, format, arg0, n1);
      if (flag_unsafe_math_optimizations || !inexact)
        return true;
    }

  return false;
}

/* Try to evaluate:

      *RESULT = ldexp (*ARG0, ARG1)

   in format FORMAT.  Return true on success.  */

static bool
fold_const_builtin_load_exponent (real_value *result, const real_value *arg0,
                                  const wide_int_ref &arg1,
                                  const real_format *format)
{
  /* Bound the maximum adjustment to twice the range of the
     mode's valid exponents.  Use abs to ensure the range is
     positive as a sanity check.  */
  int max_exp_adj = 2 * labs (format->emax - format->emin);

  /* The requested adjustment must be inside this range.  This
     is a preliminary cap to avoid things like overflow, we
     may still fail to compute the result for other reasons.  */
  if (wi::les_p (arg1, -max_exp_adj) || wi::ges_p (arg1, max_exp_adj))
    return false;

  REAL_VALUE_TYPE initial_result;
  real_ldexp (&initial_result, arg0, arg1.to_shwi ());

  /* Ensure we didn't overflow.  */
  if (real_isinf (&initial_result))
    return false;

  /* Only proceed if the target mode can hold the
     resulting value.  */
  *result = real_value_truncate (format, initial_result);
  return real_equal (&initial_result, result);
}

/* Fold a call to __builtin_nan or __builtin_nans with argument ARG and
   return type TYPE.  QUIET is true if a quiet rather than signalling
   NaN is required.  */

static tree
fold_const_builtin_nan (tree type, tree arg, bool quiet)
{
  REAL_VALUE_TYPE real;
  const char *str = c_getstr (arg);
  if (str && real_nan (&real, str, quiet, TYPE_MODE (type)))
    return build_real (type, real);
  return NULL_TREE;
}

/* Try to evaluate:

      *RESULT = FN (*ARG)

   in format FORMAT.  Return true on success.  */

static bool
fold_const_call_ss (real_value *result, built_in_function fn,
                    const real_value *arg, const real_format *format)
{
  switch (fn)
    {
    CASE_FLT_FN (BUILT_IN_SQRT):
      return (real_compare (GE_EXPR, arg, &dconst0)
              && do_mpfr_arg1 (result, mpfr_sqrt, arg, format));

    CASE_FLT_FN (BUILT_IN_CBRT):
      return do_mpfr_arg1 (result, mpfr_cbrt, arg, format);

    CASE_FLT_FN (BUILT_IN_ASIN):
      return (real_compare (GE_EXPR, arg, &dconstm1)
              && real_compare (LE_EXPR, arg, &dconst1)
              && do_mpfr_arg1 (result, mpfr_asin, arg, format));

    CASE_FLT_FN (BUILT_IN_ACOS):
      return (real_compare (GE_EXPR, arg, &dconstm1)
              && real_compare (LE_EXPR, arg, &dconst1)
              && do_mpfr_arg1 (result, mpfr_acos, arg, format));

    CASE_FLT_FN (BUILT_IN_ATAN):
      return do_mpfr_arg1 (result, mpfr_atan, arg, format);

    CASE_FLT_FN (BUILT_IN_ASINH):
      return do_mpfr_arg1 (result, mpfr_asinh, arg, format);

    CASE_FLT_FN (BUILT_IN_ACOSH):
      return (real_compare (GE_EXPR, arg, &dconst1)
              && do_mpfr_arg1 (result, mpfr_acosh, arg, format));

    CASE_FLT_FN (BUILT_IN_ATANH):
      return (real_compare (GE_EXPR, arg, &dconstm1)
              && real_compare (LE_EXPR, arg, &dconst1)
              && do_mpfr_arg1 (result, mpfr_atanh, arg, format));

    CASE_FLT_FN (BUILT_IN_SIN):
      return do_mpfr_arg1 (result, mpfr_sin, arg, format);

    CASE_FLT_FN (BUILT_IN_COS):
      return do_mpfr_arg1 (result, mpfr_cos, arg, format);

    CASE_FLT_FN (BUILT_IN_TAN):
      return do_mpfr_arg1 (result, mpfr_tan, arg, format);

    CASE_FLT_FN (BUILT_IN_SINH):
      return do_mpfr_arg1 (result, mpfr_sinh, arg, format);

    CASE_FLT_FN (BUILT_IN_COSH):
      return do_mpfr_arg1 (result, mpfr_cosh, arg, format);

