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[llvm][Support] Use thread_local caching for llvm::get_threadid() query on Apple systems (#87219)

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I was profiling our compiler and noticed that `llvm::get_threadid` was
at the top of the hotlist, taking up a surprising 5% (7 seconds) in the
profile trace. It seems that computing this on MacOS systems is
non-trivial, so cache the result in a thread_local.

Co-authored-by: Mehdi Amini <joker.eph@gmail.com>
This commit is contained in:
Jeff Niu 2024-04-01 13:59:53 -07:00 committed by GitHub
parent b8cc3ba409
commit f2f01f6b03
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1 changed files with 5 additions and 2 deletions
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7
llvm/lib/Support/Unix/Threading.inc
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@ -115,8 +115,11 @@ uint64_t llvm::get_threadid() {
// Calling "mach_thread_self()" bumps the reference count on the thread
// port, so we need to deallocate it. mach_task_self() doesn't bump the ref
// count.
thread_port_t Self = mach_thread_self();
mach_port_deallocate(mach_task_self(), Self);
static thread_local thread_port_t Self = [] {
thread_port_t InitSelf = mach_thread_self();
mach_port_deallocate(mach_task_self(), Self);
return InitSelf;
}();
return Self;
#elif defined(__FreeBSD__)
return uint64_t(pthread_getthreadid_np());