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

[via llvm-commits]

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@@ -333,6 +333,9 @@ Value *VPTransformState::get(const VPValue *Def, bool NeedsScalar) {
     LastLane = 0;
   }
 
+  assert(IsSingleScalar && "must be a single-scalar at this point");
+  // We need to construct the vector value for a single-scalar value by
+  // broadcasting the scalar to all lanes.
   auto *LastInst = cast<Instruction>(get(Def, LastLane));
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ayalz wrote:

nit: better sink the definition of `LastInst` so that all comments appear together.

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