    CASE_FLT_FN (BUILT_IN_TANH):
      return do_mpfr_arg1 (result, mpfr_tanh, arg, format);

    CASE_FLT_FN (BUILT_IN_ERF):
      return do_mpfr_arg1 (result, mpfr_erf, arg, format);

    CASE_FLT_FN (BUILT_IN_ERFC):
      return do_mpfr_arg1 (result, mpfr_erfc, arg, format);

    CASE_FLT_FN (BUILT_IN_TGAMMA):
      return do_mpfr_arg1 (result, mpfr_gamma, arg, format);

    CASE_FLT_FN (BUILT_IN_EXP):
      return do_mpfr_arg1 (result, mpfr_exp, arg, format);

    CASE_FLT_FN (BUILT_IN_EXP2):
      return do_mpfr_arg1 (result, mpfr_exp2, arg, format);

    CASE_FLT_FN (BUILT_IN_EXP10):
    CASE_FLT_FN (BUILT_IN_POW10):
      return do_mpfr_arg1 (result, mpfr_exp10, arg, format);

    CASE_FLT_FN (BUILT_IN_EXPM1):
      return do_mpfr_arg1 (result, mpfr_expm1, arg, format);

    CASE_FLT_FN (BUILT_IN_LOG):
      return (real_compare (GT_EXPR, arg, &dconst0)
              && do_mpfr_arg1 (result, mpfr_log, arg, format));

    CASE_FLT_FN (BUILT_IN_LOG2):
      return (real_compare (GT_EXPR, arg, &dconst0)
              && do_mpfr_arg1 (result, mpfr_log2, arg, format));

    CASE_FLT_FN (BUILT_IN_LOG10):
      return (real_compare (GT_EXPR, arg, &dconst0)
              && do_mpfr_arg1 (result, mpfr_log10, arg, format));

    CASE_FLT_FN (BUILT_IN_LOG1P):
      return (real_compare (GT_EXPR, arg, &dconstm1)
              && do_mpfr_arg1 (result, mpfr_log1p, arg, format));

    CASE_FLT_FN (BUILT_IN_J0):
      return do_mpfr_arg1 (result, mpfr_j0, arg, format);

    CASE_FLT_FN (BUILT_IN_J1):
      return do_mpfr_arg1 (result, mpfr_j1, arg, format);

    CASE_FLT_FN (BUILT_IN_Y0):
      return (real_compare (GT_EXPR, arg, &dconst0)
              && do_mpfr_arg1 (result, mpfr_y0, arg, format));

    CASE_FLT_FN (BUILT_IN_Y1):
      return (real_compare (GT_EXPR, arg, &dconst0)
              && do_mpfr_arg1 (result, mpfr_y1, arg, format));

    CASE_FLT_FN (BUILT_IN_FLOOR):
      if (!REAL_VALUE_ISNAN (*arg) || !flag_errno_math)
        {
          real_floor (result, format, arg);
          return true;
        }
      return false;

    CASE_FLT_FN (BUILT_IN_CEIL):
      if (!REAL_VALUE_ISNAN (*arg) || !flag_errno_math)
        {
          real_ceil (result, format, arg);
          return true;
        }
      return false;

    CASE_FLT_FN (BUILT_IN_TRUNC):
      real_trunc (result, format, arg);
      return true;

    CASE_FLT_FN (BUILT_IN_ROUND):
      if (!REAL_VALUE_ISNAN (*arg) || !flag_errno_math)
        {
          real_round (result, format, arg);
          return true;
        }
      return false;

    CASE_FLT_FN (BUILT_IN_LOGB):
      return fold_const_logb (result, arg, format);

    CASE_FLT_FN (BUILT_IN_SIGNIFICAND):
      return fold_const_significand (result, arg, format);

    default:
      return false;
    }
}

/* Try to evaluate:

      *RESULT = FN (*ARG)

   where FORMAT is the format of ARG and PRECISION is the number of
   significant bits in the result.  Return true on success.  */

static bool
fold_const_call_ss (wide_int *result, built_in_function fn,
                    const real_value *arg, unsigned int precision,
                    const real_format *format)
{
  switch (fn)
    {
    CASE_FLT_FN (BUILT_IN_SIGNBIT):
      if (real_isneg (arg))
        *result = wi::one (precision);
      else
        *result = wi::zero (precision);
      return true;

