[clang] [HLSL] Fix miscompile of small structs after arrays in cbuffers (PR #179768)

[Justin Bogner via cfe-commits]

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@@ -108,9 +108,9 @@ void cbmix() {
   use(m3.y);
   // CHECK: load <2 x float>, ptr addrspace(2) getelementptr (<{ <2 x float>, target("dx.Padding", 8) }>, ptr addrspace(2) getelementptr (<{ <{ [3 x <{ <2 x float>, target("dx.Padding", 8) }>], <2 x float> }>, target("dx.Padding", 8) }>, ptr addrspace(2) @m4, i32 2, i32 0), i32 3, i32 0), align 16
   use(m4[2][3]);
-  // CHECK: load <4 x i32>, ptr addrspace(2) getelementptr inbounds nuw ([[ANON_1]], ptr addrspace(2) @m5, i32 0, i32 1), align 16
+  // CHECK: load <4 x i32>, ptr addrspace(2) getelementptr inbounds nuw ([[ANON_1]], ptr addrspace(2) @m5, i32 0, i32 2), align 16
   use(m5.d);
-  // CHECK: load <4 x i32>, ptr addrspace(2) getelementptr inbounds ([5 x <4 x i32>], ptr addrspace(2) getelementptr (<{ %ArrayAndScalar, target("dx.Padding", 12) }>, ptr addrspace(2) getelementptr inbounds nuw ([[ANON_2]], ptr addrspace(2) @m6, i32 0, i32 1), i32 2, i32 0), i32 0, i32 2), align 16
+  // CHECK: load <4 x i32>, ptr addrspace(2) getelementptr inbounds ([5 x <4 x i32>], ptr addrspace(2) getelementptr (<{ %ArrayAndScalar, target("dx.Padding", 12) }>, ptr addrspace(2) getelementptr inbounds nuw ([[ANON_2]], ptr addrspace(2) @m6, i32 0, i32 2), i32 2, i32 0), i32 0, i32 2), align 16
----------------
bogner wrote:

```c++
struct ArrayAndScalar {
  uint4 x[5];
  float y;
};

cbuffer CBMix {
  struct { int2 i; ArrayAndScalar j[4]; } m6;
};
```

Similarly, `m6.j` is found after 8 bytes of padding that follow `i`, hence member `2`.

https://github.com/llvm/llvm-project/pull/179768