perf: optimize ScopeData structure #1370
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littledivy
commented
Dec 1, 2023
littledivy
commented
aapoalas
approved these changes
Dec 1, 2023
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Did I just bring back the Rust compiler bug we had earlier? 👀 #1229 https://github.com/denoland/rusty_v8/actions/runs/7057713260/job/19212435294?pr=1370#step:11:7270 |
mmastrac
reviewed
Dec 1, 2023
| enum ScopeStatus { | ||
| Free, | ||
| Current { zombie: bool }, | ||
| Shadowed { zombie: bool }, | ||
| CurrentZombie, |
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If we #[cfg(debug_assertions)] here, the compiler may have more opportunities to optimize out the zombie code in release mode.
mmastrac
reviewed
Dec 1, 2023
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| match self_mut.status { | ||
| ScopeStatus::CurrentZombie | ScopeStatus::CurrentNoZombie => self_mut, | ||
| _ => unreachable!(), | ||
| } |
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While we're in here, can we convert this match/unreachable pattern to a debug_assert?
mmastrac
reviewed
Dec 1, 2023
| @@ -1811,7 +1817,6 @@ pub(crate) mod data { | |||
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| #[derive(Debug)] | |||
| enum ScopeTypeSpecificData { | |||
| None, | |||
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Does Rust use the niche with Option? Is it the same size as ScopeTypeSpecificData?
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Testing w/ASAN and opt-level=1. It's possible this is good to go and was just miscompiling. |
| @@ -1295,13 +1295,13 @@ pub(crate) mod data { | |||
| previous: Option<NonNull<ScopeData>>, | |||
| next: Option<Box<ScopeData>>, | |||
| // The 'status' field is also always valid (but does change). | |||
| status: Cell<ScopeStatus>, | |||
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