    CASE_FLT_FN (BUILT_IN_ILOGB):
      /* For ilogb we don't know FP_ILOGB0, so only handle normal values.
         Proceed iff radix == 2.  In GCC, normalized significands are in
         the range [0.5, 1.0).  We want the exponent as if they were
         [1.0, 2.0) so get the exponent and subtract 1.  */
      if (arg->cl == rvc_normal && format->b == 2)
        {
          *result = wi::shwi (REAL_EXP (arg) - 1, precision);
          return true;
        }
      return false;

    CASE_FLT_FN (BUILT_IN_ICEIL):
    CASE_FLT_FN (BUILT_IN_LCEIL):
    CASE_FLT_FN (BUILT_IN_LLCEIL):
      return fold_const_conversion (result, real_ceil, arg,
                                    precision, format);

    CASE_FLT_FN (BUILT_IN_LFLOOR):
    CASE_FLT_FN (BUILT_IN_IFLOOR):
    CASE_FLT_FN (BUILT_IN_LLFLOOR):
      return fold_const_conversion (result, real_floor, arg,
                                    precision, format);

    CASE_FLT_FN (BUILT_IN_IROUND):
    CASE_FLT_FN (BUILT_IN_LROUND):
    CASE_FLT_FN (BUILT_IN_LLROUND):
      return fold_const_conversion (result, real_round, arg,
                                    precision, format);

    CASE_FLT_FN (BUILT_IN_IRINT):
    CASE_FLT_FN (BUILT_IN_LRINT):
    CASE_FLT_FN (BUILT_IN_LLRINT):
      /* Not yet folded to a constant.  */
      return false;

    CASE_FLT_FN (BUILT_IN_FINITE):
    case BUILT_IN_FINITED32:
    case BUILT_IN_FINITED64:
    case BUILT_IN_FINITED128:
    case BUILT_IN_ISFINITE:
      *result = wi::shwi (real_isfinite (arg) ? 1 : 0, precision);
      return true;

    CASE_FLT_FN (BUILT_IN_ISINF):
    case BUILT_IN_ISINFD32:
    case BUILT_IN_ISINFD64:
    case BUILT_IN_ISINFD128:
      if (real_isinf (arg))
        *result = wi::shwi (arg->sign ? -1 : 1, precision);
      else
        *result = wi::shwi (0, precision);
      return true;

    CASE_FLT_FN (BUILT_IN_ISNAN):
    case BUILT_IN_ISNAND32:
    case BUILT_IN_ISNAND64:
    case BUILT_IN_ISNAND128:
      *result = wi::shwi (real_isnan (arg) ? 1 : 0, precision);
      return true;

    default:
      return false;
    }
}

/* Try to evaluate:

      *RESULT = FN (ARG)

   where ARG_TYPE is the type of ARG and PRECISION is the number of bits
   in the result.  Return true on success.  */

static bool
fold_const_call_ss (wide_int *result, built_in_function fn,
                    const wide_int_ref &arg, unsigned int precision,
                    tree arg_type)
{
  switch (fn)
    {
    CASE_INT_FN (BUILT_IN_FFS):
      *result = wi::shwi (wi::ffs (arg), precision);
      return true;

    CASE_INT_FN (BUILT_IN_CLZ):
      {
        int tmp;
        if (wi::ne_p (arg, 0))
          tmp = wi::clz (arg);
        else if (! CLZ_DEFINED_VALUE_AT_ZERO (TYPE_MODE (arg_type), tmp))
          tmp = TYPE_PRECISION (arg_type);
        *result = wi::shwi (tmp, precision);
        return true;
      }

    CASE_INT_FN (BUILT_IN_CTZ):
      {
        int tmp;
        if (wi::ne_p (arg, 0))
          tmp = wi::ctz (arg);
        else if (! CTZ_DEFINED_VALUE_AT_ZERO (TYPE_MODE (arg_type), tmp))
          tmp = TYPE_PRECISION (arg_type);
        *result = wi::shwi (tmp, precision);
        return true;
      }

    CASE_INT_FN (BUILT_IN_CLRSB):
      *result = wi::shwi (wi::clrsb (arg), precision);
      return true;

    CASE_INT_FN (BUILT_IN_POPCOUNT):
      *result = wi::shwi (wi::popcount (arg), precision);
      return true;

