[llvm] [VectorUtils][VPlan] Consolidate VPWidenIntrinsicRecipe::onlyFirstLaneUsed and isVectorIntrinsicWithScalarOpAtArg (PR #137497)

[Florian Hahn via llvm-commits]

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@@ -1373,10 +1373,8 @@ StringRef VPWidenIntrinsicRecipe::getIntrinsicName() const {
 
 bool VPWidenIntrinsicRecipe::onlyFirstLaneUsed(const VPValue *Op) const {
   assert(is_contained(operands(), Op) && "Op must be an operand of the recipe");
-  // Vector predication intrinsics only demand the the first lane the last
-  // operand (the EVL operand).
-  return VPIntrinsic::isVPIntrinsic(VectorIntrinsicID) &&
-         Op == getOperand(getNumOperands() - 1);
+  unsigned Idx = std::distance(op_begin(), find(operands(), Op));
+  return isVectorIntrinsicWithScalarOpAtArg(VectorIntrinsicID, Idx, nullptr);
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fhahn wrote:

Can you add a test for the new behavior?

https://github.com/llvm/llvm-project/pull/137497