[VPlan] Truncate/Extend ComputeReductionResult at construction (NFC). #141860

fhahn · 2025-05-28T21:26:58Z

Instead of looking up the narrower reduction type via getRecurrenceType we can generate the needed extend directly at constructiond re-use the truncated value from the loop.

llvmbot · 2025-05-28T21:27:34Z

@llvm/pr-subscribers-vectorizers

@llvm/pr-subscribers-llvm-transforms

Author: Florian Hahn (fhahn)

Changes

Instead of looking up the narrower reduction type via getRecurrenceType we can generate the needed extend directly at constructiond re-use the truncated value from the loop.

Full diff: https://github.com/llvm/llvm-project/pull/141860.diff

6 Files Affected:

(modified) llvm/lib/Transforms/Vectorize/LoopVectorize.cpp (+33-23)
(modified) llvm/lib/Transforms/Vectorize/VPlanRecipes.cpp (+4-19)
(modified) llvm/test/Transforms/LoopVectorize/X86/cost-model.ll (+1-2)
(modified) llvm/test/Transforms/LoopVectorize/epilog-vectorization-reductions.ll (+2-4)
(modified) llvm/test/Transforms/LoopVectorize/reduction-small-size.ll (+3-6)
(modified) llvm/test/Transforms/LoopVectorize/scalable-reduction-inloop.ll (+1-3)

diff --git a/llvm/lib/Transforms/Vectorize/LoopVectorize.cpp b/llvm/lib/Transforms/Vectorize/LoopVectorize.cpp
index 8040d375f0dbd..4f236869726fb 100644
--- a/llvm/lib/Transforms/Vectorize/LoopVectorize.cpp
+++ b/llvm/lib/Transforms/Vectorize/LoopVectorize.cpp
@@ -7595,6 +7595,13 @@ static void fixReductionScalarResumeWhenVectorizingEpilog(
     auto *VPI = dyn_cast<VPInstruction>(U);
     return VPI && VPI->getOpcode() == VPInstruction::ResumePhi;
   };
+  if (EpiRedResult->getNumUsers() == 1 &&
+      isa<VPInstructionWithType>(*EpiRedResult->user_begin())) {
+    assert((EpiRedResult->getOpcode() == Instruction::SExt ||
+            EpiRedResult->getOpcode() == Instruction::ZExt) &&
+           "can only have SExt/ZExt users");
+    EpiRedResult = cast<VPInstructionWithType>(*EpiRedResult->user_begin());
+  }
   assert(count_if(EpiRedResult->users(), IsResumePhi) == 1 &&
          "ResumePhi must have a single user");
   auto *EpiResumePhiVPI =
@@ -9530,29 +9537,6 @@ void LoopVectorizationPlanner::adjustRecipesForReductions(
         PhiR->setOperand(1, NewExitingVPV);
     }
 