    CASE_INT_FN (BUILT_IN_PARITY):
      *result = wi::shwi (wi::parity (arg), precision);
      return true;

    case BUILT_IN_BSWAP16:
    case BUILT_IN_BSWAP32:
    case BUILT_IN_BSWAP64:
      *result = wide_int::from (arg, precision, TYPE_SIGN (arg_type)).bswap ();
      return true;

    default:
      return false;
    }
}

/* Try to evaluate:

      RESULT = FN (*ARG)

   where FORMAT is the format of ARG and of the real and imaginary parts
   of RESULT, passed as RESULT_REAL and RESULT_IMAG respectively.  Return
   true on success.  */

static bool
fold_const_call_cs (real_value *result_real, real_value *result_imag,
                    built_in_function fn, const real_value *arg,
                    const real_format *format)
{
  switch (fn)
    {
    CASE_FLT_FN (BUILT_IN_CEXPI):
      /* cexpi(x+yi) = cos(x)+sin(y)*i.  */
      return do_mpfr_sincos (result_imag, result_real, arg, format);

    default:
      return false;
    }
}

/* Try to evaluate:

      *RESULT = fn (ARG)

   where FORMAT is the format of RESULT and of the real and imaginary parts
   of ARG, passed as ARG_REAL and ARG_IMAG respectively.  Return true on
   success.  */

static bool
fold_const_call_sc (real_value *result, built_in_function fn,
                    const real_value *arg_real, const real_value *arg_imag,
                    const real_format *format)
{
  switch (fn)
    {
    CASE_FLT_FN (BUILT_IN_CABS):
      return do_mpfr_arg2 (result, mpfr_hypot, arg_real, arg_imag, format);

    default:
      return false;
    }
}

/* Try to evaluate:

      RESULT = fn (ARG)

   where FORMAT is the format of the real and imaginary parts of RESULT
   (RESULT_REAL and RESULT_IMAG) and of ARG (ARG_REAL and ARG_IMAG).
   Return true on success.  */

static bool
fold_const_call_cc (real_value *result_real, real_value *result_imag,
                    built_in_function fn, const real_value *arg_real,
                    const real_value *arg_imag, const real_format *format)
{
  switch (fn)
    {
    CASE_FLT_FN (BUILT_IN_CCOS):
      return do_mpc_arg1 (result_real, result_imag, mpc_cos,
                          arg_real, arg_imag, format);

    CASE_FLT_FN (BUILT_IN_CCOSH):
      return do_mpc_arg1 (result_real, result_imag, mpc_cosh,
                          arg_real, arg_imag, format);

    CASE_FLT_FN (BUILT_IN_CPROJ):
      if (real_isinf (arg_real) || real_isinf (arg_imag))
        {
          real_inf (result_real);
          *result_imag = dconst0;
          result_imag->sign = arg_imag->sign;
        }
      else
        {
          *result_real = *arg_real;
          *result_imag = *arg_imag;
        }
      return true;

    CASE_FLT_FN (BUILT_IN_CSIN):
      return do_mpc_arg1 (result_real, result_imag, mpc_sin,
                          arg_real, arg_imag, format);

    CASE_FLT_FN (BUILT_IN_CSINH):
      return do_mpc_arg1 (result_real, result_imag, mpc_sinh,
                          arg_real, arg_imag, format);

    CASE_FLT_FN (BUILT_IN_CTAN):
      return do_mpc_arg1 (result_real, result_imag, mpc_tan,
                          arg_real, arg_imag, format);

    CASE_FLT_FN (BUILT_IN_CTANH):
      return do_mpc_arg1 (result_real, result_imag, mpc_tanh,
                          arg_real, arg_imag, format);

    CASE_FLT_FN (BUILT_IN_CLOG):
      return do_mpc_arg1 (result_real, result_imag, mpc_log,
                          arg_real, arg_imag, format);

    CASE_FLT_FN (BUILT_IN_CSQRT):
      return do_mpc_arg1 (result_real, result_imag, mpc_sqrt,
                          arg_real, arg_imag, format);

    CASE_FLT_FN (BUILT_IN_CASIN):
      return do_mpc_arg1 (result_real, result_imag, mpc_asin,
                          arg_real, arg_imag, format);

    CASE_FLT_FN (BUILT_IN_CACOS):
      return do_mpc_arg1 (result_real, result_imag, mpc_acos,
                          arg_real, arg_imag, format);

    CASE_FLT_FN (BUILT_IN_CATAN):
      return do_mpc_arg1 (result_real, result_imag, mpc_atan,
                          arg_real, arg_imag, format);

