[Bug middle-end/68339] New: g++.dg/vect/simd-clone-2.cc ICEs with aggressive GC settings and OpenMP

[jason at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=68339

            Bug ID: 68339
           Summary: g++.dg/vect/simd-clone-2.cc ICEs with aggressive GC
                    settings and OpenMP
           Product: gcc
           Version: 6.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: middle-end
          Assignee: unassigned at gcc dot gnu.org
          Reporter: jason at gcc dot gnu.org
                CC: jakub at gcc dot gnu.org
  Target Milestone: ---

Compiling g++.dg/vect/simd-clone-2.cc with

  --param ggc-min-heapsize=0 --param ggc-min-expand=0 -fopenmp-simd

results in a memory corruption ICE.  This seems to be because
expand_simd_clones calls simd_clone_mangle, which generates an identifier, and
then calls simd_clone_create, which eventually calls ggc_collect from
execute_one_ipa_transform_pass.

Since nothing refers to the identifier yet, it gets collected as garbage, so
when expand_simd_clones tries to use it the compiler blows up.