-    // If the vector reduction can be performed in a smaller type, we truncate
-    // then extend the loop exit value to enable InstCombine to evaluate the
-    // entire expression in the smaller type.
-    Type *PhiTy = PhiR->getStartValue()->getLiveInIRValue()->getType();
-    if (MinVF.isVector() && PhiTy != RdxDesc.getRecurrenceType() &&
-        !RecurrenceDescriptor::isAnyOfRecurrenceKind(
-            RdxDesc.getRecurrenceKind())) {
-      assert(!PhiR->isInLoop() && "Unexpected truncated inloop reduction!");
-      Type *RdxTy = RdxDesc.getRecurrenceType();
-      auto *Trunc =
-          new VPWidenCastRecipe(Instruction::Trunc, NewExitingVPV, RdxTy);
-      auto *Extnd =
-          RdxDesc.isSigned()
-              ? new VPWidenCastRecipe(Instruction::SExt, Trunc, PhiTy)
-              : new VPWidenCastRecipe(Instruction::ZExt, Trunc, PhiTy);
-
-      Trunc->insertAfter(NewExitingVPV->getDefiningRecipe());
-      Extnd->insertAfter(Trunc);
-      if (PhiR->getOperand(1) == NewExitingVPV)
-        PhiR->setOperand(1, Extnd->getVPSingleValue());
-      NewExitingVPV = Extnd;
-    }
-
     // We want code in the middle block to appear to execute on the location of
     // the scalar loop's latch terminator because: (a) it is all compiler
     // generated, (b) these instructions are always executed after evaluating
@@ -9584,6 +9568,32 @@ void LoopVectorizationPlanner::adjustRecipesForReductions(
           Builder.createNaryOp(VPInstruction::ComputeReductionResult,
                                {PhiR, NewExitingVPV}, Flags, ExitDL);
     }
+    // If the vector reduction can be performed in a smaller type, we truncate
+    // then extend the loop exit value to enable InstCombine to evaluate the
+    // entire expression in the smaller type.
+    Type *PhiTy = PhiR->getStartValue()->getLiveInIRValue()->getType();
+    if (MinVF.isVector() && PhiTy != RdxDesc.getRecurrenceType() &&
+        !RecurrenceDescriptor::isAnyOfRecurrenceKind(
+            RdxDesc.getRecurrenceKind())) {
+      assert(!PhiR->isInLoop() && "Unexpected truncated inloop reduction!");
+      Type *RdxTy = RdxDesc.getRecurrenceType();
+      auto *Trunc =
+          new VPWidenCastRecipe(Instruction::Trunc, NewExitingVPV, RdxTy);
+      Instruction::CastOps ExtendOpc =
+          RdxDesc.isSigned() ? Instruction::SExt : Instruction::ZExt;
+      auto *Extnd = new VPWidenCastRecipe(ExtendOpc, Trunc, PhiTy);
+      Trunc->insertAfter(NewExitingVPV->getDefiningRecipe());
+      Extnd->insertAfter(Trunc);
+      if (PhiR->getOperand(1) == NewExitingVPV)
+        PhiR->setOperand(1, Extnd->getVPSingleValue());
+
+      // Update ComputeReductionResult with the truncated exiting value and
+      // extend its result.
+      FinalReductionResult->setOperand(1, Trunc);
+      FinalReductionResult =
+          Builder.createScalarCast(ExtendOpc, FinalReductionResult, PhiTy, {});
+    }
+
     // Update all users outside the vector region.
     OrigExitingVPV->replaceUsesWithIf(
         FinalReductionResult, [FinalReductionResult](VPUser &User, unsigned) {
diff --git a/llvm/lib/Transforms/Vectorize/VPlanRecipes.cpp b/llvm/lib/Transforms/Vectorize/VPlanRecipes.cpp
index 266f658b1f9c1..2659cc6bf8682 100644
--- a/llvm/lib/Transforms/Vectorize/VPlanRecipes.cpp
+++ b/llvm/lib/Transforms/Vectorize/VPlanRecipes.cpp
@@ -633,7 +633,6 @@ Value *VPInstruction::generate(VPTransformState &State) {
     // FIXME: The cross-recipe dependency on VPReductionPHIRecipe is temporary
     // and will be removed by breaking up the recipe further.
     auto *PhiR = cast<VPReductionPHIRecipe>(getOperand(0));
-    auto *OrigPhi = cast<PHINode>(PhiR->getUnderlyingValue());
     // Get its reduction variable descriptor.
     const RecurrenceDescriptor &RdxDesc = PhiR->getRecurrenceDescriptor();
 
@@ -641,7 +640,6 @@ Value *VPInstruction::generate(VPTransformState &State) {
     assert(!RecurrenceDescriptor::isFindLastIVRecurrenceKind(RK) &&
            "should be handled by ComputeFindLastIVResult");
 
-    Type *PhiTy = OrigPhi->getType();
     // The recipe's operands are the reduction phi, followed by one operand for
     // each part of the reduction.
     unsigned UF = getNumOperands() - 1;
@@ -653,15 +651,6 @@ Value *VPInstruction::generate(VPTransformState &State) {
     if (hasFastMathFlags())
       Builder.setFastMathFlags(getFastMathFlags());
 
