[llvm] [LowerBufferFatPointers] Fix support for GEP T, p7, <N x T> idxs (PR #126126)

[Matt Arsenault via llvm-commits]

================
@@ -1804,14 +1804,26 @@ PtrParts SplitPtrStructs::visitGetElementPtrInst(GetElementPtrInst &GEP) {
   bool IsNUW = GEP.hasNoUnsignedWrap();
   bool IsNUSW = GEP.hasNoUnsignedSignedWrap();
 
+  StructType *ResTy = cast<StructType>(GEP.getType());
+  Type *ResRsrcTy = ResTy->getElementType(0);
+  VectorType *ResRsrcVecTy = dyn_cast<VectorType>(ResRsrcTy);
+  bool HasPtrVecIn = isa<VectorType>(Off->getType());
+  bool BroadcastsPtr = ResRsrcVecTy && !HasPtrVecIn;
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arsenm wrote:

```suggestion
  bool BroadcastsPtr = ResRsrcVecTy && !isa<VectorType>(Off->getType());
```

https://github.com/llvm/llvm-project/pull/126126