Outline the drain to heap logic in TinyVec::push#127
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Lokathor merged 2 commits intoLokathor:mainfrom Jan 14, 2021
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Shnatsel
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Jan 13, 2021
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| if let Some(x) = arr.try_push(val) { | ||
| #[inline(never)] | ||
| fn drain_to_heap_and_push<A: Array>( |
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You can also try #[cold] annotation, this should provide branch predictor hints for the match below.
Also, could you add a comment explaining why this code is in a separate function?
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A comment would be good about what's going on here.
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I'm unable to measure a difference between #[inline(never)] and #[cold]. I've opted for #[cold] on the basis that if the optimizer somehow concludes that this function is profitable to inline, that is permitted.
Lokathor
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Jan 13, 2021
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Looks good. @saethlin i can merge this if you're satisfied. |
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@Lokathor Yes please |
saethlin
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Jan 16, 2021
add comparison script Outline the drain to heap logic in TinyVec::push Outline the drain to heap logic in TinyVec::push Use #[cold] and explain the outlining in a comment change gen_remove to rebuild sample Vec with clone instead of push rename outer vec in gen_remove for clarity Swap each element instead of calling rotate_left add more loops to amortize away startup cost, tune tinyvec impls a bit swap instead of rotate_right, explain in comment drop loops again wheee Outline the drain to heap logic in TinyVec::push (Lokathor#127) * Outline the drain to heap logic in TinyVec::push * Use #[cold] and explain the outlining in a comment Swap each element instead of calling rotate_left (Lokathor#128)
saethlin
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Jan 19, 2021
add comparison script Outline the drain to heap logic in TinyVec::push Outline the drain to heap logic in TinyVec::push Use #[cold] and explain the outlining in a comment change gen_remove to rebuild sample Vec with clone instead of push rename outer vec in gen_remove for clarity Swap each element instead of calling rotate_left add more loops to amortize away startup cost, tune tinyvec impls a bit swap instead of rotate_right, explain in comment drop loops again wheee Outline the drain to heap logic in TinyVec::push (Lokathor#127) * Outline the drain to heap logic in TinyVec::push * Use #[cold] and explain the outlining in a comment Swap each element instead of calling rotate_left (Lokathor#128)
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Per #39
This is a strategy I've seen be very useful in other places; keeping code size down by forcibly outlining algorithmically cold paths tends to make a huge difference.