-    // If the vector reduction can be performed in a smaller type, we truncate
-    // then extend the loop exit value to enable InstCombine to evaluate the
-    // entire expression in the smaller type.
-    // TODO: Handle this in truncateToMinBW.
-    if (State.VF.isVector() && PhiTy != RdxDesc.getRecurrenceType()) {
-      Type *RdxVecTy = VectorType::get(RdxDesc.getRecurrenceType(), State.VF);
-      for (unsigned Part = 0; Part < UF; ++Part)
-        RdxParts[Part] = Builder.CreateTrunc(RdxParts[Part], RdxVecTy);
-    }
     // Reduce all of the unrolled parts into a single vector.
     Value *ReducedPartRdx = RdxParts[0];
     if (PhiR->isOrdered()) {
@@ -687,19 +676,14 @@ Value *VPInstruction::generate(VPTransformState &State) {
       // TODO: Support in-order reductions based on the recurrence descriptor.
       // All ops in the reduction inherit fast-math-flags from the recurrence
       // descriptor.
-      if (RecurrenceDescriptor::isAnyOfRecurrenceKind(RK))
+      if (RecurrenceDescriptor::isAnyOfRecurrenceKind(RK)) {
+        auto *OrigPhi = cast<PHINode>(PhiR->getUnderlyingValue());
         ReducedPartRdx =
             createAnyOfReduction(Builder, ReducedPartRdx,
                                  RdxDesc.getRecurrenceStartValue(), OrigPhi);
-      else
+      } else
         ReducedPartRdx = createSimpleReduction(Builder, ReducedPartRdx, RK);
 
-      // If the reduction can be performed in a smaller type, we need to extend
-      // the reduction to the wider type before we branch to the original loop.
-      if (PhiTy != RdxDesc.getRecurrenceType())
-        ReducedPartRdx = RdxDesc.isSigned()
-                             ? Builder.CreateSExt(ReducedPartRdx, PhiTy)
-                             : Builder.CreateZExt(ReducedPartRdx, PhiTy);
     }
 
