[Bug tree-optimization/82276] New: -O2: ICE: SSA corruption during RTL pass: expand; at tree-ssa-coalesce.c:1010

[ivo.raisr at oracle dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=82276

            Bug ID: 82276
           Summary: -O2: ICE: SSA corruption during RTL pass: expand; at
                    tree-ssa-coalesce.c:1010
           Product: gcc
           Version: c++-concepts
            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 (SVN revision 252973 from 2017-09-19) we hit internal compiler
error:


Unable to coalesce ssa_names 8 and 28 which are marked as MUST COALESCE.
f_8(ab) and  f_28(ab)
during RTL pass: expand
reduced-2.c:12:6: internal compiler error: SSA corruption
 void c(void) {
      ^
0xe23c9c fail_abnormal_edge_coalesce
        ../../gcc-trunk/gcc/tree-ssa-coalesce.c:1010
0xe23c9c coalesce_partitions
        ../../gcc-trunk/gcc/tree-ssa-coalesce.c:1399
0xe23c9c coalesce_ssa_name()
        ../../gcc-trunk/gcc/tree-ssa-coalesce.c:1886
0xdc997b remove_ssa_form
        ../../gcc-trunk/gcc/tree-outof-ssa.c:948
0xdc997b rewrite_out_of_ssa(ssaexpand*)
        ../../gcc-trunk/gcc/tree-outof-ssa.c:1172
0x992a90 execute
        ../../gcc-trunk/gcc/cfgexpand.c:6164


Full pre-processed source is not publicly available but it is the same one as
for bug #82244.

C-reduce was able to produce "reduced-2.bare.c" which I slightly reformatted to
make it more readable: "reduced-2.c". Both files attached.

Reproduce as:
$ gcc -c reduced-2.c -O2