[llvm] [SLP] Fix crash of shuffle poison (PR #106857)

[Alexey Bataev via llvm-commits]

alexey-bataev wrote:

Imean, something like this:
```
diff --git a/llvm/lib/Transforms/Vectorize/SLPVectorizer.cpp b/llvm/lib/Transforms/Vectorize/SLPVectorizer.cpp
index b7bcfba7f86d..993fd6ab1b0b 100644
--- a/llvm/lib/Transforms/Vectorize/SLPVectorizer.cpp
+++ b/llvm/lib/Transforms/Vectorize/SLPVectorizer.cpp
@@ -11204,6 +11204,10 @@ BoUpSLP::tryToGatherSingleRegisterExtractElements(
       UndefVectorExtracts.push_back(I);
       continue;
     }
+    if (Idx >= VecTy->getNumElements()) {
+      UndefVectorExtracts.push_back(I);
+      continue;
+    }
     SmallBitVector ExtractMask(VecTy->getNumElements(), true);
     ExtractMask.reset(*Idx);
     if (isUndefVector(EI->getVectorOperand(), ExtractMask).all()) {
@@ -11251,7 +11255,7 @@ BoUpSLP::tryToGatherSingleRegisterExtractElements(
   // shuffle of a single/two vectors the scalars are extracted from.
   std::optional<TTI::ShuffleKind> Res =
       isFixedVectorShuffle(GatheredExtracts, Mask);
-  if (!Res) {
+  if (!Res || all_of(Mask, [](int Idx) { return Idx == PoisonMaskElem; })) {
     // TODO: try to check other subsets if possible.
     // Restore the original VL if attempt was not successful.
     copy(SavedVL, VL.begin());

```

https://github.com/llvm/llvm-project/pull/106857