[llvm] [VPlan] Consistently use (Part, 0) for first lane scalar values (PR #80271)

[Florian Hahn via llvm-commits]

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@@ -530,8 +543,7 @@ bool VPInstruction::onlyFirstLaneUsed(const VPValue *Op) const {
   case VPInstruction::CalculateTripCountMinusVF:
   case VPInstruction::CanonicalIVIncrementForPart:
   case VPInstruction::BranchOnCount:
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fhahn wrote:

ComputeReductionResult combines the partial reduction vector values, so it should use more than the first lane per operand. It produces a single scalar value though.

https://github.com/llvm/llvm-project/pull/80271