[Bug tree-optimization/69652] New: [6 Regression] [ICE] verify_ssa fail w/ -O2 -ffast-math -ftree-vectorize

[kyukhin at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=69652

            Bug ID: 69652
           Summary: [6 Regression] [ICE] verify_ssa fail w/ -O2
                    -ffast-math -ftree-vectorize
           Product: gcc
           Version: 6.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: tree-optimization
          Assignee: unassigned at gcc dot gnu.org
          Reporter: kyukhin at gcc dot gnu.org
  Target Milestone: ---

Created attachment 37569
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=37569&action=edit
Reproducer

While building huge workload I've encountered ICE.
creduce finished w/ attached reproducer.

Reproduce:
$ ./gcc -O2 -ffast-math -ftree-vectorize -march=sandybridge repro.i
repro.i:1:1: warning: return type defaults to ‘int’ [-Wimplicit-int]
 fn1() {
 ^~~
repro.i: In function ‘fn1’:
repro.i:1:1: error: definition in block 8 does not dominate use in block 7
for SSA_NAME: .MEM_134 in statement:
# VUSE <.MEM_134>
_24 = *_13;
repro.i:1:1: internal compiler error: verify_ssa failed
0xd12f09 verify_ssa(bool, bool)
        /export/users/kyukhin/gcc/git/gcc/gcc/tree-ssa.c:1039
0xa52dad execute_function_todo
        /export/users/kyukhin/gcc/git/gcc/gcc/passes.c:1965
0xa5363b execute_todo
        /export/users/kyukhin/gcc/git/gcc/gcc/passes.c:2010
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.

Recent gcc-5-branch works fine w/ the case