[Bug tree-optimization/66856] New: [6 Regression] ICE in compute_live_loop_exits, at tree-ssa-loop-manip.c:234

[marxin at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=66856

            Bug ID: 66856
           Summary: [6 Regression] ICE in compute_live_loop_exits, at
                    tree-ssa-loop-manip.c:234
           Product: gcc
           Version: 6.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: tree-optimization
          Assignee: unassigned at gcc dot gnu.org
          Reporter: marxin at gcc dot gnu.org
  Target Milestone: ---

Created attachment 35966
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=35966&action=edit
vectorizer dump

Firefox built with -flto and -O3 produces following ICE:

/home/marxin/Programming/gecko-dev/gfx/cairo/libpixman/src/pixman-fast-path.c:
In function ‘fast_write_back_r5g6b5’:
/home/marxin/Programming/gecko-dev/gfx/cairo/libpixman/src/pixman-fast-path.c:2459:1:
internal compiler error: in compute_live_loop_exits, at
tree-ssa-loop-manip.c:234
 fast_write_back_r5g6b5 (pixman_iter_t *iter)
 ^
0xc8ed62 compute_live_loop_exits
        ../../gcc/tree-ssa-loop-manip.c:234
0xc8ed62 add_exit_phis_var
        ../../gcc/tree-ssa-loop-manip.c:321
0xc8ed62 add_exit_phis
        ../../gcc/tree-ssa-loop-manip.c:343
0xc8ed62 rewrite_into_loop_closed_ssa(bitmap_head*, unsigned int)
        ../../gcc/tree-ssa-loop-manip.c:538
0xd87283 vectorize_loops()
        ../../gcc/tree-vectorizer.c:586

Unfortunately, as it's a ltrans issue, it won't be hard to come up with a small
reproducer.

Thus, I attached vectorizer dump file, hope it will help.

Thanks,
Martin