llvm · SamTebbs33 · Sep 4, 2025
diff --git a/llvm/lib/Transforms/Vectorize/VPlan.h b/llvm/lib/Transforms/Vectorize/VPlan.h
@@ -29,6 +29,7 @@
 #include "llvm/ADT/DenseMap.h"
 #include "llvm/ADT/SmallBitVector.h"
 #include "llvm/ADT/SmallPtrSet.h"
+#include "llvm/ADT/SmallSet.h"
 #include "llvm/ADT/SmallVector.h"
 #include "llvm/ADT/Twine.h"
 #include "llvm/ADT/ilist.h"
@@ -3003,8 +3004,11 @@ class VPExpressionRecipe : public VPSingleDefRecipe {
                            {Ext0, Ext1, Mul, Red}) {}
 
   ~VPExpressionRecipe() override {
-    for (auto *R : reverse(ExpressionRecipes))
-      delete R;
+    SmallSet<VPSingleDefRecipe *, 4> ExpressionRecipesSeen;
+    for (auto *R : reverse(ExpressionRecipes)) {
+      if (ExpressionRecipesSeen.insert(R).second)
+        delete R;
+    }
     for (VPValue *T : LiveInPlaceholders)
       delete T;
   }

diff --git a/llvm/lib/Transforms/Vectorize/VPlanRecipes.cpp b/llvm/lib/Transforms/Vectorize/VPlanRecipes.cpp
@@ -2740,9 +2740,8 @@ VPExpressionRecipe::VPExpressionRecipe(
     ExpressionTypes ExpressionType,
     ArrayRef<VPSingleDefRecipe *> ExpressionRecipes)
     : VPSingleDefRecipe(VPDef::VPExpressionSC, {}, {}),
-      ExpressionRecipes(SetVector<VPSingleDefRecipe *>(
-                            ExpressionRecipes.begin(), ExpressionRecipes.end())
-                            .takeVector()),
+      ExpressionRecipes(SmallVector<VPSingleDefRecipe *>(
+          ExpressionRecipes.begin(), ExpressionRecipes.end())),
       ExpressionType(ExpressionType) {
   assert(!ExpressionRecipes.empty() && "Nothing to combine?");
   assert(
@@ -2776,25 +2775,43 @@ VPExpressionRecipe::VPExpressionRecipe(
       R->removeFromParent();
   }
 
+  // Keep track of how many instances of each recipe occur in the recipe list
+  SmallMapVector<VPSingleDefRecipe *, unsigned, 4> ExpressionRecipeCounts;
+  for (auto *R : ExpressionRecipes) {
+    auto *F = ExpressionRecipeCounts.find(R);
+    if (F == ExpressionRecipeCounts.end())
+      ExpressionRecipeCounts.insert(std::make_pair(R, 1));
+    else
+      F->second++;
+  }
+
   // Internalize all external operands to the expression recipes. To do so,
   // create new temporary VPValues for all operands defined by a recipe outside
   // the expression. The original operands are added as operands of the
   // VPExpressionRecipe itself.
   for (auto *R : ExpressionRecipes) {
+    auto *F = ExpressionRecipeCounts.find(R);
+    F->second--;
     for (const auto &[Idx, Op] : enumerate(R->operands())) {
       auto *Def = Op->getDefiningRecipe();
       if (Def && ExpressionRecipesAsSetOfUsers.contains(Def))
         continue;
       addOperand(Op);
-      LiveInPlaceholders.push_back(new VPValue());
-      R->setOperand(Idx, LiveInPlaceholders.back());
+      auto *Tmp = new VPValue();
+      Tmp->setUnderlyingValue(Op->getUnderlyingValue());
+      LiveInPlaceholders.push_back(Tmp);
+      // Only modify this recipe's operands if it's the last time it occurs in
+      // the recipe list
+      if (F->second == 0)
+        R->setOperand(Idx, Tmp);
     }
   }
 }
 
 void VPExpressionRecipe::decompose() {
   for (auto *R : ExpressionRecipes)
-    R->insertBefore(this);
+    if (!R->getParent())
+      R->insertBefore(this);
 
