[llvm] [AMDGPU] Avoid crashes for non-byte-sized types in PromoteAlloca (PR #134042)

[Shilei Tian via llvm-commits]

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@@ -861,7 +868,14 @@ bool AMDGPUPromoteAllocaImpl::tryPromoteAllocaToVector(AllocaInst &Alloca) {
   LLVM_DEBUG(dbgs() << "  Attempting promotion to: " << *VectorTy << "\n");
 
   Type *VecEltTy = VectorTy->getElementType();
-  unsigned ElementSize = DL->getTypeSizeInBits(VecEltTy) / 8;
+  unsigned ElementSizeInBits = DL->getTypeSizeInBits(VecEltTy);
+  if (ElementSizeInBits != DL->getTypeAllocSizeInBits(VecEltTy)) {
+    LLVM_DEBUG(dbgs() << "  Cannot convert to vector if the allocation size "
+                         "does not match the type's size\n");
+    return false;
+  }
+  unsigned ElementSize = ElementSizeInBits / 8;
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shiltian wrote:

```suggestion
  [[maye_used]] unsigned ElementSize = ElementSizeInBits / 8;
```

https://github.com/llvm/llvm-project/pull/134042