[Bug tree-optimization/69426] New: [6 Regression] ICE: verify_ssa failed (error: missing definition) w/ -O2 (and above) -ftree-parallelize-loops=2

["asolokha at gmx dot com" <gcc-bugzilla at gcc dot gnu dot org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=69426

            Bug ID: 69426
           Summary: [6 Regression] ICE: verify_ssa failed (error: missing
                    definition) w/ -O2 (and above)
                    -ftree-parallelize-loops=2
           Product: gcc
           Version: 6.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: tree-optimization
          Assignee: unassigned at gcc dot gnu.org
          Reporter: asolokha at gmx dot com
                CC: vries at gcc dot gnu.org
  Target Milestone: ---

At least gcc-6.0.0-alpha20160110 and gcc-6.0.0-alpha20160117 snapshots ICE when
compiling the following reduced snippet w/ -O2 (-O3, -Ofast)
-ftree-parallelize-loops=2:

int iq;

void
mr(void)
{
  unsigned int i8;

  for (i8 = 0; i8 != 1; i8 += 3) {
    void *f0[] = { f0 };
    int hv;

    for (; hv < 1; ++hv)
      iq = 0;
  }
  ++iq;
}

% gcc-6.0.0-alpha20160117 -c -O2 -ftree-parallelize-loops=2 nmrq2xcy.c -Wall
-Wextra -Wpedantic
nmrq2xcy.c: In function 'mr':
nmrq2xcy.c:4:1: error: missing definition
 mr(void)
 ^~

for SSA_NAME: .MEM_11 in statement:
.MEM_2 = PHI <.MEM_11(17), .MEM_7(D)(15)>
PHI argument
.MEM_11
for PHI node
.MEM_2 = PHI <.MEM_11(17), .MEM_7(D)(15)>
nmrq2xcy.c:4:1: internal compiler error: verify_ssa failed