    CASE_FLT_FN (BUILT_IN_CASINH):
      return do_mpc_arg1 (result_real, result_imag, mpc_asinh,
                          arg_real, arg_imag, format);

    CASE_FLT_FN (BUILT_IN_CACOSH):
      return do_mpc_arg1 (result_real, result_imag, mpc_acosh,
                          arg_real, arg_imag, format);

    CASE_FLT_FN (BUILT_IN_CATANH):
      return do_mpc_arg1 (result_real, result_imag, mpc_atanh,
                          arg_real, arg_imag, format);

    CASE_FLT_FN (BUILT_IN_CEXP):
      return do_mpc_arg1 (result_real, result_imag, mpc_exp,
                          arg_real, arg_imag, format);

    default:
      return false;
    }
}

/* Subroutine of fold_const_call, with the same interface.  Handle cases
   where the arguments and result are numerical.  */

static tree
fold_const_call_1 (built_in_function fn, tree type, tree arg)
{
  machine_mode mode = TYPE_MODE (type);
  machine_mode arg_mode = TYPE_MODE (TREE_TYPE (arg));

  if (integer_cst_p (arg))
    {
      if (SCALAR_INT_MODE_P (mode))
        {
          wide_int result;
          if (fold_const_call_ss (&result, fn, arg, TYPE_PRECISION (type),
                                  TREE_TYPE (arg)))
            return wide_int_to_tree (type, result);
        }
      return NULL_TREE;
    }

  if (real_cst_p (arg))
    {
      gcc_checking_assert (SCALAR_FLOAT_MODE_P (arg_mode));
      if (mode == arg_mode)
        {
          /* real -> real.  */
          REAL_VALUE_TYPE result;
          if (fold_const_call_ss (&result, fn, TREE_REAL_CST_PTR (arg),
                                  REAL_MODE_FORMAT (mode)))
            return build_real (type, result);
        }
      else if (COMPLEX_MODE_P (mode)
               && GET_MODE_INNER (mode) == arg_mode)
        {
          /* real -> complex real.  */
          REAL_VALUE_TYPE result_real, result_imag;
          if (fold_const_call_cs (&result_real, &result_imag, fn,
                                  TREE_REAL_CST_PTR (arg),
                                  REAL_MODE_FORMAT (arg_mode)))
            return build_complex (type,
                                  build_real (TREE_TYPE (type), result_real),
                                  build_real (TREE_TYPE (type), result_imag));
        }
      else if (INTEGRAL_TYPE_P (type))
        {
          /* real -> int.  */
          wide_int result;
          if (fold_const_call_ss (&result, fn,
                                  TREE_REAL_CST_PTR (arg),
                                  TYPE_PRECISION (type),
                                  REAL_MODE_FORMAT (arg_mode)))
            return wide_int_to_tree (type, result);
        }
      return NULL_TREE;
    }

  if (complex_cst_p (arg))
    {
      gcc_checking_assert (COMPLEX_MODE_P (arg_mode));
      machine_mode inner_mode = GET_MODE_INNER (arg_mode);
      tree argr = TREE_REALPART (arg);
      tree argi = TREE_IMAGPART (arg);
      if (mode == arg_mode
          && real_cst_p (argr)
          && real_cst_p (argi))
        {
          /* complex real -> complex real.  */
          REAL_VALUE_TYPE result_real, result_imag;
          if (fold_const_call_cc (&result_real, &result_imag, fn,
                                  TREE_REAL_CST_PTR (argr),
                                  TREE_REAL_CST_PTR (argi),
                                  REAL_MODE_FORMAT (inner_mode)))
            return build_complex (type,
                                  build_real (TREE_TYPE (type), result_real),
                                  build_real (TREE_TYPE (type), result_imag));
        }
      if (mode == inner_mode
          && real_cst_p (argr)
          && real_cst_p (argi))
        {
          /* complex real -> real.  */
          REAL_VALUE_TYPE result;
          if (fold_const_call_sc (&result, fn,
                                  TREE_REAL_CST_PTR (argr),
                                  TREE_REAL_CST_PTR (argi),
                                  REAL_MODE_FORMAT (inner_mode)))
            return build_real (type, result);
        }
      return NULL_TREE;
    }

  return NULL_TREE;
}

/* Try to fold FN (ARG) to a constant.  Return the constant on success,
   otherwise return null.  TYPE is the type of the return value.  */

tree
fold_const_call (built_in_function fn, tree type, tree arg)
{
  switch (fn)
    {
    case BUILT_IN_STRLEN:
      if (const char *str = c_getstr (arg))
        return build_int_cst (type, strlen (str));
      return NULL_TREE;

