[Bug tree-optimization/67859] New: ICE on valid 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=67859

            Bug ID: 67859
           Summary: ICE on valid 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 following code causes an ICE when compiled with the current gcc trunk at
-O2 and -O3 on x86_64-linux-gnu in both 32-bit and 64-bit modes.

It 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 20151005 (experimental) [trunk revision 228480] (GCC) 
$ 
$ gcc-trunk -Os -c small.c
$ gcc-5.2 -O2 -c small.c
$ 
$ gcc-trunk -O2 -c small.c
small.c: In function ‘fn1’:
small.c:4:1: internal compiler error: Segmentation fault
 fn1 ()
 ^
0xaaf71f crash_signal
        ../../gcc-trunk/gcc/toplev.c:353
0xc5fdfa free_scc_vn()
        ../../gcc-trunk/gcc/tree-ssa-sccvn.c:3988
0xc4121f execute
        ../../gcc-trunk/gcc/tree-ssa-pre.c:4847
Please submit a full bug report,
with preprocessed source if appropriate.
Please include the complete backtrace with any bug report.
See <http://gcc.gnu.org/bugs.html> for instructions.
$ 


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


int a, b, c;

void
fn1 ()
{
  b = c ? 0 : 1 << a;
  b |= 0x9D7A5FD9;
  for (;;)
    {
      int d = 1;
      b &= (unsigned) d;
    }
}