[PATCH] PR middle-end/53267: Constant fold BUILT_IN_FMOD.

[Roger Sayle]

Here's a three line patch to implement constant folding for fmod,
fmodf and fmodl, which resolves an enhancement request from 2012.

The following patch has been tested on x86_64-pc-linux-gnu with
a make bootstrap and make -k check with no new failures.

Ok for mainline?


2020-06-08  Roger Sayle  <ro...@nextmovesoftware.com>

gcc/ChangeLog
        PR middle-end/53267
        * fold-const-call.c (fold_const_call_sss) [CASE_CFN_FMOD]:
        Support evaluation of fmod/fmodf/fmodl at compile-time.

gcc/testsuite/ChangeLog
        * gcc.dg/builtins-70.c: New test.


Roger
--
Roger Sayle
NextMove Software
Cambridge, UK


diff --git a/gcc/fold-const-call.c b/gcc/fold-const-call.c
index a1d70b6..d6cb9b1 100644
--- a/gcc/fold-const-call.c
+++ b/gcc/fold-const-call.c
@@ -1375,6 +1375,9 @@ fold_const_call_sss (real_value *result, combined_fn fn,
     CASE_CFN_FDIM:
       return do_mpfr_arg2 (result, mpfr_dim, arg0, arg1, format);
 
+    CASE_CFN_FMOD:
+      return do_mpfr_arg2 (result, mpfr_fmod, arg0, arg1, format);
+
     CASE_CFN_HYPOT:
       return do_mpfr_arg2 (result, mpfr_hypot, arg0, arg1, format);
 

/* Copyright (C) 2021 Free Software Foundation.

   Check that constant folding of built-in fmod functions doesn't
   break anything and produces the expected results.

/* { dg-do link } */
/* { dg-options "-O2 -ffast-math" } */

extern void link_error(void);

extern double fmod(double,double);
extern float fmodf(float,float);
extern long double fmodl(long double,long double);

int main()
{
  if (fmod (6.5, 2.3) < 1.8999 || fmod (6.5, 2.3) > 1.9001)
    link_error ();
  if (fmod (-6.5, 2.3) < -1.9001 || fmod (-6.5, 2.3) > -1.8999)
    link_error ();
  if (fmod (6.5, -2.3) < 1.8999 || fmod (6.5, -2.3) > 1.9001)
    link_error ();
  if (fmod (-6.5, -2.3) < -1.9001 || fmod (-6.5, -2.3) > -1.8999)
    link_error ();

  if (fmodf (6.5f, 2.3f) < 1.8999f || fmodf (6.5f, 2.3f) > 1.9001f)
    link_error ();
  if (fmodf (-6.5f, 2.3f) < -1.9001f || fmodf (-6.5f, 2.3f) > -1.8999f)
    link_error ();
  if (fmodf (6.5f, -2.3f) < 1.8999f || fmodf (6.5f, -2.3f) > 1.9001f)
    link_error ();
  if (fmodf (-6.5f, -2.3f) < -1.9001f || fmodf (-6.5f, -2.3f) > -1.8999f)
    link_error ();

  if (fmodl (6.5l, 2.3l) < 1.8999l || fmod (6.5l, 2.3l) > 1.9001l)
    link_error ();
  if (fmodl (-6.5l, 2.3l) < -1.9001l || fmod (-6.5l, 2.3l) > -1.8999l)
    link_error ();
  if (fmodl (6.5l, -2.3l) < 1.8999l || fmod (6.5l, -2.3l) > 1.9001l)
    link_error ();
  if (fmodl (-6.5l, -2.3l) < -1.9001l || fmod (-6.5l, -2.3l) > -1.8999l)
    link_error ();

  return 0;
}