[PATCH] D93975: [VPlan] Keep start value of VPWidenPHIRecipe as VPValue.

[Florian Hahn via Phabricator via llvm-commits]

fhahn updated this revision to Diff 314883.
fhahn added a comment.

In D93975#2480166 <https://reviews.llvm.org/D93975#2480166>, @gilr wrote:

> I wonder if the code from fixReductions() could be moved (almost as-is) to widenPHIInstruction() as a first step?

Thanks for the suggestion, I put up D94175 <https://reviews.llvm.org/D94175> to move the code and keep RdxDesc in the recipe as a first step. The current patch is much simpler now.


Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D93975/new/

https://reviews.llvm.org/D93975

Files:
  llvm/lib/Transforms/Vectorize/LoopVectorize.cpp
  llvm/lib/Transforms/Vectorize/VPlan.h


Index: llvm/lib/Transforms/Vectorize/VPlan.h
===================================================================
--- llvm/lib/Transforms/Vectorize/VPlan.h
+++ llvm/lib/Transforms/Vectorize/VPlan.h
@@ -948,8 +948,9 @@
 };
 
 /// A recipe for handling all phi nodes except for integer and FP inductions.
-/// For reduction PHIs, RdxDesc needs to be non-null
-class VPWidenPHIRecipe : public VPRecipeBase {
+/// For reduction PHIs, RdxDesc needs to be non-null and the start value is the
+/// first operand of the recipe.
+class VPWidenPHIRecipe : public VPRecipeBase, public VPUser {
   PHINode *Phi;
 
   /// Descriptor for a reduction PHI.
@@ -958,9 +959,10 @@
 public:
   /// Create a new VPWidenPHIRecipe for the reduction \p Phi described by \p
   /// RdxDesc.
-  VPWidenPHIRecipe(PHINode *Phi, RecurrenceDescriptor &RdxDesc)
+  VPWidenPHIRecipe(PHINode *Phi, RecurrenceDescriptor &RdxDesc, VPValue &Start)
       : VPWidenPHIRecipe(Phi) {
     this->RdxDesc = &RdxDesc;
+    addOperand(&Start);
   }
 
   /// Create a VPWidenPHIRecipe for \p Phi
@@ -980,6 +982,11 @@
   /// Print the recipe.
   void print(raw_ostream &O, const Twine &Indent,
              VPSlotTracker &SlotTracker) const override;
+
+  /// Returns the start value of the phi, if it is a reduction.
+  VPValue *getStartValue() {
+    return getNumOperands() == 0 ? nullptr : getOperand(0);
+  }
 };
 
 /// A recipe for vectorizing a phi-node as a sequence of mask-based select
Index: llvm/lib/Transforms/Vectorize/LoopVectorize.cpp
===================================================================
--- llvm/lib/Transforms/Vectorize/LoopVectorize.cpp
+++ llvm/lib/Transforms/Vectorize/LoopVectorize.cpp
@@ -8313,7 +8313,9 @@
 
     if (Legal->isReductionVariable(Phi)) {
       RecurrenceDescriptor &RdxDesc = Legal->getReductionVars()[Phi];
-      return new VPWidenPHIRecipe(Phi, RdxDesc);
+      VPValue *StartV =
+          Plan->getOrAddVPValue(RdxDesc.getRecurrenceStartValue());
+      return new VPWidenPHIRecipe(Phi, RdxDesc, *StartV);
     }
 
     return new VPWidenPHIRecipe(Phi);
@@ -8720,9 +8722,8 @@
 }
 
 void VPWidenPHIRecipe::execute(VPTransformState &State) {
-  Value *StartV = nullptr;
-  if (RdxDesc)
-    StartV = RdxDesc->getRecurrenceStartValue();
+  Value *StartV =
+      getStartValue() ? getStartValue()->getLiveInIRValue() : nullptr;
   State.ILV->widenPHIInstruction(Phi, RdxDesc, StartV, State.UF, State.VF);
 }
 


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