    CASE_FLT_FN (BUILT_IN_NAN):
    case BUILT_IN_NAND32:
    case BUILT_IN_NAND64:
    case BUILT_IN_NAND128:
      return fold_const_builtin_nan (type, arg, true);

    CASE_FLT_FN (BUILT_IN_NANS):
      return fold_const_builtin_nan (type, arg, false);

    default:
      return fold_const_call_1 (fn, type, arg);
    }
}

/* Try to evaluate:

      *RESULT = FN (*ARG0, *ARG1)

   in format FORMAT.  Return true on success.  */

static bool
fold_const_call_sss (real_value *result, built_in_function fn,
                     const real_value *arg0, const real_value *arg1,
                     const real_format *format)
{
  switch (fn)
    {
    CASE_FLT_FN (BUILT_IN_DREM):
    CASE_FLT_FN (BUILT_IN_REMAINDER):
      return do_mpfr_arg2 (result, mpfr_remainder, arg0, arg1, format);

    CASE_FLT_FN (BUILT_IN_ATAN2):
      return do_mpfr_arg2 (result, mpfr_atan2, arg0, arg1, format);

    CASE_FLT_FN (BUILT_IN_FDIM):
      return do_mpfr_arg2 (result, mpfr_dim, arg0, arg1, format);

    CASE_FLT_FN (BUILT_IN_HYPOT):
      return do_mpfr_arg2 (result, mpfr_hypot, arg0, arg1, format);

    CASE_FLT_FN (BUILT_IN_COPYSIGN):
      *result = *arg0;
      real_copysign (result, arg1);
      return true;

    CASE_FLT_FN (BUILT_IN_FMIN):
      return do_mpfr_arg2 (result, mpfr_min, arg0, arg1, format);

    CASE_FLT_FN (BUILT_IN_FMAX):
      return do_mpfr_arg2 (result, mpfr_max, arg0, arg1, format);

    CASE_FLT_FN (BUILT_IN_POW):
      return fold_const_pow (result, arg0, arg1, format);

    default:
      return false;
    }
}

/* Try to evaluate:

      *RESULT = FN (*ARG0, ARG1)

   where FORMAT is the format of *RESULT and *ARG0.  Return true on
   success.  */

static bool
fold_const_call_sss (real_value *result, built_in_function fn,
                     const real_value *arg0, const wide_int_ref &arg1,
                     const real_format *format)
{
  switch (fn)
    {
    CASE_FLT_FN (BUILT_IN_LDEXP):
      return fold_const_builtin_load_exponent (result, arg0, arg1, format);

    CASE_FLT_FN (BUILT_IN_SCALBN):
    CASE_FLT_FN (BUILT_IN_SCALBLN):
      return (format->b == 2
              && fold_const_builtin_load_exponent (result, arg0, arg1,
                                                   format));

    CASE_FLT_FN (BUILT_IN_POWI):
      real_powi (result, format, arg0, arg1.to_shwi ());
      return true;

    default:
      return false;
    }
}

/* Try to evaluate:

      *RESULT = FN (ARG0, *ARG1)

   where FORMAT is the format of *RESULT and *ARG1.  Return true on
   success.  */

static bool
fold_const_call_sss (real_value *result, built_in_function fn,
                     const wide_int_ref &arg0, const real_value *arg1,
                     const real_format *format)
{
  switch (fn)
    {
    CASE_FLT_FN (BUILT_IN_JN):
      return do_mpfr_arg2 (result, mpfr_jn, arg0, arg1, format);

    CASE_FLT_FN (BUILT_IN_YN):
      return (real_compare (GT_EXPR, arg1, &dconst0)
              && do_mpfr_arg2 (result, mpfr_yn, arg0, arg1, format));

    default:
      return false;
    }
}

/* Try to evaluate:

