[Bug tree-optimization/71359] New: ICE at -Os and above in 32-bit and 64-bit modes on x86_64-linux-gnu (Segmentation fault, vec_safe_length<loop*, va_gc>)

[chengniansun at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=71359

            Bug ID: 71359
           Summary: ICE at -Os and above in 32-bit and 64-bit modes on
                    x86_64-linux-gnu (Segmentation fault,
                    vec_safe_length<loop*, va_gc>)
           Product: gcc
           Version: 7.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: tree-optimization
          Assignee: unassigned at gcc dot gnu.org
          Reporter: chengniansun at gmail dot com
  Target Milestone: ---

$: 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 -w -O3 small.c
small.c: In function ‘fn1’:
small.c:3:6: internal compiler error: Segmentation fault
 void 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.
$: cat small.c
char a[];
int b;
void fn1() {
  int i;
  for (;;) {
    i = 0;
    for (; i < 6; i++) {
      if (b)
        for (;;)
          ;
      int c = a[i];
      printf("", i);
    }
  }
}

int main() {}
$: