[Merged by Bors] - [Merged by Bors] - Decouple bytecompiler from CodeBlock #2669
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Test262 conformance changes
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@@ Coverage Diff @@
## main #2669 +/- ##
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+ Coverage 49.70% 50.32% +0.62%
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Files 385 391 +6
Lines 39256 38788 -468
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+ Hits 19512 19521 +9
+ Misses 19744 19267 -477
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Razican
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Mar 15, 2023
| self.code_block.bytecode[index + 2] = bytes[1]; | ||
| self.code_block.bytecode[index + 3] = bytes[2]; | ||
| self.code_block.bytecode[index + 4] = bytes[3]; | ||
| self.bytecode[index + 1] = bytes[0]; |
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At some point we should check if this adds bound checking, and if we can do the bounds checking only once. Might enhance performance slightly.
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From my checking it seems that it does generate a bounds check per array access, my guess is that so it can give accurate panic locations if out-of-bounds
See generated assembly instructions: https://godbolt.org/z/q8azssz5K
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Explicitly checking beforehand and using a little unsafe we can remove the bounds checks: https://godbolt.org/z/bKT9ozr8s
It can create a PR after this one to address this :)
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Sometimes in Rust, if you check the full range before all the array access with an assert, it will remove all bounds checking without needing "unsafe". We would need to test that :)
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Yeah, but through by testing it doesn't seem so do so https://godbolt.org/z/q15WGh9n8 in this case...
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raskad
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Mar 15, 2023
This also give us some memory benefits, it reduces CodeBlock size from 264 => 208 (removes 56 bytes). Additionally calling `into_boxed_slice` If the vector has excess capacity, its items will be moved into a newly-allocated buffer with exactly the right capacity.
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Hopefully this is a PR in a series of PRs to implement a bytecode optimizer, before that can happen there needs to be a lot of refactoring in the way we store and compile it. This also give us some memory benefits, it reduces `CodeBlock` size from `264` **=>** `208` (removes `56` bytes). Additionally when calling `into_boxed_slice`, If the vector has excess capacity, its items will be moved into a newly-allocated buffer with exactly the right capacity removing wasted space.
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As discussed in this comment #2669 (comment), `rustc` doesn't seem to optimize out the bounds checks.
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Hopefully this is a PR in a series of PRs to implement a bytecode optimizer, before that can happen there needs to be a lot of refactoring in the way we store and compile it.
This also give us some memory benefits, it reduces
CodeBlocksize from264=>208(removes56bytes).Additionally when calling
into_boxed_slice, If the vector has excess capacity, its items will be moved into a newly-allocated buffer with exactly the right capacity removing wasted space.