ZJIT: Allow DCE to remove some CCalls #13363
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zjit/src/cruby_methods.rs
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| /// What Type the C function returns | ||
| pub return_type: Type, | ||
| /// Whether it's legal to remove the call if the result is unused | ||
| pub is_elidable: bool, |
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"is elidable" doesn't seem to explain the actual property that makes it elidable, so things like "pure" or "side effect free" might clarify the nature better. But I'm sure sure if I like them more than "is elidable" 🤷♂️
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It can be just elidable though. leaf is not is_leaf. annotate!(..., elidable); feels more fluent to me. But it could be just me.
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It's kind of hard to describe because these kinds of operations could have side effects such as GC but we might not care. For example, allocating a 1 B element array that is unused might cause an OOM exception in the interpreter but might get deleted as unused by the compiler. I will think about this
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Ok, here's another side effect: a hypothetical HIR instruction that does a method lookup. This is actually a complicated operation, potentially, if it uses the global method lookup cache. This is a subtle side effect that we might not care about from a "should we keep it around" perspective but does require special care in code generation.
tekknolagi
changed the title
Add `elidable` field that signals that there would be no discernible effect if the call to the method were removed. The default is false.
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Add is_elidable field that signals that there would be no discernible
effect if the call to the method were removed. The default is false.