[Bug tree-optimization/71341] New: ICE at -O2 and -O3 in 32-bit and 64-bit modes on x86_64-linux-gnu (Segmentation fault, duplicate_thread_path)

["chengniansun at gmail dot com" <gcc-bugzilla at gcc dot gnu dot org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=71341

            Bug ID: 71341
           Summary: ICE at -O2 and -O3 in 32-bit and 64-bit modes on
                    x86_64-linux-gnu (Segmentation fault,
                    duplicate_thread_path)
           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: ---

The following code crashes the trunk at -O2 and -O3 in 32-bit and 64-bit modes
on x86_64-linux-gnu.


$: 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 20160529 (experimental) [trunk revision 236861] (GCC) 
$: gcc-trunk -O2 small.c
small.c: In function âfn1â:
small.c:5:6: internal compiler error: Segmentation fault
 void fn1() {
      ^~~
0xbbc95f crash_signal
        ../../gcc-source-trunk/gcc/toplev.c:333
0xdbffac duplicate_thread_path
        ../../gcc-source-trunk/gcc/tree-ssa-threadupdate.c:2348
0xdbffac thread_through_all_blocks(bool)
        ../../gcc-source-trunk/gcc/tree-ssa-threadupdate.c:2496
0xdb8bee execute
        ../../gcc-source-trunk/gcc/tree-ssa-threadbackward.c:686
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
struct S3 {
  char f0;
};
int a, b;
void fn1() {
  struct S3 c = {1};
  while (!c.f0 || a) {
    c.f0 = 0;
    for (; c.f0; c.f0 = b)
      ;
  }
}

int main() {}
$: