[Bug tree-optimization/69108] New: ICE in gather_scalar_reductions with -ftree-parallelize-loops=2

[vries at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=69108

            Bug ID: 69108
           Summary: ICE in gather_scalar_reductions with
                    -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: vries at gcc dot gnu.org
  Target Milestone: ---

...
$ gcc -O2 src/gcc/testsuite/gcc.dg/graphite/interchange-2.c -S
-ftree-parallelize-loops=2 
src/gcc/testsuite/gcc.dg/graphite/interchange-2.c: In function ‘foo.constprop’:
src/gcc/testsuite/gcc.dg/graphite/interchange-2.c:13:1: internal compiler
error: in as_a, at is-a.h:192
 foo (int N, int *res)
 ^~~

0x89e14b gphi* as_a<gphi*, gimple>(gimple*)
        /home/vries/gcc_versions/devel/src/gcc/is-a.h:192
0xfd7915 gather_scalar_reductions
        /home/vries/gcc_versions/devel/src/gcc/tree-parloops.c:2477
0xfd7c4c try_create_reduction_list
        /home/vries/gcc_versions/devel/src/gcc/tree-parloops.c:2549
0xfd8542 parallelize_loops
        /home/vries/gcc_versions/devel/src/gcc/tree-parloops.c:2726
0xfd8835 execute
        /home/vries/gcc_versions/devel/src/gcc/tree-parloops.c:2797
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...