where available use AtomicU{64,128} instead of mutex for Instant backsliding protection
This decreases the overhead of backsliding protection on x86 systems with unreliable TSC, e.g. windows. And on aarch64 systems where 128bit atomics are available.
The following benchmarks were taken on x86_64 linux though by overriding `actually_monotonic()`, the numbers may look different on other platforms
```
# actually_monotonic() == true
test time::tests::instant_contention_01_threads ... bench: 44 ns/iter (+/- 0)
test time::tests::instant_contention_02_threads ... bench: 44 ns/iter (+/- 0)
test time::tests::instant_contention_04_threads ... bench: 44 ns/iter (+/- 0)
test time::tests::instant_contention_08_threads ... bench: 44 ns/iter (+/- 0)
test time::tests::instant_contention_16_threads ... bench: 44 ns/iter (+/- 0)
# 1x AtomicU64
test time::tests::instant_contention_01_threads ... bench: 65 ns/iter (+/- 0)
test time::tests::instant_contention_02_threads ... bench: 157 ns/iter (+/- 20)
test time::tests::instant_contention_04_threads ... bench: 281 ns/iter (+/- 53)
test time::tests::instant_contention_08_threads ... bench: 555 ns/iter (+/- 77)
test time::tests::instant_contention_16_threads ... bench: 883 ns/iter (+/- 107)
# mutex
test time::tests::instant_contention_01_threads ... bench: 60 ns/iter (+/- 2)
test time::tests::instant_contention_02_threads ... bench: 770 ns/iter (+/- 231)
test time::tests::instant_contention_04_threads ... bench: 1,347 ns/iter (+/- 45)
test time::tests::instant_contention_08_threads ... bench: 2,693 ns/iter (+/- 114)
test time::tests::instant_contention_16_threads ... bench: 5,244 ns/iter (+/- 487)
```
Since I don't have an arm machine with 128bit atomics I wasn't able to benchmark the AtomicU128 implementation.
I/O safety.
Introduce `OwnedFd` and `BorrowedFd`, and the `AsFd` trait, and
implementations of `AsFd`, `From<OwnedFd>` and `From<T> for OwnedFd`
for relevant types, along with Windows counterparts for handles and
sockets.
Tracking issue: <https://github.com/rust-lang/rust/issues/87074>
RFC: <https://github.com/rust-lang/rfcs/blob/master/text/3128-io-safety.md>
Highlights:
- The doc comments at the top of library/std/src/os/unix/io/mod.rs and library/std/src/os/windows/io/mod.rs
- The new types and traits in library/std/src/os/unix/io/fd.rs and library/std/src/os/windows/io/handle.rs
- The removal of the `RawHandle` struct the Windows impl, which had the same name as the `RawHandle` type alias, and its functionality is now folded into `Handle`.
Managing five levels of wrapping (File wraps sys::fs::File wraps sys::fs::FileDesc wraps OwnedFd wraps RawFd, etc.) made for a fair amount of churn and verbose as/into/from sequences in some places. I've managed to simplify some of them, but I'm open to ideas here.
r? `@joshtriplett`
Fix compiling other codegen backends when llvm is enabled
Extracted from #81746
Without this change rustbuild will not pass the required linker argument to find libllvm. While other backends likely don't use libllvm, it is necessary to be able to link against rustc_driver as the llvm backend is linked into it.
Add fast path for Path::cmp that skips over long shared prefixes
```
# before
test path::tests::bench_path_cmp_fast_path_buf_sort ... bench: 60,811 ns/iter (+/- 865)
test path::tests::bench_path_cmp_fast_path_long ... bench: 6,459 ns/iter (+/- 275)
test path::tests::bench_path_cmp_fast_path_short ... bench: 1,777 ns/iter (+/- 34)
# after
test path::tests::bench_path_cmp_fast_path_buf_sort ... bench: 38,140 ns/iter (+/- 211)
test path::tests::bench_path_cmp_fast_path_long ... bench: 1,471 ns/iter (+/- 24)
test path::tests::bench_path_cmp_fast_path_short ... bench: 1,106 ns/iter (+/- 9)
```
RFC2229 Only compute place if upvars can be resolved
Closes https://github.com/rust-lang/rust/issues/87987
This PR fixes an ICE when trying to unwrap an Err. This error appears when trying to convert a PlaceBuilder into Place when upvars can't yet be resolved. We should only try to convert a PlaceBuilder into Place if upvars can be resolved.
r? `@nikomatsakis`
RFC2229 Add missing edge case
Closes https://github.com/rust-lang/rust/issues/87988
This PR fixes an ICE where a match discriminant is not being read when expected. This ICE was the result of a missing edge case which assumed that if a pattern is of type `PatKind::TupleStruct(..) | PatKind::Path(..) | PatKind::Struct(..) | PatKind::Tuple(..)` then a place could only be a multi variant if the place is of type kind Adt.
We used to avoid doing this because we didn't want to make coercion depend on
the state of inference. For better or worse, we have moved away from this
position over time. Therefore, I am going to go ahead and resolve the `b`
target type early on so that it is done uniformly.
(The older technique for managing this was always something of a hack
regardless; if we really wanted to avoid integrating coercion and inference we
needed to be more disciplined about it.)
The name (and updated documentation) make the FFI-only usage clearer, and wrapping Option<OwnedHandle> avoids the need to write a separate Drop or Debug impl.
Co-authored-by: Josh Triplett <josh@joshtriplett.org>
