[llvm] [VPlan] Handle single-scalar conds in VPWidenSelectRecipe. (PR #165506)

[via llvm-commits]

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@@ -659,7 +659,9 @@ Value *VPInstruction::generate(VPTransformState &State) {
   }
   case Instruction::Select: {
     bool OnlyFirstLaneUsed = vputils::onlyFirstLaneUsed(this);
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ayalz wrote:

The usage of OnlyFirstLaneUsed here and elsewhere deserves rethinking, its usage here essentially asks if the recipe deals with single scalar operands (and result), rather than using only first lanes if multiple lanes are provided.

https://github.com/llvm/llvm-project/pull/165506