Only run compute_dominators etc when the optimize flag is set; we don't need them otherwise, and also there's a bug in compute_dominance_frontiers (#38264).
Only run compute_dominators etc when the optimize flag is set; we don't need them otherwise, and also there's a bug in compute_dominance_frontiers (#38264).

git-svn-id: 6e74a02f85675cec270f5d931b0f6998666294a3@11238 d31e2699-5ff4-0310-a27c-f18f2fbe73fe

ashgti/parrot,ashgti/parrot,ashgti/parrot,ashgti/parrot,ashgti/parrot,ashgti/parrot,ashgti/parrot