[llvm] [VPlan] Explicitly replicate VPInstructions by VF. (PR #155102)

[via llvm-commits]

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@@ -1244,6 +1223,9 @@ bool VPInstruction::onlyFirstLaneUsed(const VPValue *Op) const {
   case VPInstruction::Broadcast:
   case VPInstruction::ReductionStartVector:
     return true;
+  case VPInstruction::BuildStructVector:
+  case VPInstruction::BuildVector:
+    return getNumOperands() > 1;
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ayalz wrote:

and this determines if `onlyFirstLaneUsed` or not? Worth a comment.

https://github.com/llvm/llvm-project/pull/155102