[Bug rtl-optimization/58779] New: wrong code at -O1 on x86_64-linux-gnu

["su at cs dot ucdavis.edu" <gcc-bugzilla@gcc.gnu.org>]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=58779

            Bug ID: 58779
           Summary: wrong code at -O1 on x86_64-linux-gnu
           Product: gcc
           Version: 4.9.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: rtl-optimization
          Assignee: unassigned at gcc dot gnu.org
          Reporter: su at cs dot ucdavis.edu

The current gcc trunk (as well as gcc 4.7 and 4.8) miscompiles the following
code on x86_64-linux at -O1 in both 32-bit and 64-bit modes. 

This is a regression from 4.6.x. 

It disappears with -fno-if-conversion. 


$ 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/4.9.0/lto-wrapper
Target: x86_64-unknown-linux-gnu
Configured with: ../gcc-trunk/configure
--enable-languages=c,c++,objc,obj-c++,fortran,lto --disable-werror
--enable-checking=release --with-gmp=/usr/local/gcc-trunk
--with-mpfr=/usr/local/gcc-trunk --with-mpc=/usr/local/gcc-trunk
--with-cloog=/usr/local/gcc-trunk --prefix=/usr/local/gcc-trunk
Thread model: posix
gcc version 4.9.0 20131017 (experimental) [trunk revision 203789] (GCC) 
$ 
$ gcc-trunk -O0 small.c; a.out
$ 
$ gcc-trunk -O1 small.c; a.out
Aborted (core dumped)
$ 
$ gcc-trunk -O1 -fno-if-conversion small.c; a.out
$ 
$ gcc-4.8 -O1 small.c; a.out
Aborted (core dumped)
$
$ gcc-4.7 -O1 small.c; a.out
Aborted (core dumped)
$ 
$ gcc-4.6 -O1 small.c; a.out
$ 


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


int a, c;

int
main ()
{
  int e = -1;
  short d = (c <= 0) ^ e;
  if ((unsigned int) a - (a || d) <= (unsigned int) a)
    __builtin_abort(); 
  return 0;
}