Remove 'raw' default construct insts for SPIRV emit #5556
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csyonghe
reviewed
Nov 14, 2024
| // On targets that don't support default initialization, remove 'raw' default construct | ||
| // insts because our code-gen will not have any way to emit them. | ||
| // | ||
| case CodeGenTarget::SPIRV: |
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What if the raw default constructor has uses? If we just remove them the rest of the IR will be ill-formed.
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Oh, I see the code is detecting store(var, defaultConstruct()) and remove the store along with the defaultConstruct.
csyonghe
approved these changes
Nov 14, 2024
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Our auto-diff step currently emits a few 'raw'
OpDefaultConstructinsts for intermediate data types, mostly to silence HLSL errors about uninitialized variables. This is a redundant inst, because our auto-diff pass will always make sure all generated fields are individually set.Usually, these intermediate types are made up of zero-initializable types so they get lowered to
OpMakeStruct, so targets like SPIRV whereOpDefaultConstructdoes not exist don't run into issues.For some special types, it is not easy (or safe) to emit such zero initializers, so we will instead run a pass to remove
OpDefaultConstructfor backends where it is not available (thankfully, these backends do not complain about uninitialized variables, so the code correctness is unaffected)