[llvm] [VPlan] Use VPWidenIntrinsicRecipe to vp.select. (PR #110489)

[Florian Hahn via llvm-commits]

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@@ -1042,6 +1041,14 @@ StringRef VPWidenIntrinsicRecipe::getIntrinsicName() const {
   return Intrinsic::getBaseName(VectorIntrinsicID);
 }
 
+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);
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fhahn wrote:

I don't see the changes in the current version of the PR I think? Would probably be good to improve (I assume scalar arg here means we only request the first lane). If there are unrelated tests that improve, would be good to prepare a separate patch

https://github.com/llvm/llvm-project/pull/110489