     return ReducedPartRdx;
@@ -1051,6 +1035,7 @@ void VPInstruction::print(raw_ostream &O, const Twine &Indent,
 void VPInstructionWithType::execute(VPTransformState &State) {
   State.setDebugLocFrom(getDebugLoc());
   switch (getOpcode()) {
+  case Instruction::SExt:
   case Instruction::ZExt:
   case Instruction::Trunc: {
     Value *Op = State.get(getOperand(0), VPLane(0));
diff --git a/llvm/test/Transforms/LoopVectorize/X86/cost-model.ll b/llvm/test/Transforms/LoopVectorize/X86/cost-model.ll
index 7c42c3d9cd52e..a6ac9c2886a92 100644
--- a/llvm/test/Transforms/LoopVectorize/X86/cost-model.ll
+++ b/llvm/test/Transforms/LoopVectorize/X86/cost-model.ll
@@ -1167,8 +1167,7 @@ define i32 @narrowed_reduction(ptr %a, i1 %cmp) #0 {
 ; CHECK-NEXT:    [[INDEX_NEXT]] = add nuw i32 [[INDEX]], 16
 ; CHECK-NEXT:    br i1 true, label [[MIDDLE_BLOCK:%.*]], label [[VECTOR_BODY]], !llvm.loop [[LOOP28:![0-9]+]]
 ; CHECK:       middle.block:
-; CHECK-NEXT:    [[TMP10:%.*]] = trunc <16 x i32> [[TMP7]] to <16 x i1>
-; CHECK-NEXT:    [[TMP20:%.*]] = call i1 @llvm.vector.reduce.or.v16i1(<16 x i1> [[TMP10]])
+; CHECK-NEXT:    [[TMP20:%.*]] = call i1 @llvm.vector.reduce.or.v16i1(<16 x i1> [[TMP5]])
 ; CHECK-NEXT:    [[TMP21:%.*]] = zext i1 [[TMP20]] to i32
 ; CHECK-NEXT:    br i1 true, label [[EXIT:%.*]], label [[VEC_EPILOG_PH]]
 ; CHECK:       scalar.ph:
diff --git a/llvm/test/Transforms/LoopVectorize/epilog-vectorization-reductions.ll b/llvm/test/Transforms/LoopVectorize/epilog-vectorization-reductions.ll
index 0a2bb8d5682f2..c101d6a19aa2e 100644
--- a/llvm/test/Transforms/LoopVectorize/epilog-vectorization-reductions.ll
+++ b/llvm/test/Transforms/LoopVectorize/epilog-vectorization-reductions.ll
@@ -208,8 +208,7 @@ define i16 @reduction_or_trunc(ptr noalias nocapture %ptr) {
 ; CHECK-NEXT:    [[TMP8:%.*]] = icmp eq i32 [[INDEX_NEXT]], 256
 ; CHECK-NEXT:    br i1 [[TMP8]], label [[MIDDLE_BLOCK:%.*]], label [[VECTOR_BODY]], !llvm.loop [[LOOP8:![0-9]+]]
 ; CHECK:       middle.block:
-; CHECK-NEXT:    [[TMP9:%.*]] = trunc <4 x i32> [[TMP7]] to <4 x i16>
-; CHECK-NEXT:    [[TMP10:%.*]] = call i16 @llvm.vector.reduce.or.v4i16(<4 x i16> [[TMP9]])
+; CHECK-NEXT:    [[TMP10:%.*]] = call i16 @llvm.vector.reduce.or.v4i16(<4 x i16> [[TMP6]])
 ; CHECK-NEXT:    [[TMP11:%.*]] = zext i16 [[TMP10]] to i32
 ; CHECK-NEXT:    br i1 true, label [[FOR_END:%.*]], label [[VEC_EPILOG_ITER_CHECK:%.*]]
 ; CHECK:       vec.epilog.iter.check:
@@ -234,8 +233,7 @@ define i16 @reduction_or_trunc(ptr noalias nocapture %ptr) {
 ; CHECK-NEXT:    [[TMP21:%.*]] = icmp eq i32 [[INDEX_NEXT4]], 256
 ; CHECK-NEXT:    br i1 [[TMP21]], label [[VEC_EPILOG_MIDDLE_BLOCK:%.*]], label [[VEC_EPILOG_VECTOR_BODY]], !llvm.loop [[LOOP9:![0-9]+]]
 ; CHECK:       vec.epilog.middle.block:
-; CHECK-NEXT:    [[TMP22:%.*]] = trunc <4 x i32> [[TMP20]] to <4 x i16>
-; CHECK-NEXT:    [[TMP23:%.*]] = call i16 @llvm.vector.reduce.or.v4i16(<4 x i16> [[TMP22]])
+; CHECK-NEXT:    [[TMP23:%.*]] = call i16 @llvm.vector.reduce.or.v4i16(<4 x i16> [[TMP19]])
 ; CHECK-NEXT:    [[TMP24:%.*]] = zext i16 [[TMP23]] to i32
 ; CHECK-NEXT:    br i1 true, label [[FOR_END]], label [[VEC_EPILOG_SCALAR_PH]]
 ; CHECK:       vec.epilog.scalar.ph:
diff --git a/llvm/test/Transforms/LoopVectorize/reduction-small-size.ll b/llvm/test/Transforms/LoopVectorize/reduction-small-size.ll
index 796c1d116aa19..13cc1b657d231 100644
--- a/llvm/test/Transforms/LoopVectorize/reduction-small-size.ll
+++ b/llvm/test/Transforms/LoopVectorize/reduction-small-size.ll
@@ -25,8 +25,7 @@ define i8 @PR34687(i1 %c, i32 %x, i32 %n) {
 ; CHECK-NEXT:    [[TMP5:%.*]] = icmp eq i32 [[INDEX_NEXT]], [[N_VEC]]
 ; CHECK-NEXT:    br i1 [[TMP5]], label [[MIDDLE_BLOCK:%.*]], label [[VECTOR_BODY]], !llvm.loop [[LOOP0:![0-9]+]]
 ; CHECK:       middle.block:
-; CHECK-NEXT:    [[TMP6:%.*]] = trunc <4 x i32> [[TMP4]] to <4 x i8>
-; CHECK-NEXT:    [[TMP7:%.*]] = call i8 @llvm.vector.reduce.add.v4i8(<4 x i8> [[TMP6]])
+; CHECK-NEXT:    [[TMP7:%.*]] = call i8 @llvm.vector.reduce.add.v4i8(<4 x i8> [[TMP3]])
 ; CHECK-NEXT:    [[TMP8:%.*]] = zext i8 [[TMP7]] to i32
 ; CHECK-NEXT:    [[CMP_N:%.*]] = icmp eq i32 [[N]], [[N_VEC]]
 ; CHECK-NEXT:    br i1 [[CMP_N]], label [[FOR_END:%.*]], label [[SCALAR_PH]]
@@ -104,8 +103,7 @@ define i8 @PR34687_no_undef(i1 %c, i32 %x, i32 %n) {
 ; CHECK-NEXT:    [[TMP7:%.*]] = icmp eq i32 [[INDEX_NEXT]], [[N_VEC]]
 ; CHECK-NEXT:    br i1 [[TMP7]], label [[MIDDLE_BLOCK:%.*]], label [[VECTOR_BODY]], !llvm.loop [[LOOP4:![0-9]+]]
 ; CHECK:       middle.block:
-; CHECK-NEXT:    [[TMP8:%.*]] = trunc <4 x i32> [[TMP6]] to <4 x i8>
-; CHECK-NEXT:    [[TMP9:%.*]] = call i8 @llvm.vector.reduce.add.v4i8(<4 x i8> [[TMP8]])
+; CHECK-NEXT:    [[TMP9:%.*]] = call i8 @llvm.vector.reduce.add.v4i8(<4 x i8> [[TMP5]])
 ; CHECK-NEXT:    [[TMP10:%.*]] = zext i8 [[TMP9]] to i32
 ; CHECK-NEXT:    [[CMP_N:%.*]] = icmp eq i32 [[N]], [[N_VEC]]
 ; CHECK-NEXT:    br i1 [[CMP_N]], label [[FOR_END:%.*]], label [[SCALAR_PH]]
@@ -183,8 +181,7 @@ define i32 @PR35734(i32 %x, i32 %y) {
 ; CHECK-NEXT:    [[TMP7:%.*]] = icmp eq i32 [[INDEX_NEXT]], [[N_VEC]]
 ; CHECK-NEXT:    br i1 [[TMP7]], label [[MIDDLE_BLOCK:%.*]], label [[VECTOR_BODY]], !llvm.loop [[LOOP6:![0-9]+]]
 ; CHECK:       middle.block:
-; CHECK-NEXT:    [[TMP8:%.*]] = trunc <4 x i32> [[TMP6]] to <4 x i1>
-; CHECK-NEXT:    [[TMP9:%.*]] = call i1 @llvm.vector.reduce.add.v4i1(<4 x i1> [[TMP8]])
+; CHECK-NEXT:    [[TMP9:%.*]] = call i1 @llvm.vector.reduce.add.v4i1(<4 x i1> [[TMP5]])
 ; CHECK-NEXT:    [[TMP10:%.*]] = sext i1 [[TMP9]] to i32
 ; CHECK-NEXT:    [[CMP_N:%.*]] = icmp eq i32 [[TMP1]], [[N_VEC]]
 ; CHECK-NEXT:    br i1 [[CMP_N]], label [[FOR_END:%.*]], label [[SCALAR_PH]]
diff --git a/llvm/test/Transforms/LoopVectorize/scalable-reduction-inloop.ll b/llvm/test/Transforms/LoopVectorize/scalable-reduction-inloop.ll
index 223acfa2e3a25..6e251cb7b0ad3 100644
--- a/llvm/test/Transforms/LoopVectorize/scalable-reduction-inloop.ll
+++ b/llvm/test/Transforms/LoopVectorize/scalable-reduction-inloop.ll
@@ -28,9 +28,7 @@ define i8 @reduction_add_trunc(ptr noalias nocapture %A) {
 ; CHECK-NEXT:    [[INDEX_NEXT]] = add nuw i32 [[INDEX]], [[TMP31]]
 ; CHECK-NEXT:    [[TMP32:%.*]] = icmp eq i32 [[INDEX_NEXT]], {{%.*}}
 ; CHECK:       middle.block:
-; CHECK-NEXT:    [[TMP37:%.*]] = trunc <vscale x 8 x i32> [[TMP34]] to <vscale x 8 x i8>
-; CHECK-NEXT:    [[TMP38:%.*]] = trunc <vscale x 8 x i32> [[TMP36]] to <vscale x 8 x i8>
-; CHECK-NEXT:    [[BIN_RDX:%.*]] = add <vscale x 8 x i8> [[TMP38]], [[TMP37]]
+; CHECK-NEXT:    [[BIN_RDX:%.*]] = add <vscale x 8 x i8> [[TMP35]], [[TMP33]]
 ; CHECK-NEXT:    [[TMP39:%.*]] = call i8 @llvm.vector.reduce.add.nxv8i8(<vscale x 8 x i8> [[BIN_RDX]])
 ; CHECK-NEXT:    [[TMP40:%.*]] = zext i8 [[TMP39]] to i32
 ; CHECK-NEXT:    %cmp.n = icmp eq i32 256, %n.vec

github-actions · 2025-05-28T21:30:13Z

✅ With the latest revision this PR passed the C/C++ code formatter.

Replace VPReductionPHIRecipe with RecurKind in VPReductionPHIRecipe, as all VPlan analyses and codegen only require the recurrence kind. This enables creating new VPReductionPHIRecipe directly in LV, without needing to construction a whole RecurrenceDescriptor object. Depends on llvm#141860 llvm#141932 llvm#142290 llvm#142291

david-arm · 2025-06-09T12:47:30Z

llvm/lib/Transforms/Vectorize/LoopVectorize.cpp

+  if (EpiRedResult->getNumUsers() == 1 &&
+      isa<VPInstructionWithType>(*EpiRedResult->user_begin())) {
+    EpiRedResult = cast<VPInstructionWithType>(*EpiRedResult->user_begin());
+    assert((EpiRedResult->getOpcode() == Instruction::SExt ||


Do we already have a m_ZExtOrSExt match function for this somewhere?

Ah yes, we already have that. Used to look through the cast, thanks

david-arm · 2025-06-09T12:50:57Z

llvm/lib/Transforms/Vectorize/LoopVectorize.cpp

@@ -7270,6 +7270,13 @@ static void fixReductionScalarResumeWhenVectorizingEpilog(
  // created a bc.merge.rdx Phi after the main vector body. Ensure that we carry
  // over the incoming values correctly.
  using namespace VPlanPatternMatch;
+  if (EpiRedResult->getNumUsers() == 1 &&
+      isa<VPInstructionWithType>(*EpiRedResult->user_begin())) {
+    EpiRedResult = cast<VPInstructionWithType>(*EpiRedResult->user_begin());


Do you know why we don't just pass in the sext/zext as the R argument to fixReductionScalarResumeWhenVectorizingEpilog and then look through the sext/zext?

