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

[Florian Hahn via llvm-commits]

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@@ -1010,16 +994,45 @@ 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);
-  for (VPBasicBlock *VPBB : VPBlockUtils::blocksOnly<VPBasicBlock>(RPOT)) {
-    for (VPRecipeBase &R : make_early_inc_range(*VPBB)) {
-      simplifyRecipe(R, TypeInfo);
+  SetVector<VPRecipeBase *> Worklist;
+  for (VPBasicBlock *VPBB : VPBlockUtils::blocksOnly<VPBasicBlock>(RPOT))
+    for (VPRecipeBase &R : reverse(*VPBB))
+      Worklist.insert(&R);
+
+  while (!Worklist.empty()) {
+    VPRecipeBase *R = Worklist.pop_back_val();
+    if (VPValue *Result = simplifyRecipe(*R, TypeInfo)) {
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fhahn wrote:

Might be worth Turing the check into early continue, to reduce nesting level

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