[Bug rtl-optimization/67786] New: wrong code at -O2 and -O3 on x86_64-linux-gnu

[su at cs dot ucdavis.edu]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=67786

            Bug ID: 67786
           Summary: wrong code at -O2 and -O3 on x86_64-linux-gnu
           Product: gcc
           Version: 6.0
            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 -O2
and -O3 in both 32-bit and 64-bit modes. 

This is a regression from 5.2.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/6.0.0/lto-wrapper
Target: x86_64-pc-linux-gnu
Configured with: ../gcc-trunk/configure --prefix=/usr/local/gcc-trunk
--enable-languages=c,c++ --disable-werror --enable-multilib
Thread model: posix
gcc version 6.0.0 20150930 (experimental) [trunk revision 228291] (GCC) 
$ 
$ gcc-trunk -Os small.c; ./a.out
15
$ gcc-5.2 -O2 small.c; ./a.out
15
$ 
$ gcc-trunk -O2 small.c; ./a.out
-32
$ 
$ 


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


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

int a, b = 10;
char c;

int
main ()
{
  char d;
  int e = 5;
  for (a = 0; a; a--)
    e = 0;
  c = (b & 15) ^ e;
  d = c > e ? c : c << e;
  printf ("%d\n", d);
  return 0;
}