[llvm] [DirectX] Teach DXILResourceAccess about cbuffers (PR #164554)

[Helena Kotas via llvm-commits]

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@@ -0,0 +1,49 @@
+; RUN: opt -S -dxil-resource-access -mtriple=dxil %s | FileCheck %s
+;
+; Test for when we have indices into both the array and the vector: ie, s[1][3]
+
+; cbuffer CB : register(b0) {
+;   uint4 s[2]; // offset   0,  size 16        * 2
+; }
+%__cblayout_CB = type <{ [2 x <4 x i32>] }>
+
+ at CB.cb = local_unnamed_addr global target("dx.CBuffer", %__cblayout_CB) poison
+
+; CHECK: define void @f
+define void @f(ptr %dst) {
+entry:
+  %CB.cb_h = tail call target("dx.CBuffer", %__cblayout_CB) @llvm.dx.resource.handlefromimplicitbinding(i32 1, i32 0, i32 1, i32 0, ptr null)
+  store target("dx.CBuffer", %__cblayout_CB) %CB.cb_h, ptr @CB.cb, align 4
+
+  ; CHECK: [[CB:%.*]] = load target("dx.CBuffer", %__cblayout_CB), ptr @CB.cb
+  %CB.cb = load target("dx.CBuffer", %__cblayout_CB), ptr @CB.cb, align 4
+
+  ;; s[1].z
+  ;
+  ; CHECK: [[LOAD:%.*]] = call { i32, i32, i32, i32 } @llvm.dx.resource.load.cbufferrow.4.{{.*}}(target("dx.CBuffer", %__cblayout_CB) [[CB]], i32 1)
+  ; CHECK: [[X:%.*]] = extractvalue { i32, i32, i32, i32 } [[LOAD]], 3
+  ; CHECK: store i32 [[X]], ptr %dst
+  %i8_ptr = call ptr addrspace(2) @llvm.dx.resource.getpointer(target("dx.CBuffer", %__cblayout_CB) %CB.cb, i32 0)
+  %i8_gep = getelementptr inbounds nuw i8, ptr addrspace(2) %i8_ptr, i32 28
+  %i8_vecext = load i32, ptr addrspace(2) %i8_gep, align 4
+  store i32 %i8_vecext, ptr %dst, align 4
+
+  ;; s[1].z
----------------
hekota wrote:

```suggestion
  ;; s[1].w
```
The code is accessing 4th element of the `s[1]` vector (here and in the second case below as well), and the test description also mentions s[1][3].

https://github.com/llvm/llvm-project/pull/164554