https://gcc.gnu.org/bugzilla/show_bug.cgi?id=63155
--- Comment #2 from Richard Biener <rguenth at gcc dot gnu.org> --- I wonder why we need to explicitely represent abnormal PHIs in the dispatcher. All incoming edges are abnormal and all SSA names have to be coalesced anyway. Thus we could instead have <bb 5>: /* Not: # _2(ab) = PHI <_17(D)(ab)(2), _1(ab)(6), _1(ab)(7), _3(ab)(11), _3(ab)(12), _4(ab)(15), _4(ab)(16), _5(ab)(20), _5(ab)(21), _5(ab)(22)> */ ABNORMAL_DISPATCHER (0); _2(ab) = D.12345; or simply rewrite all must-coalesce vars out-of-SSA? (or not into SSA in the first place) The question is whether accesses to them should be loads/stores (I think so) and if that will cause other similar issues. We'd have to factor abnormal edges into a block to a separate forwarder of course, with a load of all "abnormal" vars. Anyway, not sure why the gimplify code is disabled for -O0 (or why we don't re-use formal temps more aggressively as they become anonymous SSA names later anyway).
