Restore HashMap performance by allowing some functions to be inlined #25070
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Since the hashmap and its hasher are implemented in different crates, we currently can't benefit from inlining, which means that especially for small, fixed size keys, there is a huge overhead in hash calculations, because the compiler can't apply optimizations that only apply for these keys. Fixes the brainfuck benchmark in rust-lang#24014.
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| @@ -120,6 +121,7 @@ impl SipHasher { | |||
| self.ntail = 0; | |||
| } | |||
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| #[inline] | |||
| fn write(&mut self, msg: &[u8]) { | |||
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Hm, it's unfortunate that this function is so large.
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Yeah, but that's also the most important function to have available for inlining, because most of it is thrown away when the compiler sees that, for example, it's only called with once with a single 8 byte slice. See my remark below about `#[inline(Maybe)].
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For the record, I wonder whether we might want a |
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#6616 is relevant. :) |
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Since the hashmap and its hasher are implemented in different crates, we currently can't benefit from inlining, which means that especially for small, fixed size keys, there is a huge overhead in hash calculations, because the compiler can't apply optimizations that only apply for these keys. Fixes the brainfuck benchmark in #24014.
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Since the hashmap and its hasher are implemented in different crates, we
currently can't benefit from inlining, which means that especially for
small, fixed size keys, there is a huge overhead in hash calculations,
because the compiler can't apply optimizations that only apply for these
keys.
Fixes the brainfuck benchmark in #24014.