[llvm] [AMDGPU] Restrict promote alloca on pointers across address spaces (PR #119762)

[Matt Arsenault via llvm-commits]

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@@ -674,7 +674,17 @@ static bool isSupportedAccessType(FixedVectorType *VecTy, Type *AccessTy,
   //
   // We could handle more complicated cases, but it'd make things a lot more
   // complicated.
-  if (isa<FixedVectorType>(AccessTy)) {
+
+  // If both are pointer types, verify if they are compatible to copy across
+  // address spaces.
+  bool canCopyAcrossAddressSpaces = true;
+  if (AccessTy->isPtrOrPtrVectorTy() && VecTy->isPtrOrPtrVectorTy()) {
+    if (DL.getPointerSize(AccessTy->getPointerAddressSpace()) !=
+        DL.getPointerSize(VecTy->getPointerAddressSpace()))
+      canCopyAcrossAddressSpaces = false;
+  }
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arsenm wrote:

There is no copy across address spaces here, this check is conceptually wrong. You only need to verify the size is compatible. For the final code emission, you'll need to insert no-op casts to get the types to match 

https://github.com/llvm/llvm-project/pull/119762