llvm-project

7c5c58cd - [X86] getFauxShuffleMask - OR(SHUF(),SHUF()) - treat undemanded elements as undef (#182678)

[X86] getFauxShuffleMask - OR(SHUF(),SHUF()) - treat undemanded elements as undef (#182678) We have to be careful when attempting to decode OR() patterns as shuffles - we can't forward demanded undef elements in both sources as an undef result as it can lead to infinite loops during widening (#49393). But if we don't demand the element in the first place (based off demanded elts masks during recursive shuffle combines), then it doesn't matter what the elements contain and we can treat it as a SM_SentinelUndef shuffle element. Noticed while working on #137422