It is slightly simpler to pass the resume phi node instead of the ComputeRdxResult VPInstruction, which saves the find. Refactored in 4a6d31f and updated here to look through the SExt/ZExt using match() above

Replace VPReductionPHIRecipe with RecurKind in VPReductionPHIRecipe, as all VPlan analyses and codegen only require the recurrence kind. This enables creating new VPReductionPHIRecipe directly in LV, without needing to construction a whole RecurrenceDescriptor object. Depends on llvm#141860 llvm#141932 llvm#142290 llvm#142291

fixReductionScalarResumeWhenVectorizingEpilog updates the resume phis in the scalar preheader. Instead of looking at all recipes in the middle block and finding their resume-phi users we can iterate over all resume phis in the scalar preheader directly. This slightly simplifies the code and removes the need to look for the resume phi. Also slightly simplifies #141860.

Instead of looking up the narrower reduction type via getRecurrenceType we can generate the needed extend directly at constructiond re-use the truncated value from the loop.

Replace VPReductionPHIRecipe with RecurKind in VPReductionPHIRecipe, as all VPlan analyses and codegen only require the recurrence kind. This enables creating new VPReductionPHIRecipe directly in LV, without needing to construction a whole RecurrenceDescriptor object. Depends on llvm#141860 llvm#141932 llvm#142290 llvm#142291

…izing (NFC). fixReductionScalarResumeWhenVectorizingEpilog updates the resume phis in the scalar preheader. Instead of looking at all recipes in the middle block and finding their resume-phi users we can iterate over all resume phis in the scalar preheader directly. This slightly simplifies the code and removes the need to look for the resume phi. Also slightly simplifies llvm/llvm-project#141860.

fixReductionScalarResumeWhenVectorizingEpilog updates the resume phis in the scalar preheader. Instead of looking at all recipes in the middle block and finding their resume-phi users we can iterate over all resume phis in the scalar preheader directly. This slightly simplifies the code and removes the need to look for the resume phi. Also slightly simplifies llvm#141860.

david-arm · 2025-06-11T14:23:06Z

I think it might be worth rebasing the patch to see if the tests then pass.

fixReductionScalarResumeWhenVectorizingEpilog updates the resume phis in the scalar preheader. Instead of looking at all recipes in the middle block and finding their resume-phi users we can iterate over all resume phis in the scalar preheader directly. This slightly simplifies the code and removes the need to look for the resume phi. Also slightly simplifies llvm#141860.

Replace VPReductionPHIRecipe with RecurKind in VPReductionPHIRecipe, as all VPlan analyses and codegen only require the recurrence kind. This enables creating new VPReductionPHIRecipe directly in LV, without needing to construction a whole RecurrenceDescriptor object. Depends on llvm#141860 llvm#141932 llvm#142290 llvm#142291

fhahn requested review from Mel-Chen, ayalz and aniragil May 28, 2025 21:26

llvmbot added vectorizers llvm:transforms labels May 28, 2025

fhahn force-pushed the vplan-trunc-reduction-result branch 2 times, most recently from 6eb0f45 to c8ff5bb Compare June 1, 2025 21:17

fhahn mentioned this pull request Jun 1, 2025

[VPlan] Replace RdxDesc with RecurKind in VPReductionPHIRecipe (NFC). #142322

Open

fhahn force-pushed the vplan-trunc-reduction-result branch from c8ff5bb to 2299808 Compare June 3, 2025 14:09

fhahn force-pushed the vplan-trunc-reduction-result branch 2 times, most recently from 1c356a4 to ef5fa70 Compare June 8, 2025 12:05

david-arm reviewed Jun 9, 2025

View reviewed changes

fhahn force-pushed the vplan-trunc-reduction-result branch from ef5fa70 to 4f45ba2 Compare June 9, 2025 20:15

[VPlan] Truncate/Extend ComputeReductionResult at construction (NFC).

76eb1d8

Instead of looking up the narrower reduction type via getRecurrenceType we can generate the needed extend directly at constructiond re-use the truncated value from the loop.

fhahn force-pushed the vplan-trunc-reduction-result branch from 4f45ba2 to 76eb1d8 Compare June 9, 2025 21:16

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