https://gcc.gnu.org/bugzilla/show_bug.cgi?id=79347
--- Comment #3 from Jan Hubicka <hubicka at gcc dot gnu.org> --- Further work needed. I did not fix the actual issue in vectorizer because I am really lost in the new prologue code. I hope Bin will chime in and help me ;) The situation is not that bad overall, but it could be significantly better ;) For tramp3d the mismatch count looks as follows: tramp.ii.156t.ch_vect 185 tramp.ii.157t.ifcvt 267 tramp.ii.158t.vect 1076 ... tramp.ii.226t.optimized 888 the increase from 185 to 267 are the fake mismatches that should go away after folding, so vectorizer itself introduce about 800 new errors. On gcc 6 the scores are: tramp3d-v4.cpp.146t.ch_vect 331 tramp3d-v4.cpp.147t.ifcvt 331 tramp3d-v4.cpp.148t.vect 1050 .... tramp3d-v4.cpp.211t.optimized 1039 So the overall mismatch count is worse, but vectorizer is somewhat less disturbing. The main reason for decrease of mismatch count is stronger early opts. On mainline I get: tramp.ii.091t.ccp2 0 tramp.ii.093t.cunrolli 17 tramp.ii.094t.backprop 17 tramp.ii.095t.phiprop 17 tramp.ii.096t.forwprop2 17 tramp.ii.097t.objsz2 17 tramp.ii.098t.alias 17 tramp.ii.099t.retslot 17 tramp.ii.100t.fre3 42 tramp.ii.101t.mergephi2 40 tramp.ii.102t.thread1 98 tramp.ii.103t.vrp1 265 tramp.ii.105t.dce2 169 while gcc 6 gets: tramp3d-v4.cpp.084t.oaccdevlow 0 tramp3d-v4.cpp.086t.ccp2 0 tramp3d-v4.cpp.087t.cunrolli 23 tramp3d-v4.cpp.088t.backprop 23 tramp3d-v4.cpp.089t.phiprop 23 tramp3d-v4.cpp.090t.forwprop2 23 tramp3d-v4.cpp.091t.objsz2 23 tramp3d-v4.cpp.092t.alias 23 tramp3d-v4.cpp.093t.retslot 23 tramp3d-v4.cpp.094t.fre3 31 tramp3d-v4.cpp.095t.mergephi2 29 tramp3d-v4.cpp.096t.vrp1 466 tramp3d-v4.cpp.098t.dce2 426 Report on vrp1 itself is wrong because it dumps bbs multiple times, but clearly vrp1+thread1 now introduce a lot fewer problems than vrp1 in gcc 6. Most of those mismatches are justified becuase we prove some branches with non-0 probability to be impossible or we thread in a way contradicting profile. Honza
