[llvm] [LV] Expand VPWidenIntOrFpInductionRecipe into separate recipes (PR #118638)

[Luke Lau via llvm-commits]

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@@ -2180,10 +2183,152 @@ class VPWidenIntOrFpInductionRecipe : public VPHeaderPHIRecipe {
   }
 
   /// Returns the VPValue representing the value of this induction at
-  /// the last unrolled part, if it exists. Returns itself if unrolling did not
+  /// the last unrolled part, if it exists. Returns nullptr if unrolling did not
   /// take place.
   VPValue *getLastUnrolledPartOperand() {
-    return getNumOperands() == 5 ? getOperand(4) : this;
+    return getNumOperands() == 5 ? getOperand(4) : nullptr;
+  }
+};
+
+/// A recipe to compute the initial value for a widened IV, expanded from
+/// VPWidenIntOrFpInductionRecipe.
+class VPWidenIntOrFpInductionInitialRecipe : public VPSingleDefRecipe {
+  Instruction *IV;
+  const InductionDescriptor &ID;
+
+public:
+  VPWidenIntOrFpInductionInitialRecipe(Instruction *IV, VPValue *Start,
+                                       VPValue *Step,
+                                       const InductionDescriptor &ID)
+      : VPSingleDefRecipe(VPDef::VPWidenIntOrFpInductionStartSC, {Start, Step}),
+        IV(IV), ID(ID) {
+    assert((isa<PHINode>(IV) || isa<TruncInst>(IV)) &&
+           "Expected either an induction phi-node or a truncate of it!");
+  }
+
+  ~VPWidenIntOrFpInductionInitialRecipe() override = default;
+
+  VPWidenIntOrFpInductionInitialRecipe *clone() override {
+    return new VPWidenIntOrFpInductionInitialRecipe(IV, getOperand(0),
+                                                    getOperand(1), ID);
+  }
+
+  VP_CLASSOF_IMPL(VPDef::VPWidenIntOrFpInductionStartSC)
+
+  void execute(VPTransformState &State) override;
+
+#if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
+  /// Print the recipe.
+  void print(raw_ostream &O, const Twine &Indent,
+             VPSlotTracker &SlotTracker) const override;
+#endif
+
+  VPValue *getStartValue() { return getOperand(0); }
+  const VPValue *getStartValue() const { return getOperand(0); }
+
+  VPValue *getStepValue() { return getOperand(1); }
+  const VPValue *getStepValue() const { return getOperand(1); }
+
+  /// Returns the scalar type of the induction.
+  Type *getScalarType() const { return IV->getType(); }
+
+  bool onlyFirstLaneUsed(const VPValue *Op) const override {
+    assert(is_contained(operands(), Op) &&
+           "Op must be an operand of the recipe");
+    return true;
+  }
+};
+
+/// A recipe to generate the PHI of a widened IV, expanded from
+/// VPWidenIntOrFpInductionRecipe.
+class VPWidenIntOrFpInductionPHIRecipe : public VPHeaderPHIRecipe {
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lukel97 wrote:

We could reuse VPWidenPHI for this like is done in #115274 but we need to enable it on the non-native vplan path and pass through the debugloc, so I've opened up a separate PR for that in #118662 

https://github.com/llvm/llvm-project/pull/118638