std: Improve codegen size of accessing TLS #55518
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src/libstd/thread/local.rs
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| (*ptr).as_ref().unwrap() | ||
| match *ptr { | ||
| Some(ref x) => x, | ||
| None => intrinsics::unreachable(), |
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I think this really deserves a comment indicating why it was done -- could you add one? That way we can avoid confusion or cleanup removing this without knowing what to check
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Also don't we have unreachable_unchecked so that we do not have to call an intrinsic directly?
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@bors r- Failed in #55579 (comment) |
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kennytm
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Nov 1, 2018
No need for this to actually show up in optimized non-LTO executables!
Some code in the TLS implementation in libstd stores `Some(val)` into an `&mut Option<T>` (effectively) and then pulls out `&T`, but it currently uses `.unwrap()` which can codegen into a panic even though it can never panic. With sufficient optimizations enabled (like LTO) the compiler can see through this but this commit helps it along in normal mode (`--release` with Cargo by default) to avoid codegen'ing the panic path. This ends up improving the optimized codegen on wasm by ensuring that a call to panic pulling in more file size doesn't stick around.
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@bors: retry Seems spurious ... |
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std: Improve codegen size of accessing TLS Some code in the TLS implementation in libstd stores `Some(val)` into an `&mut Option<T>` (effectively) and then pulls out `&T`, but it currently uses `.unwrap()` which can codegen into a panic even though it can never panic. With sufficient optimizations enabled (like LTO) the compiler can see through this but this commit helps it along in normal mode (`--release` with Cargo by default) to avoid codegen'ing the panic path. This ends up improving the optimized codegen on wasm by ensuring that a call to panic pulling in more file size doesn't stick around.
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The job Click to expand the log.I'm a bot! I can only do what humans tell me to, so if this was not helpful or you have suggestions for improvements, please ping or otherwise contact |
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Nov 5, 2018
std: Improve codegen size of accessing TLS Some code in the TLS implementation in libstd stores `Some(val)` into an `&mut Option<T>` (effectively) and then pulls out `&T`, but it currently uses `.unwrap()` which can codegen into a panic even though it can never panic. With sufficient optimizations enabled (like LTO) the compiler can see through this but this commit helps it along in normal mode (`--release` with Cargo by default) to avoid codegen'ing the panic path. This ends up improving the optimized codegen on wasm by ensuring that a call to panic pulling in more file size doesn't stick around.
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@bors: retry 3 hr timeout |
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Nov 6, 2018
std: Improve codegen size of accessing TLS Some code in the TLS implementation in libstd stores `Some(val)` into an `&mut Option<T>` (effectively) and then pulls out `&T`, but it currently uses `.unwrap()` which can codegen into a panic even though it can never panic. With sufficient optimizations enabled (like LTO) the compiler can see through this but this commit helps it along in normal mode (`--release` with Cargo by default) to avoid codegen'ing the panic path. This ends up improving the optimized codegen on wasm by ensuring that a call to panic pulling in more file size doesn't stick around.
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☀️ Test successful - status-appveyor, status-travis |
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Some code in the TLS implementation in libstd stores
Some(val)into an&mut Option<T>(effectively) and then pulls out&T, but it currentlyuses
.unwrap()which can codegen into a panic even though it can neverpanic. With sufficient optimizations enabled (like LTO) the compiler can
see through this but this commit helps it along in normal mode
(
--releasewith Cargo by default) to avoid codegen'ing the panic path.This ends up improving the optimized codegen on wasm by ensuring that a
call to panic pulling in more file size doesn't stick around.