[Bug c/82775] New: int += float different from int = int + float on Intel x87

[tydeman at tybor dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=82775

            Bug ID: 82775
           Summary: int += float different from int = int + float on Intel
                    x87
           Product: gcc
           Version: unknown
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c
          Assignee: unassigned at gcc dot gnu.org
          Reporter: tydeman at tybor dot com
  Target Milestone: ---

/* 
 * 3 different answers from 4 "same" expressions for Intel x87 (not sse2).
 * 55555580 55555556 55555581 55555581
 * CFLAGS="-H -std=gnu11 -O0 -march=native -mfpmath=387 -mieee-fp -fno-builtin
-frounding-math -ffloat-store -fexcess-precision=standard -fsignaling-nans"
 */

#include <stdio.h>

int main(void){
  int i1 = 0x55555555;
  int i2 = 0x55555555;
  int i3 = 0x55555555;
  int i4 = 0x55555555;
  float one = 1.f;

  i1 += one;
  i2 += 1.f;
  i3 = i3 + one;
  i4 = i4 + 1.f;
  (void)printf("%x %x %x %x\n", i1, i2, i3, i4);

  return 0;
}