[llvm-branch-commits] [llvm] [LoopVectorize] Support vectorization of compressing patterns in VPlan (PR #140723)

[Sergey Kachkov via llvm-branch-commits]

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@@ -8430,6 +8479,46 @@ VPlanPtr LoopVectorizationPlanner::tryToBuildVPlanWithVPRecipes(
   // bring the VPlan to its final state.
   // ---------------------------------------------------------------------------
 
+  // Adjust the recipes for any monotonic phis.
+  for (VPRecipeBase &R : HeaderVPBB->phis()) {
+    auto *MonotonicPhi = dyn_cast<VPMonotonicPHIRecipe>(&R);
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skachkov-sc wrote:

Do you mean VPIRPhi recipe? I think it's possible, but I'm slightly concerned that semantically  VPMonotonicPHIRecipe models loop header phi so it should be derived from VPHeaderPHIRecipe. But yes, we can distinguish monotonic phis using LoopVectorizationLegality

https://github.com/llvm/llvm-project/pull/140723