[llvm] [VPlan] Introduce VPlanConstantFolder (PR #125365)

[Luke Lau via llvm-commits]

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@@ -931,9 +932,21 @@ static void recursivelyDeleteDeadRecipes(VPValue *V) {
 }
 
 /// Try to simplify recipe \p R.
-static void simplifyRecipe(VPRecipeBase &R, VPTypeAnalysis &TypeInfo) {
+static void simplifyRecipe(VPRecipeBase &R, VPTypeAnalysis &TypeInfo,
+                           const DataLayout &DL) {
   using namespace llvm::VPlanPatternMatch;
 
+  // Constant folding.
+  VPConstantFolder Folder(DL, TypeInfo);
+  TypeSwitch<VPRecipeBase *, void>(&R)
+      .Case<VPInstruction, VPWidenRecipe, VPWidenCastRecipe, VPReplicateRecipe>(
+          [&](auto *I) {
+            VPlan *Plan = R.getParent()->getPlan();
+            ArrayRef<VPValue *> Ops(I->op_begin(), I->op_end());
+            if (Value *V = Folder.tryToConstantFold(R, I->getOpcode(), Ops))
+              R.getVPSingleValue()->replaceAllUsesWith(Plan->getOrAddLiveIn(V));
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lukel97 wrote:

We should probably return from simplifyRecipe here if R is now dead?

https://github.com/llvm/llvm-project/pull/125365