[Bug tree-optimization/61197] New: wrong code at -O3 on x86_64-linux (in both 32-bit and 64-bit modes)

[su at cs dot ucdavis.edu]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=61197

            Bug ID: 61197
           Summary: wrong code at -O3 on x86_64-linux (in both 32-bit and
                    64-bit modes)
           Product: gcc
           Version: 4.10.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: tree-optimization
          Assignee: unassigned at gcc dot gnu.org
          Reporter: su at cs dot ucdavis.edu

The current gcc trunk miscompiles the following code on x86_64-linux at -O3 in
both 32-bit and 64-bit modes.  

This is a regression from 4.9.x. 

It seems different from PR 61140 and PR 61150 as -fno-tree-dce makes both
disappear, but not this one. 

$ gcc-trunk -v
Using built-in specs.
COLLECT_GCC=gcc-trunk
COLLECT_LTO_WRAPPER=/usr/local/gcc-trunk/libexec/gcc/x86_64-unknown-linux-gnu/4.10.0/lto-wrapper
Target: x86_64-unknown-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 4.10.0 20140515 (experimental) [trunk revision 210458] (GCC) 
$ 
$ gcc-trunk -O2 small.c; a.out
$ gcc-4.9.0 -O3 small.c; a.out
$ 
$ gcc-trunk -O3 small.c; a.out
Aborted (core dumped)
$


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


int a, b = 1, *c = &a; 

int
foo ()
{
  if (b)
    b |= 1;
  else
    {
      b = 1;
      return 0;
    }
  return 1;
}

int
main ()
{
  *c = foo ();
  if (a != 1) 
    __builtin_abort (); 
  return 0;
}