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Optimize is_main_thread by using a libc call #616

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May 21, 2024
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Optimize is_main_thread by using a libc call #616

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33 changes: 31 additions & 2 deletions framework-crates/objc2-foundation/src/thread.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -40,8 +40,37 @@ pub fn is_multi_threaded() -> bool {

/// Whether the current thread is the main thread.
#[cfg(feature = "NSThread")]
#[inline]
pub fn is_main_thread() -> bool {
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Nit: Could you #[inline] this and the imp functions, so that they can be inlined even without LTO?

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And also, I'm doing merge commits in this repo, so if you could squash, that'd be nice!

NSThread::isMainThread_class()
#[cfg(not(feature = "gnustep-1-7"))]
#[inline(always)]
fn imp() -> bool {
// Normally you would use NSThread::isMainThread, but that function uses pthread_main_np under
// the hood. Benchmarks have shown that calling it directly is up to four times faster. So, we
// just use that instead.

#[cfg(feature = "libc")]
use libc::pthread_main_np;

#[link(name = "c", kind = "dylib")]
#[cfg(not(feature = "libc"))]
extern "C" {
// Avoid a dependency on `libc` if possible
fn pthread_main_np() -> std::os::raw::c_int;
}

// SAFETY: Does not affect thread safety if we're running in an actual macOS environment.
unsafe { pthread_main_np() != 0 }
}

#[cfg(feature = "gnustep-1-7")]
#[inline(always)]
fn imp() -> bool {
// Fall back to isMainThread on GNUStep, as pthread_main_np is not always available.
NSThread::isMainThread_class()
}

imp()
}

#[allow(unused)]
Expand Down Expand Up @@ -181,7 +210,7 @@ impl MainThreadMarker {
#[cfg(feature = "NSThread")]
#[inline]
pub fn new() -> Option<Self> {
if NSThread::isMainThread_class() {
if is_main_thread() {
// SAFETY: We just checked that we are running on the main thread.
Some(unsafe { Self::new_unchecked() })
} else {
Expand Down