[llvm] Reland [VPlan] Handle WidenGEP in narrowToSingleScalars (PR #167880)

[Florian Hahn via llvm-commits]

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@@ -2516,6 +2516,11 @@ void VPScalarIVStepsRecipe::print(raw_ostream &O, const Twine &Indent,
 }
 #endif
 
+bool VPWidenGEPRecipe::usesFirstLaneOnly(const VPValue *Op) const {
+  assert(is_contained(operands(), Op) && "Op must be an operand of the recipe");
+  return vputils::isSingleScalar(Op);
+}
+
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fhahn wrote:

Could you add what assertion got triggered? It is not immediately clear to me how this prevents assertions.

https://github.com/llvm/llvm-project/pull/167880