      RESULT = fn (ARG0, ARG1)

   where FORMAT is the format of the real and imaginary parts of RESULT
   (RESULT_REAL and RESULT_IMAG), of ARG0 (ARG0_REAL and ARG0_IMAG)
   and of ARG1 (ARG1_REAL and ARG1_IMAG).  Return true on success.  */

static bool
fold_const_call_ccc (real_value *result_real, real_value *result_imag,
                     built_in_function fn, const real_value *arg0_real,
                     const real_value *arg0_imag, const real_value *arg1_real,
                     const real_value *arg1_imag, const real_format *format)
{
  switch (fn)
    {
    CASE_FLT_FN (BUILT_IN_CPOW):
      return do_mpc_arg2 (result_real, result_imag, mpc_pow,
                          arg0_real, arg0_imag, arg1_real, arg1_imag, format);

    default:
      return false;
    }
}

/* Subroutine of fold_const_call, with the same interface.  Handle cases
   where the arguments and result are numerical.  */

static tree
fold_const_call_1 (built_in_function fn, tree type, tree arg0, tree arg1)
{
  machine_mode mode = TYPE_MODE (type);
  machine_mode arg0_mode = TYPE_MODE (TREE_TYPE (arg0));
  machine_mode arg1_mode = TYPE_MODE (TREE_TYPE (arg1));

  if (arg0_mode == arg1_mode
      && real_cst_p (arg0)
      && real_cst_p (arg1))
    {
      gcc_checking_assert (SCALAR_FLOAT_MODE_P (arg0_mode));
      if (mode == arg0_mode)
        {
          /* real, real -> real.  */
          REAL_VALUE_TYPE result;
          if (fold_const_call_sss (&result, fn, TREE_REAL_CST_PTR (arg0),
                                   TREE_REAL_CST_PTR (arg1),
                                   REAL_MODE_FORMAT (mode)))
            return build_real (type, result);
        }
      return NULL_TREE;
    }

  if (real_cst_p (arg0)
      && integer_cst_p (arg1))
    {
      gcc_checking_assert (SCALAR_FLOAT_MODE_P (arg0_mode));
      if (mode == arg0_mode)
        {
          /* real, int -> real.  */
          REAL_VALUE_TYPE result;
          if (fold_const_call_sss (&result, fn, TREE_REAL_CST_PTR (arg0),
                                   arg1, REAL_MODE_FORMAT (mode)))
            return build_real (type, result);
        }
      return NULL_TREE;
    }

  if (integer_cst_p (arg0)
      && real_cst_p (arg1))
    {
      gcc_checking_assert (SCALAR_FLOAT_MODE_P (arg1_mode));
      if (mode == arg1_mode)
        {
          /* int, real -> real.  */
          REAL_VALUE_TYPE result;
          if (fold_const_call_sss (&result, fn, arg0,
                                   TREE_REAL_CST_PTR (arg1),
                                   REAL_MODE_FORMAT (mode)))
            return build_real (type, result);
        }
      return NULL_TREE;
    }

  if (arg0_mode == arg1_mode
      && complex_cst_p (arg0)
      && complex_cst_p (arg1))
    {
      gcc_checking_assert (COMPLEX_MODE_P (arg0_mode));
      machine_mode inner_mode = GET_MODE_INNER (arg0_mode);
      tree arg0r = TREE_REALPART (arg0);
      tree arg0i = TREE_IMAGPART (arg0);
      tree arg1r = TREE_REALPART (arg1);
      tree arg1i = TREE_IMAGPART (arg1);
      if (mode == arg0_mode
          && real_cst_p (arg0r)
          && real_cst_p (arg0i)
          && real_cst_p (arg1r)
          && real_cst_p (arg1i))
        {
          /* complex real, complex real -> complex real.  */
          REAL_VALUE_TYPE result_real, result_imag;
          if (fold_const_call_ccc (&result_real, &result_imag, fn,
                                   TREE_REAL_CST_PTR (arg0r),
                                   TREE_REAL_CST_PTR (arg0i),
                                   TREE_REAL_CST_PTR (arg1r),
                                   TREE_REAL_CST_PTR (arg1i),
                                   REAL_MODE_FORMAT (inner_mode)))
            return build_complex (type,
                                  build_real (TREE_TYPE (type), result_real),
                                  build_real (TREE_TYPE (type), result_imag));
        }
      return NULL_TREE;
    }

  return NULL_TREE;
}

/* Try to fold FN (ARG0, ARG1) to a constant.  Return the constant on success,
   otherwise return null.  TYPE is the type of the return value.  */

tree
fold_const_call (built_in_function fn, tree type, tree arg0, tree arg1)
{
  const char *p0, *p1;
  switch (fn)
    {
    case BUILT_IN_STRSPN:
      if ((p0 = c_getstr (arg0)) && (p1 = c_getstr (arg1)))
        return build_int_cst (type, strspn (p0, p1));
      return NULL_TREE;

