[Bug rtl-optimization/68755] New: wrong code at -O3 on x86_64-linux-gnu (in 32-bit mode)

[su at cs dot ucdavis.edu]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=68755

            Bug ID: 68755
           Summary: wrong code at -O3 on x86_64-linux-gnu (in 32-bit mode)
           Product: gcc
           Version: 5.3.1
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: rtl-optimization
          Assignee: unassigned at gcc dot gnu.org
          Reporter: su at cs dot ucdavis.edu
  Target Milestone: ---

The current gcc 5 branch miscompiles the following code on x86_64-linux-gnu at
-O3 in the 32-bit mode (but not in the 64-bit mode). 

It does not seem to impact the mainline. 


$ gcc-5-branch -v
Using built-in specs.
COLLECT_GCC=gcc-5-branch
COLLECT_LTO_WRAPPER=/usr/local/gcc-5.3.1-branch/bin/../libexec/gcc/x86_64-unknown-linux-gnu/5.3.1/lto-wrapper
Target: x86_64-unknown-linux-gnu
Configured with: ../gcc-5.3-branch/configure --enable-languages=c,c++
Thread model: posix
gcc version 5.3.1 20151206 [gcc-5-branch revision 231343] (GCC) 
$ 
$ gcc-5-branch -m32 -O2 small.c; ./a.out
$ gcc-5-branch -m64 -O3 small.c; ./a.out
$ gcc-trunk -m32 -O3 small.c; ./a.out
$ 
$ gcc-5-branch -m32 -O3 small.c
$ ./a.out
Segmentation fault (core dumped)
$ 


---------------------------------------


int printf (const char *, ...);

int a, b;
short c, d;

int
main ()
{
  char e[5];
  for (; c < 5; c++)
    {
      while (a)
        {
          b = d;
          if (e[8000])
            continue;
          break;
        }
      if (b)
        printf ("%d", a);
    }
  return 0;
}