[llvm] f2e62cf - [VPlan] Add VPPhi subclass for VPInstruction with PHI opcodes.(NFC) (#139151)

[via llvm-commits]

Author: Florian Hahn
Date: 2025-05-10T11:08:00+01:00
New Revision: f2e62cfca5e5719f2d79e4a7ab88fdc239b60bd3

URL: https://github.com/llvm/llvm-project/commit/f2e62cfca5e5719f2d79e4a7ab88fdc239b60bd3
DIFF: https://github.com/llvm/llvm-project/commit/f2e62cfca5e5719f2d79e4a7ab88fdc239b60bd3.diff

LOG: [VPlan] Add VPPhi subclass for VPInstruction with PHI opcodes.(NFC) (#139151)

Similarly to VPInstructionWithType and VPIRPhi, add VPPhi as a subclass
for VPInstruction. This allows implementing the VPPhiAccessors trait,
making available helpers for generic printing of incoming values /
blocks and accessors for incoming blocks and values.

It will also allow properly verifying def-uses for values used by
VPInstructions with PHI opcodes via
https://github.com/llvm/llvm-project/pull/124838.

PR: https://github.com/llvm/llvm-project/pull/139151

Added: 
    

Modified: 
    llvm/lib/Transforms/Vectorize/LoopVectorizationPlanner.h
    llvm/lib/Transforms/Vectorize/VPlan.h
    llvm/lib/Transforms/Vectorize/VPlanRecipes.cpp

Removed: 
    


################################################################################
diff  --git a/llvm/lib/Transforms/Vectorize/LoopVectorizationPlanner.h b/llvm/lib/Transforms/Vectorize/LoopVectorizationPlanner.h
index 98140f6fddc01..bae53c600c18c 100644
--- a/llvm/lib/Transforms/Vectorize/LoopVectorizationPlanner.h
+++ b/llvm/lib/Transforms/Vectorize/LoopVectorizationPlanner.h
@@ -252,8 +252,7 @@ class VPBuilder {
 
   VPInstruction *createScalarPhi(ArrayRef<VPValue *> IncomingValues,
                                  DebugLoc DL, const Twine &Name = "") {
-    return tryInsertInstruction(
-        new VPInstruction(Instruction::PHI, IncomingValues, DL, Name));
+    return tryInsertInstruction(new VPPhi(IncomingValues, DL, Name));
   }
 
   /// Convert the input value \p Current to the corresponding value of an

diff  --git a/llvm/lib/Transforms/Vectorize/VPlan.h b/llvm/lib/Transforms/Vectorize/VPlan.h
index 136ee36636565..2a726e058166d 100644
--- a/llvm/lib/Transforms/Vectorize/VPlan.h
+++ b/llvm/lib/Transforms/Vectorize/VPlan.h
@@ -1143,6 +1143,21 @@ class VPPhiAccessors {
 #endif
 };
 
+struct VPPhi : public VPInstruction, public VPPhiAccessors {
+  VPPhi(ArrayRef<VPValue *> Operands, DebugLoc DL, const Twine &Name = "")
+      : VPInstruction(Instruction::PHI, Operands, DL, Name) {}
+
+  static inline bool classof(const VPRecipeBase *U) {
+    auto *R = dyn_cast<VPInstruction>(U);
+    return R && R->getOpcode() == Instruction::PHI;
+  }
+
+  void execute(VPTransformState &State) override;
+
+protected:
+  const VPRecipeBase *getAsRecipe() const override { return this; }
+};
+
 /// A recipe to wrap on original IR instruction not to be modified during
 /// execution, except for PHIs. PHIs are modeled via the VPIRPhi subclass.
 /// Expect PHIs, VPIRInstructions cannot have any operands.

diff  --git a/llvm/lib/Transforms/Vectorize/VPlanRecipes.cpp b/llvm/lib/Transforms/Vectorize/VPlanRecipes.cpp
index 056a9aa0565d3..b2b2faafb6c26 100644
--- a/llvm/lib/Transforms/Vectorize/VPlanRecipes.cpp
+++ b/llvm/lib/Transforms/Vectorize/VPlanRecipes.cpp
@@ -492,16 +492,7 @@ Value *VPInstruction::generate(VPTransformState &State) {
     return Builder.CreateCmp(getPredicate(), A, B, Name);
   }
   case Instruction::PHI: {
-    assert(getParent() ==
-               getParent()->getPlan()->getVectorLoopRegion()->getEntry() &&
-           "VPInstructions with PHI opcodes must be used for header phis only "
-           "at the moment");
-    BasicBlock *VectorPH =
-        State.CFG.VPBB2IRBB.at(getParent()->getCFGPredecessor(0));
-    Value *Start = State.get(getOperand(0), VPLane(0));
-    PHINode *Phi = State.Builder.CreatePHI(Start->getType(), 2, Name);
-    Phi->addIncoming(Start, VectorPH);
-    return Phi;
+    llvm_unreachable("should be handled by VPPhi::execute");
   }
   case Instruction::Select: {
     bool OnlyFirstLaneUsed = vputils::onlyFirstLaneUsed(this);
@@ -1131,6 +1122,19 @@ void VPInstructionWithType::print(raw_ostream &O, const Twine &Indent,
 }
 #endif
 
+void VPPhi::execute(VPTransformState &State) {
+  State.setDebugLocFrom(getDebugLoc());
+  assert(getParent() ==
+             getParent()->getPlan()->getVectorLoopRegion()->getEntry() &&
+         "VPInstructions with PHI opcodes must be used for header phis only "
+         "at the moment");
+  BasicBlock *VectorPH = State.CFG.VPBB2IRBB.at(getIncomingBlock(0));
+  Value *Start = State.get(getIncomingValue(0), VPLane(0));
+  PHINode *Phi = State.Builder.CreatePHI(Start->getType(), 2, getName());
+  Phi->addIncoming(Start, VectorPH);
+  State.set(this, Phi, VPLane(0));
+}
+
 VPIRInstruction *VPIRInstruction ::create(Instruction &I) {
   if (auto *Phi = dyn_cast<PHINode>(&I))
     return new VPIRPhi(*Phi);