[PATCH] D49569: [X86] Remove what appear to be unnecessary uses of DCI.CombineTo

[Craig Topper via Phabricator via llvm-commits]

craig.topper added a comment.

I ran vector-shuffle-combining.ll with and without the patch with debug output. I got a less visits of things after this patch. It looks like the normal worklist management aggressively removes N and recursively all of its children using DAGCombiner::recursivelyDeleteUnusedNodes. CombineTo on the other hand just puts all the children of N in the Worklist and assumes they'll be deleted if necessary when they get visited. So depending on what's in the worklist some nodes might get visited before the process has gotten a chance to propagate the deadness up the graph.


https://reviews.llvm.org/D49569