[Bug tree-optimization/66952] 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=66952

            Bug ID: 66952
           Summary: wrong code at -O2 and -O3 on x86_64-linux-gnu
           Product: gcc
           Version: 6.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: tree-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 at -O2 and
-O3 in both 32-bit and 64-bit modes. 

This is a regression from 5.1.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/6.0.0/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 6.0.0 20150719 (experimental) [trunk revision 225987] (GCC) 
$ 
$ gcc-trunk -Os small.c; ./a.out
$ gcc-5.1 -O2 small.c; ./a.out
$ 
$ gcc-trunk -O2 small.c
$ ./a.out
Aborted (core dumped)
$ 


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


int a = 128, b;

int
fn1 (char p1, int p2)
{
  return p1 < 0 || p1 > 1 >> p2 ? 0 : p1 << 1;
}

int
fn2 ()
{
  char c = a;
  b = fn1 (c, 1);
  if ((128 | c) < 0 ? 1 : 0)
    return 1;
  return 0;
}

int
main ()
{
  if (fn2 () != 1)
    __builtin_abort ();

  return 0;
}