[Bug tree-optimization/69292] New: ICE with -floop-nest-optimize

["vries at gcc dot gnu.org" <gcc-bugzilla at gcc dot gnu dot org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=69292

            Bug ID: 69292
           Summary: ICE with -floop-nest-optimize
           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: ---

Created attachment 37350
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=37350&action=edit
test-case pr39516.c

Attached test-case pr39516.c is:
- src/gcc/testsuite/gfortran.dg/graphite/pr39516.f
- rewritten to C, and 
- replaced the int *__restrict m function argument with a file-scope
  declared m[1] (to get a valid data-ref without the fix for PR69110)

When compiling with -floop-nest-optimize:
...
$ gcc pr39516.c -O2 -floop-nest-optimize -S
...

we run into:
...
pr39516.c: In function âfooâ:
pr39516.c:4:1: internal compiler error: Segmentation fault
 foo (double a[20][20], double b[20])
 ^~~

0xefb0cc crash_signal
        src/gcc/toplev.c:334
0xf62761 ssa_default_def(function*, tree_node*)
        src/gcc/tree-dfa.c:305
0xf62b08 get_or_create_ssa_default_def(function*, tree_node*)
        src/gcc/tree-dfa.c:357
0xfa9a21 get_reaching_def
        src/gcc/tree-into-ssa.c:1168
0xfaaf82 maybe_replace_use
        src/gcc/tree-into-ssa.c:1755
0xfab5c1 rewrite_update_stmt
        src/gcc/tree-into-ssa.c:1950
0xfabcf0 rewrite_update_dom_walker::before_dom_children(basic_block_def*)
        src/gcc/tree-into-ssa.c:2130
0x1c3a9a0 dom_walker::walk(basic_block_def*)
        src/gcc/domwalk.c:265
0xfabe35 rewrite_blocks
        src/gcc/tree-into-ssa.c:2194
0xfaeb45 update_ssa(unsigned int)
        src/gcc/tree-into-ssa.c:3356
0x1c75308 graphite_regenerate_ast_isl(scop*)
        src/gcc/graphite-isl-ast-to-gimple.c:3319
0x1c6c572 graphite_transform_loops()
        src/gcc/graphite.c:329
0x1c6c5f6 graphite_transforms
        src/gcc/graphite.c:356
0x1c6c719 execute
        src/gcc/graphite.c:433
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with preprocessed source if appropriate.
Please include the complete backtrace with any bug report.
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