[Bug rtl-optimization/71887] New: wrong code (SIGFPE) at -O1 and above on x86_64-linux-gnu (in both 32-bit and 64-bit modes)

[su at cs dot ucdavis.edu]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=71887

            Bug ID: 71887
           Summary: wrong code (SIGFPE) at -O1 and above on
                    x86_64-linux-gnu (in both 32-bit and 64-bit modes)
           Product: gcc
           Version: 7.0
            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 trunk miscompiles the following code on x86_64-linux-gnu at -O1
and above in both 32-bit and 64-bit modes.

This is a regression from 6.1.x. 


$ gcc-trunk -v
Using built-in specs.
COLLECT_GCC=gcc-trunk
COLLECT_LTO_WRAPPER=/usr/local/gcc-trunk/libexec/gcc/x86_64-pc-linux-gnu/7.0.0/lto-wrapper
Target: x86_64-pc-linux-gnu
Configured with: ../gcc-source-trunk/configure --enable-languages=c,c++,lto
--prefix=/usr/local/gcc-trunk --disable-bootstrap
Thread model: posix
gcc version 7.0.0 20160714 (experimental) [trunk revision 238331] (GCC) 
$ 
$ gcc-trunk -O0 small.c; ./a.out
$ gcc-6.1 -O1 small.c; ./a.out
$ 
$ gcc-trunk -O1 small.c
$ ./a.out
Floating point exception (core dumped)
$ 


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


char a;
int b;

int main ()
{
  unsigned char c = a, d = a;
  b = d == 0 ? c : c % d;
  return 0;
}