[Bug tree-optimization/71366] New: ICE on valid code at -O3 on x86_64-linux-gnu: Segmentation fault

[su at cs dot ucdavis.edu]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=71366

            Bug ID: 71366
           Summary: ICE on valid code at -O3 on x86_64-linux-gnu:
                    Segmentation fault
           Product: gcc
           Version: 7.0
            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
-O3 on x86_64-linux-gnu in both 32-bit and 64-bit modes.

It is a regression from 6.1.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/7.0.0/lto-wrapper
Target: x86_64-pc-linux-gnu
Configured with: ../gcc-source-trunk/configure --enable-languages=c,c++,lto
--prefix=/usr/local/gcc-trunk --disable-bootstrap
Thread model: posix
gcc version 7.0.0 20160531 (experimental) [trunk revision 236912] (GCC)
$
$ gcc-trunk -O2 -c small.c
$ gcc-6.1 -O3 -c small.c
$
$ gcc-trunk -O3 -c small.c
small.c: In function ‘fn1’:
small.c:4:1: internal compiler error: Segmentation fault
 fn1 ()
 ^~~
0xbbd02f crash_signal
        ../../gcc-source-trunk/gcc/toplev.c:333
0xd08d70 vec_safe_length<loop*, va_gc>
        ../../gcc-source-trunk/gcc/vec.h:529
0xd08d70 loop_outer
        ../../gcc-source-trunk/gcc/cfgloop.h:456
0xd08d70 tree_unroll_loops_completely_1
        ../../gcc-source-trunk/gcc/tree-ssa-loop-ivcanon.c:1347
0xd08ce0 tree_unroll_loops_completely_1
        ../../gcc-source-trunk/gcc/tree-ssa-loop-ivcanon.c:1314
0xd08ce0 tree_unroll_loops_completely_1
        ../../gcc-source-trunk/gcc/tree-ssa-loop-ivcanon.c:1314
0xd09013 tree_unroll_loops_completely(bool, bool)
        ../../gcc-source-trunk/gcc/tree-ssa-loop-ivcanon.c:1384
0xd09583 execute
        ../../gcc-source-trunk/gcc/tree-ssa-loop-ivcanon.c:1593
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[1][2], b, c;

int
fn1 ()
{ 
  int d;
  for (; c;)
    for (d = 2; d >= 0;)
      { 
        int e[4], f = e[3];
        if (f)
          return b;
        d--;
        for (;;)
          { 
            c = a[0][d];
            break;
          }
      }
  return 0;
}