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

[Ramkumar Ramachandra via llvm-commits]

================
@@ -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);
+}
+
----------------
artagnon wrote:

Thanks, added this to the commit message: "the underlying reason was that VPWidenGEP::usesScalars was too weak, and the single-scalar WidenGEP was not narrowed by narrowToSingleScalarRecipes"

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