[wgsl-in] [spv-out] Missing OpName for let declaration used as output?

[bielok]

I was expecting that writing a let declaration and immediatly returning that as the output should retain the identifier name as a OpName when translating wgsl to spv with the following flags:

let mut flags = spv::WriterFlags::LABEL_VARYINGS;
flags.set(spv::WriterFlags::DEBUG, true);

Is this not the case? If so, why?

I am still getting acquainted with both naga and SPIR-V, excuse the silly question 🙏

SPIR-V disassembly (includes WGSL source)

; SPIR-V
; Version: 1.1
; Generator: Khronos; 28
; Bound: 15
; Schema: 0
               OpCapability Shader
          %1 = OpExtInstImport "GLSL.std.450"
               OpMemoryModel Logical GLSL450
               OpEntryPoint Fragment %main_fs "main_fs" %7
               OpExecutionMode %main_fs OriginUpperLeft
          %3 = OpString "input.wgsl"
               OpSource WGSL 0 %3 "@fragment
fn main_fs() -> @location(0) vec4<f32> {
    let outColor = vec4<f32>(35.0, 1.0, 1.0, 1.0);
    return outColor;
}"
               OpName %main_fs "main_fs"
               OpDecorate %7 Location 0
       %void = OpTypeVoid
      %float = OpTypeFloat 32
    %v4float = OpTypeVector %float 4
%_ptr_Output_v4float = OpTypePointer Output %v4float
          %7 = OpVariable %_ptr_Output_v4float Output
         %10 = OpTypeFunction %void
   %float_35 = OpConstant %float 35
    %float_1 = OpConstant %float 1
         %13 = OpConstantComposite %v4float %float_35 %float_1 %float_1 %float_1
    %main_fs = OpFunction %void None %10
          %6 = OpLabel
               OpBranch %14
         %14 = OpLabel
               OpLine %3 3 20
               OpStore %7 %13
               OpReturn
               OpFunctionEnd

Now consider the same case, but replacing let with var...

; SPIR-V
; Version: 1.1
; Generator: Khronos; 28
; Bound: 18
; Schema: 0
               OpCapability Shader
          %1 = OpExtInstImport "GLSL.std.450"
               OpMemoryModel Logical GLSL450
               OpEntryPoint Fragment %main_fs "main_fs" %7
               OpExecutionMode %main_fs OriginUpperLeft
          %3 = OpString "input.wgsl"
               OpSource WGSL 0 %3 "@fragment
fn main_fs() -> @location(0) vec4<f32> {
    var outColor = vec4<f32>(35.0, 1.0, 1.0, 1.0);
    return outColor;
}"
               OpName %main_fs "main_fs"
               OpName %outColor "outColor"
               OpDecorate %7 Location 0
       %void = OpTypeVoid
      %float = OpTypeFloat 32
    %v4float = OpTypeVector %float 4
%_ptr_Output_v4float = OpTypePointer Output %v4float
          %7 = OpVariable %_ptr_Output_v4float Output
         %10 = OpTypeFunction %void
   %float_35 = OpConstant %float 35
    %float_1 = OpConstant %float 1
         %13 = OpConstantComposite %v4float %float_35 %float_1 %float_1 %float_1
%_ptr_Function_v4float = OpTypePointer Function %v4float
    %main_fs = OpFunction %void None %10
          %6 = OpLabel
   %outColor = OpVariable %_ptr_Function_v4float Function %13
               OpBranch %16
         %16 = OpLabel
               OpLine %3 3 20
               OpLine %3 1 1
         %17 = OpLoad %v4float %outColor
               OpStore %7 %17
               OpReturn
               OpFunctionEnd

Notice that OpName %outColor "outColor" is indeed emitted.

Actually, I was trying to obtain the following:

%outColor = OpVariable %_ptr_Output_v4float Output

And instead got

%outColor = OpVariable %_ptr_Function_v4float Function %13