[LV] Keep duplicate recipes in VPExpressionRecipe

The VPExpressionRecipe class uses a set to store its bundled recipes. If
repeated recipes are bundled then the duplicates will be lost, causing
the following recipes to not be at the expected place in the set.

When printing a reduce.add(mul(ext, ext)) bundle, if the extends are the
same then the 3rd element of the set will the the reduction, rather than
the expected mul, causing a cast error. With this change, the recipes
are at the expected index in the set.

Fixes #156464

Author: SamTebbs33

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"
@@ -3039,8 +3040,11 @@ class VPExpressionRecipe : public VPSingleDefRecipe {
   }
 
   ~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;
   }

llvm/lib/Transforms/Vectorize/VPlanRecipes.cpp

@@ -2755,9 +2755,8 @@ 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(
@@ -2791,25 +2790,43 @@ 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);

llvm/test/Transforms/LoopVectorize/vplan-printing-reductions.ll

@@ -753,3 +753,50 @@ 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
+}