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expose a way to mark cold/hot branches with llvm.expect #10137

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thestinger opened this issue Oct 29, 2013 · 3 comments
Closed

expose a way to mark cold/hot branches with llvm.expect #10137

thestinger opened this issue Oct 29, 2013 · 3 comments
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I-slow Issue: Problems and improvements with respect to performance of generated code.

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@thestinger
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There are places where this would be very useful like the slow path in a vector push method. Sadly, there's not an obvious way to expose llvm.expect because a regular Rust intrinsic becomes a function and lower-expect runs in the function pass stage.
@jdm
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jdm commented Oct 29, 2013

See #8291 where llvm.expect was turned down.

@thestinger
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@jdm: I've seen it, but I still think this is a useful feature. It's true that there are only rare use cases where it's a good idea, and I already covered most failure cases by marking the fail_ lang item as a cold.

@thestinger
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This can actually already be done with #[link_name].

flip1995 pushed a commit to flip1995/rust that referenced this issue Jan 12, 2023
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Auto merge of rust-lang#10137 - euclio:dbg-macro, r=giraffate
3816f9a 
reword dbg_macro labels

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This change rewords the `dbg_macro` lint labels to be clearer.

changelog: none
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@jdm @thestinger