[SPIR-V] generated SPIR-V is invalid: Result type (OpTypeStruct) does not match the type that results from indexing into the composite (OpTypeStruct).

[alexandreLBarrett]

Description
While trying to compile my shader for SPIR-V I get an error regarding two OpTypeStruct that don't match. I get it when trying to assigning a ConstantBuffer to a T in the shader. See Godbolt link for more details.

Steps to Reproduce
See Godbolt link: https://godbolt.org/z/vT9jzazfr

It seems related to the fact there is a nested struct inside another struct used in a ConstantBuffer. They are then incompatible.

Actual Behavior

fatal error: generated SPIR-V is invalid: Result type (OpTypeStruct) does not match the type that results from indexing into the composite (OpTypeStruct).
  %33 = OpCompositeExtract %DirectionalLight_0 %32 0

Environment

• DXC version 1.8.2505 (Godbolt link), also on 1.9.2602
• Host Operating System: Windows 11 25H2

[s-perron]

The problem is that the result of the extract expects a type that is not explicitly laidout, but the input type is explicitly laidout. Somewhere we are not propagating the layout type correctly when generating the spir-v.

               OpMemberDecorate %DirectionalLight 0 Offset 0
               OpMemberDecorate %DirectionalLight 1 Offset 12
               OpMemberDecorate %DirectionalLight 2 Offset 16
...
%type_ConstantBuffer_Scene = OpTypeStruct %DirectionalLight
...
         %32 = OpLoad %type_ConstantBuffer_Scene %31
         %33 = OpCompositeExtract %DirectionalLight_0 %32 0

[luciechoi]

This issue is fixed, please try recompiling from head or wait for the next DXC release

[luciechoi]

Reopened as there are more fixes to be made for the issue. The outputted SPIR-V doesn't pass the SPIR-V validator

NVM! the HLSL should now compile successfully, and spir-v validator does run by default (it was the -fcgl flag that failed the validation).