[llvm-branch-commits] [llvm] [LoopVectorize] Support vectorization of compressing patterns (PR #214491)

[Benjamin Maxwell via llvm-branch-commits]

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@@ -2903,6 +2920,38 @@ void LoopVectorizationCostModel::collectLoopUniforms(ElementCount VF) {
     AddToWorklistIfAllowed(IndUpdate);
   }
 
+  // Handle monotonic phis (similarly to induction vars).
+  for (const auto &MonotonicPHI : Legal->getMonotonicPHIs()) {
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MacDue wrote:

I'll have a look into reworking the descriptor to only allow compresstore/expandload uses for now. I agree it would be safer (and less of a hack than the invalid cost). 

https://github.com/llvm/llvm-project/pull/214491