[Bug tree-optimization/78455] New: [7 Regression] ICE in operator[], at vec.h:732

[asolokha at gmx dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=78455

            Bug ID: 78455
           Summary: [7 Regression] ICE in operator[], at vec.h:732
           Product: gcc
           Version: 7.0
            Status: UNCONFIRMED
          Keywords: ice-on-valid-code
          Severity: normal
          Priority: P3
         Component: tree-optimization
          Assignee: unassigned at gcc dot gnu.org
          Reporter: asolokha at gmx dot com
                CC: aldyh at gcc dot gnu.org
  Target Milestone: ---

gcc-7.0.0-alpha20161120 snapshot fails to compile the following reduced snippet
w/ -O2 (-Os, -Og) -Wuninitialized:

int ij;

void
ql (void)
{
  int m5 = 0;

  for (;;)
  {
    if (0)
      for (;;)
      {
        int *go;
        int *t4 = go;

 l1:
        *t4 = (*t4 != 0) ? 0 : 2;
      }

    if (ij != 0)
      goto l1;
  }
}

% x86_64-unknown-linux-gnu-gcc-7.0.0-alpha20161120 -O2 -Wuninitialized -c
dwgke5h1.c
dwgke5h1.c: In function 'ql':
dwgke5h1.c:4:1: internal compiler error: in operator[], at vec.h:732
 ql (void)
 ^~

r242639 must be a culprit, given that the top of backtrace is this:

Breakpoint 1, 0x00000000013a3db0 in internal_error(char const*, ...) ()
(gdb) where
#0  0x00000000013a3db0 in internal_error(char const*, ...) ()
#1  0x00000000013a22c4 in fancy_abort(char const*, int, char const*) ()
#2  0x0000000000d8e861 in uninit_ops_invalidate_phi_use(gphi*, unsigned int,
vec<vec<pred_info, va_heap, vl_ptr>, va_heap, vl_ptr>) ()

<snip>