[Bug tree-optimization/82337] New: -O2: ICE: SSA corruption at tree-ssa-coalesce.c:1010

[ivo.raisr at oracle dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=82337

            Bug ID: 82337
           Summary: -O2: ICE: SSA corruption at tree-ssa-coalesce.c:1010
           Product: gcc
           Version: 8.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: tree-optimization
          Assignee: unassigned at gcc dot gnu.org
          Reporter: ivo.raisr at oracle dot com
  Target Milestone: ---

With gcc 8.0, 7.2 and 6.3.1 we hit internal compiler error:

Unable to coalesce ssa_names 7 and 15 which are marked as MUST COALESCE.
i_7(ab) and  i_15(ab)
during RTL pass: expand
reduced-3.c:12:6: internal compiler error: SSA corruption
 void g(void) {
      ^
0xe24c8c fail_abnormal_edge_coalesce
        ../../gcc-trunk/gcc/tree-ssa-coalesce.c:1010
0xe24c8c coalesce_partitions
        ../../gcc-trunk/gcc/tree-ssa-coalesce.c:1399
0xe24c8c coalesce_ssa_name()
        ../../gcc-trunk/gcc/tree-ssa-coalesce.c:1886
0xdca93b remove_ssa_form
        ../../gcc-trunk/gcc/tree-outof-ssa.c:948
0xdca93b rewrite_out_of_ssa(ssaexpand*)
        ../../gcc-trunk/gcc/tree-outof-ssa.c:1172
0x992d70 execute
        ../../gcc-trunk/gcc/cfgexpand.c:6164


Full pre-processed sources are not publicly available.

C-reduce was able to produce "reduced-3.bare.c" which I slightly reformatted to
make it more readable: "reduced-3.c". Both files attached.

Reproduce as:
$ gcc -c reduced-3.c -O2