[llvm] [mlir] [AMDGPU][Verifier] Check address space of `alloca` instruction (PR #135820)

[Matt Arsenault via llvm-commits]

================
@@ -4395,6 +4395,11 @@ void Verifier::visitAllocaInst(AllocaInst &AI) {
     verifySwiftErrorValue(&AI);
   }
 
+  if (TT.isAMDGPU()) {
+    Check(AI.getAddressSpace() == AMDGPUAS::PRIVATE_ADDRESS,
+          "alloca on amdgpu must be in addrspace(5)", &AI);
----------------
arsenm wrote:

The problem with that is the datalayout isn't always right. Even if you have the triple, the right datalaoyut doesn't get pulled. e.g.

```
; RUN llvm-as < %s
target triple = "amdgcn-amd-amdhsa"

define void @foo() {
  %alloca = alloca i32
  store volatile i32 0, ptr %alloca
  ret void
}
```

In this case DL.getAllocaAddrSpace() is 0 

https://github.com/llvm/llvm-project/pull/135820