[llvm] [SLP]Allow matching and shuffling of extractelement vector operands with different VF. (PR #97414)

[Simon Pilgrim via llvm-commits]

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@@ -10679,11 +10667,11 @@ BoUpSLP::tryToGatherSingleRegisterExtractElements(
   SmallVector<Value *> GatheredExtracts(
       VL.size(), PoisonValue::get(VL.front()->getType()));
   if (SingleMax >= PairMax && SingleMax) {
-    for (int Idx : VectorOpToIdx[SingleVec])
+    for (int Idx : Vectors.front().second)
       std::swap(GatheredExtracts[Idx], VL[Idx]);
-  } else {
-    for (Value *V : {PairVec.first, PairVec.second})
-      for (int Idx : VectorOpToIdx[V])
+  } else if (!Vectors.empty()) {
+    for (unsigned Idx : {0, 1})
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RKSimon wrote:

why can we guarantee that Vectors.size() == 2 here (but not earlier)?

https://github.com/llvm/llvm-project/pull/97414