-keep-all-resources option to preserve optimized-out resources in DXIL reflection #7734
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…lection. This isn't default to avoid DXIL bloat and because apps might assume that if a resource is missing that it's optimized out and use this info to avoid transitions or other optimizations. When a resource is unused but still present, it won't emit a createHandle, but the reflection info will still be there
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✅ With the latest revision this PR passed the C/C++ code formatter. |
…this pc has a bit of trouble to get the tests to run, switching to my other pc first to verify
…ll resources should keep it in the runtime data, but remove them from functions that don't use them
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Okay, now that I've sacrificed a couple of goats, I've been able to get the HLSL tests to run. Fixed a little issue in my test. Runs fine now. |
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/AzurePipelines run |
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Commenter does not have sufficient privileges for PR 7734 in repo microsoft/DirectXShaderCompiler |
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Actually it turns out this is quite a bit more complicated than it first seems. |
…istent bindings it actually affects behavior in reflection, so it needs to be persistent. Added DxilModule::RemoveEmptyBuffers to handle removal of empty $Globals buffer. Added a proper test to check for optimized out registers with the correct flag or non optimized out registers.
…ag added to DxilResourceBase; m_IsUnused. This is packed in the highest bit of the id stored to disk. This is used so that ID3D12ShaderReflection can also figure out if something is really unused. This means that ID3D12LibraryReflection could technically figure out two things if we wanted to; if a register is unused top level (so in all functions) and if a register is unused for a specific function. For ID3D12LibraryReflection it's just kept function local and for ID3D12ShaderReflection it's kept global. Added unit test for ID3D12ShaderReflection.
…iler into keep_all_resources
…ing a register. Fixed a wrong scope creating multiple functions of the same type by accident.
…serve in this branch. Added release note
…ilShaderFlags instead. This is because 'keep-all' from the other PR relies on this Enum to be serialized; because reflection needs to know if unused resources are preserved.
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This change introduces a new compiler option, -keep-all-resources, which ensures that even optimized-out resources are retained in DXIL reflection.
Motivation
By default, unused resources are removed during optimization, and applications may rely on their absence to infer optimization opportunities (e.g., skipping transitions). However, sometimes when reflection completeness is important (e.g., tools, debugging, visual scripting, or consistency with SPIR-V -Od) it is desirable to keep all declared resources visible in reflection, regardless of usage.
Behavior
When enabled, unused resources are not fully removed.
They will appear in reflection but will not generate createHandle instructions.
Notes
This is not enabled by default to avoid DXIL bloat and to prevent breaking apps that assume missing resources imply optimization.
Conflicts with #7729.
Step 2/2 to solve #5105.