Templated structs have invalid debug info.

[adam-yang]

Description

The debug value mapping for templated structs map to the pointer of the struct, instead of the value of the struct.

Steps to Reproduce

Compile the following shader:

// /T ps_6_0 /Zi /Od
template<typename T>
struct S {
  T a, b;
  T Get() {
    return a + b;
  }
};


[RootSignature("")]
float main(float x : X, float y : Y, float z : Z, float w : W) : SV_Target {
  S<float> s;
  s.a = x;
  s.b = y;
  return s.Get();
}

Actual Behavior

You will see that the member b of variable s has the following mapping:

call void @llvm.dbg.value(metadata float %0, i64 0, metadata !53, metadata !58), !dbg !55 ; var:"this" !DIExpression(DW_OP_bit_piece, 32, 32) func:"Get"
!53 = !DILocalVariable(tag: DW_TAG_arg_variable, name: "this", arg: 1, scope: !8, type: !54)
!54 = !DIDerivedType(tag: DW_TAG_pointer_type, baseType: !9, size: 32, align: 32)
!9 = !DICompositeType(tag: DW_TAG_structure_type, name: "S<float>", file: !1, line: 4, size: 64, align: 32, elements: !10, templateParams: !17)

The expected behaviour should be that this variable should be a value type, like so:

call void @llvm.dbg.value(metadata float %0, i64 0, metadata !51, metadata !55), !dbg !52 ; var:"this" !DIExpression(DW_OP_bit_piece, 32, 32) func:"Get"
!51 = !DILocalVariable(tag: DW_TAG_arg_variable, name: "this", arg: 1, scope: !8, type: !9)
!9 = !DICompositeType(tag: DW_TAG_structure_type, name: "S", file: !1, line: 11, size: 64, align: 32, elements: !10)

(This was done by compiling a non-templated version of struct S)

Environment

• DXC version: Nightly
• Host Operating System: Windows 11