[LV] Check VPValue operand instead of Cost::isUniformAfterVec (NFC).

ILV::scalarizeInstruction still uses the original IR operands to check
if an input value is uniform after vectorization.

There is no need to go back to the cost model to figure that out, as the
information is already explicit in the VPlan. Just check directly
whether the VPValue is defined outside the plan or is a uniform
VPReplicateRecipe.

Reviewed By: Ayal

Differential Revision: https://reviews.llvm.org/D114253

Author: fhahn

llvm/lib/Transforms/Vectorize/LoopVectorize.cpp

@@ -3030,14 +3030,12 @@ void InnerLoopVectorizer::scalarizeInstruction(Instruction *Instr,
                                Builder.GetInsertPoint());
   // Replace the operands of the cloned instructions with their scalar
   // equivalents in the new loop.
-  for (unsigned op = 0, e = RepRecipe->getNumOperands(); op != e; ++op) {
-    auto *Operand = dyn_cast<Instruction>(Instr->getOperand(op));
+  for (auto &I : enumerate(RepRecipe->operands())) {
     auto InputInstance = Instance;
-    if (!Operand || !OrigLoop->contains(Operand) ||
-        (Cost->isUniformAfterVectorization(Operand, State.VF)))
+    VPValue *Operand = I.value();
+    if (State.Plan->isUniformAfterVectorization(Operand))
       InputInstance.Lane = VPLane::getFirstLane();
-    auto *NewOp = State.get(RepRecipe->getOperand(op), InputInstance);
-    Cloned->setOperand(op, NewOp);
+    Cloned->setOperand(I.index(), State.get(Operand, InputInstance));
   }
   addNewMetadata(Cloned, Instr);
 

llvm/lib/Transforms/Vectorize/VPlan.h

@@ -2255,6 +2255,12 @@ class VPlan {
     return map_range(Operands, Fn);
   }
 
+  /// Returns true if \p VPV is uniform after vectorization.
+  bool isUniformAfterVectorization(VPValue *VPV) const {
+    auto RepR = dyn_cast_or_null<VPReplicateRecipe>(VPV->getDef());
+    return !VPV->getDef() || (RepR && RepR->isUniform());
+  }
+
 private:
   /// Add to the given dominator tree the header block and every new basic block
   /// that was created between it and the latch block, inclusive.