[llvm] [LV] Convert gather loads with invariant stride into strided loads (PR #147297)

[Florian Hahn via llvm-commits]

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@@ -4204,3 +4212,184 @@ void VPlanTransforms::addBranchWeightToMiddleTerminator(
       MDB.createBranchWeights({1, VectorStep - 1}, /*IsExpected=*/false);
   MiddleTerm->addMetadata(LLVMContext::MD_prof, BranchWeights);
 }
+
+static std::pair<VPValue *, VPValue *> matchStridedStart(VPValue *CurIndex) {
+  // TODO: Support VPWidenPointerInductionRecipe.
+  if (auto *WidenIV = dyn_cast<VPWidenIntOrFpInductionRecipe>(CurIndex))
+    return {WidenIV, WidenIV->getStepValue()};
+
+  auto *WidenR = dyn_cast<VPWidenRecipe>(CurIndex);
+  if (!WidenR || !CurIndex->getUnderlyingValue())
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fhahn wrote:

Why do we require an underlying value?

https://github.com/llvm/llvm-project/pull/147297