[llvm] [VPlan] Process simplifyRecipes via a worklist (PR #133977)

[Ramkumar Ramachandra via llvm-commits]

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@@ -1075,16 +1003,110 @@ static void simplifyRecipe(VPRecipeBase &R, VPTypeAnalysis &TypeInfo) {
              m_DerivedIV(m_SpecificInt(0), m_SpecificInt(0), m_VPValue()))) &&
       TypeInfo.inferScalarType(R.getOperand(1)) ==
           TypeInfo.inferScalarType(R.getVPSingleValue()))
-    return R.getVPSingleValue()->replaceAllUsesWith(R.getOperand(1));
+    return R.getOperand(1);
+
+  return nullptr;
 }
 
 void VPlanTransforms::simplifyRecipes(VPlan &Plan, Type &CanonicalIVTy) {
   ReversePostOrderTraversal<VPBlockDeepTraversalWrapper<VPBlockBase *>> RPOT(
       Plan.getEntry());
   VPTypeAnalysis TypeInfo(&CanonicalIVTy);
+  SetVector<VPRecipeBase *> Worklist;
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artagnon wrote:

It doesn't matter yet, but matters when you will put up a patch with functional changes: I believe the order of simplification matters unlike in InstCombine, but I'm happy to address the point in the follow-up patch. Let's keep this thread open in case other reviewers have something to say about this.

https://github.com/llvm/llvm-project/pull/133977