    case BUILT_IN_STRCSPN:
      if ((p0 = c_getstr (arg0)) && (p1 = c_getstr (arg1)))
        return build_int_cst (type, strcspn (p0, p1));
      return NULL_TREE;

    case BUILT_IN_STRCMP:
      if ((p0 = c_getstr (arg0)) && (p1 = c_getstr (arg1)))
        return build_cmp_result (type, strcmp (p0, p1));
      return NULL_TREE;

    default:
      return fold_const_call_1 (fn, type, arg0, arg1);
    }
}

/* Try to evaluate:

      *RESULT = FN (*ARG0, *ARG1, *ARG2)

   in format FORMAT.  Return true on success.  */

static bool
fold_const_call_ssss (real_value *result, built_in_function fn,
                      const real_value *arg0, const real_value *arg1,
                      const real_value *arg2, const real_format *format)
{
  switch (fn)
    {
    CASE_FLT_FN (BUILT_IN_FMA):
      return do_mpfr_arg3 (result, mpfr_fma, arg0, arg1, arg2, format);

    default:
      return false;
    }
}

/* Subroutine of fold_const_call, with the same interface.  Handle cases
   where the arguments and result are numerical.  */

static tree
fold_const_call_1 (built_in_function fn, tree type, tree arg0, tree arg1,
                   tree arg2)
{
  machine_mode mode = TYPE_MODE (type);
  machine_mode arg0_mode = TYPE_MODE (TREE_TYPE (arg0));
  machine_mode arg1_mode = TYPE_MODE (TREE_TYPE (arg1));
  machine_mode arg2_mode = TYPE_MODE (TREE_TYPE (arg2));

  if (arg0_mode == arg1_mode
      && arg0_mode == arg2_mode
      && real_cst_p (arg0)
      && real_cst_p (arg1)
      && real_cst_p (arg2))
    {
      gcc_checking_assert (SCALAR_FLOAT_MODE_P (arg0_mode));
      if (mode == arg0_mode)
        {
          /* real, real, real -> real.  */
          REAL_VALUE_TYPE result;
          if (fold_const_call_ssss (&result, fn, TREE_REAL_CST_PTR (arg0),
                                    TREE_REAL_CST_PTR (arg1),
                                    TREE_REAL_CST_PTR (arg2),
                                    REAL_MODE_FORMAT (mode)))
            return build_real (type, result);
        }
      return NULL_TREE;
    }

  return NULL_TREE;
}

/* Try to fold FN (ARG0, ARG1, ARG2) to a constant.  Return the constant on
   success, otherwise return null.  TYPE is the type of the return value.  */

tree
fold_const_call (built_in_function fn, tree type, tree arg0, tree arg1,
                 tree arg2)
{
  const char *p0, *p1;
  size_t s2;
  switch (fn)
    {
    case BUILT_IN_STRNCMP:
      if ((p0 = c_getstr (arg0))
          && (p1 = c_getstr (arg1))
          && host_size_t_cst_p (arg2, &s2))
        return build_int_cst (type, strncmp (p0, p1, s2));
      return NULL_TREE;

    case BUILT_IN_BCMP:
    case BUILT_IN_MEMCMP:
      if ((p0 = c_getstr (arg0))
          && (p1 = c_getstr (arg1))
          && host_size_t_cst_p (arg2, &s2)
          && s2 <= strlen (p0)
          && s2 <= strlen (p1))
        return build_cmp_result (type, memcmp (p0, p1, s2));
      return NULL_TREE;

    default:
      return fold_const_call_1 (fn, type, arg0, arg1, arg2);
    }
}

/* Fold a fma operation with arguments ARG[012].  */

tree
fold_fma (location_t, tree type, tree arg0, tree arg1, tree arg2)
{
  REAL_VALUE_TYPE result;
  if (real_cst_p (arg0)
      && real_cst_p (arg1)
      && real_cst_p (arg2)
      && do_mpfr_arg3 (&result, mpfr_fma, TREE_REAL_CST_PTR (arg0),
                       TREE_REAL_CST_PTR (arg1), TREE_REAL_CST_PTR (arg2),
                       REAL_MODE_FORMAT (TYPE_MODE (type))))
    return build_real (type, result);

  return NULL_TREE;
}