spirv-opt: fix copy-propagate-arrays index opti on structs. #4891
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s-perron
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Aug 11, 2022
| result->GetMember(components); | ||
| return result; | ||
| if (!result) { | ||
| return nullptr; |
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Good change putting this fisrt.
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Copy-propagate-arrays optimization pass would create unused constants, even if the optimization not completed. This was caused by the way we handled OpAccessChain squashing: we only referenced constants, and had to create them upfront. Signed-off-by: Nathan Gauër <brioche@google.com>
s-perron
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Aug 12, 2022
s-perron
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Aug 15, 2022
As per SPIR-V spec:
OpAccessChain indices must be OpConstant when indexing into a structure.
This optimization tried to remove load cascade. But in some scenario
failed:
```c
cbuffer MyStruct {
uint my_field;
};
uint main(uint index) {
const uint my_array[1] = { my_field };
return my_array[index]
}
```
This is valid as the struct is indexed with a constant index, and then
the array is indexed using a dynamic index.
The optimization would consider the local array to be useless and
generated a load directly into the struct.
Fixes KhronosGroup#4887
Signed-off-by: Nathan Gauër <brioche@google.com>
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Looks good, but do not merge until Kokoro runs the presubmits. It seems to be slow today. |
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Thanks for the review! |
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I don't think the tests ran. When they run, there are 20 checks. This only has 2. Edit: I check the continuous build, and it does not look like anything is failing. |
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Copy-propagate-arrays optimization pass would create unused constants,
even if the optimization not completed.
This was caused by the way we handled OpAccessChain squashing: we
only referenced constants, and had to create them upfront.
For now, I couldn't find a path to reproduce this. (Might have one involving RuntimeArrays, but couldn't generate one).
This however will be more visible once #4887 is fixed since we would need to abort while computing the final OpAccessChain.
Signed-off-by: Nathan Gauër brioche@google.com