[Bug tree-optimization/59014] New: wrong code at -Os and above on x86_64-linux-gnu

[su at cs dot ucdavis.edu]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=59014

            Bug ID: 59014
           Summary: wrong code at -Os and above on x86_64-linux-gnu
           Product: gcc
           Version: 4.9.0
            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-gnu at -Os
and above in both 32-bit and 64-bit modes. 

This is a regression from 4.8.x.

$ 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 20131105 (experimental) [trunk revision 204388] (GCC) 
$ 
$ gcc-trunk -O1 small.c; a.out
2
$ gcc-4.8.2 -Os small.c; a.out
2
$ gcc-trunk -Os small.c; a.out
0
$ 
$ 


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


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

int a = 2, b, c, d;

int
foo ()
{
  for (;; c++)
    if ((b > 0) | (a & 1))
      ;
    else
      {
    d = a;
    return 0;
      }
}

int
main ()
{
  foo ();
  printf ("%d\n", d);
  return 0;
}