   for (const auto &[Idx, Op] : enumerate(operands()))
     LiveInPlaceholders[Idx]->replaceAllUsesWith(Op);

diff --git a/llvm/test/Transforms/LoopVectorize/vplan-printing-reductions.ll b/llvm/test/Transforms/LoopVectorize/vplan-printing-reductions.ll
@@ -651,3 +651,50 @@ exit:
   %r.0.lcssa = phi i64 [ %rdx.next, %loop ]
   ret i64 %r.0.lcssa
 }
+
+define i64 @print_mulacc_duplicate_extends(ptr nocapture readonly %x, ptr nocapture readonly %y, i32 %n) {
+; CHECK-LABEL: 'print_mulacc_duplicate_extends'
+; CHECK:      VPlan 'Initial VPlan for VF={4},UF>=1' {
+; CHECK-NEXT: Live-in vp<[[VF:%.+]]> = VF
+; CHECK-NEXT: Live-in vp<[[VFxUF:%.+]]> = VF * UF
+; CHECK-NEXT: Live-in vp<[[VTC:%.+]]> = vector-trip-count
+; CHECK-NEXT: Live-in ir<%n> = original trip-count
+; CHECK-EMPTY:
+; CHECK:      vector.ph:
+; CHECK-NEXT:   EMIT vp<[[RDX_START:%.+]]> = reduction-start-vector ir<0>, ir<0>, ir<1>
+; CHECK-NEXT: Successor(s): vector loop
+; CHECK-EMPTY:
+; CHECK-NEXT: <x1> vector loop: {
+; CHECK-NEXT:   vector.body:
+; CHECK-NEXT:     EMIT vp<[[IV:%.+]]> = CANONICAL-INDUCTION ir<0>, vp<[[IV_NEXT:%.+]]>
+; CHECK-NEXT:     WIDEN-REDUCTION-PHI ir<[[RDX:%.+]]> = phi vp<[[RDX_START]]>, vp<[[RDX_NEXT:%.+]]>
+; CHECK-NEXT:     vp<[[STEPS:%.+]]> = SCALAR-STEPS vp<[[IV]]>, ir<1>
+; CHECK-NEXT:     CLONE ir<[[ARRAYIDX0:%.+]]> = getelementptr inbounds ir<%x>, vp<[[STEPS]]>
+; CHECK-NEXT:     vp<[[ADDR0:%.+]]> = vector-pointer ir<[[ARRAYIDX0]]>
+; CHECK-NEXT:     WIDEN ir<[[LOAD0:%.+]]> = load vp<[[ADDR0]]>
+; CHECK-NEXT:     EXPRESSION vp<[[RDX_NEXT:%.+]]> = ir<[[RDX]]> + reduce.sub (mul nsw (ir<[[LOAD0]]> sext to i64), (ir<[[LOAD0]]> sext to i64))
+; CHECK-NEXT:     EMIT vp<[[IV_NEXT]]> = add nuw vp<[[IV]]>, vp<[[VFxUF]]>
+; CHECK-NEXT:     EMIT branch-on-count vp<[[IV_NEXT]]>, vp<[[VTC]]>
+; CHECK-NEXT:   No successors
+; CHECK-NEXT: }
+;
+entry:
+  br label %loop
+
+loop:
+  %iv = phi i32 [ %iv.next, %loop ], [ 0, %entry ]
+  %rdx = phi i64 [ %rdx.next, %loop ], [ 0, %entry ]
+  %arrayidx = getelementptr inbounds i16, ptr %x, i32 %iv
+  %load0 = load i16, ptr %arrayidx, align 4
+  %conv0 = sext i16 %load0 to i32
+  %mul = mul nsw i32 %conv0, %conv0
+  %conv = sext i32 %mul to i64
+  %rdx.next = sub nsw i64 %rdx, %conv
+  %iv.next = add nuw nsw i32 %iv, 1
+  %exitcond = icmp eq i32 %iv.next, %n
+  br i1 %exitcond, label %exit, label %loop
+
+exit:
+  %r.0.lcssa = phi i64 [ %rdx.next, %loop ]
+  ret i64 %r.0.lcssa
+}