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| author | Thomas Rodgers <trodgers@redhat.com> | 2022-07-05 17:42:42 -0700 |
|---|---|---|
| committer | Thomas Rodgers <trodgers@redhat.com> | 2022-07-26 14:55:36 -0700 |
| commit | e75da2ace6b6f634237259ef62cfb2d3d34adb10 (patch) | |
| tree | 080207538b29a0db6b02397811a3a7b0d9424e60 | |
| parent | db613e8fa841259f74740665ee9e508bd73ea1c4 (diff) | |
| download | gcc-e75da2ace6b6f634237259ef62cfb2d3d34adb10.zip gcc-e75da2ace6b6f634237259ef62cfb2d3d34adb10.tar.gz gcc-e75da2ace6b6f634237259ef62cfb2d3d34adb10.tar.bz2 | |
libstdc++: Minor codegen improvement for atomic wait spinloop
This patch merges the spin loops in the atomic wait implementation which is a
minor codegen improvement.
libstdc++-v3/ChangeLog:
* include/bits/atomic_wait.h (__atomic_spin): Merge spin loops.
| -rw-r--r-- | libstdc++-v3/include/bits/atomic_wait.h | 17 |
1 files changed, 7 insertions, 10 deletions
diff --git a/libstdc++-v3/include/bits/atomic_wait.h b/libstdc++-v3/include/bits/atomic_wait.h index 125b1ca..a6d55d3 100644 --- a/libstdc++-v3/include/bits/atomic_wait.h +++ b/libstdc++-v3/include/bits/atomic_wait.h @@ -142,8 +142,8 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION #endif } - constexpr auto __atomic_spin_count_1 = 12; - constexpr auto __atomic_spin_count_2 = 4; + constexpr auto __atomic_spin_count_relax = 12; + constexpr auto __atomic_spin_count = 16; struct __default_spin_policy { @@ -157,18 +157,15 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION bool __atomic_spin(_Pred& __pred, _Spin __spin = _Spin{ }) noexcept { - for (auto __i = 0; __i < __atomic_spin_count_1; ++__i) + for (auto __i = 0; __i < __atomic_spin_count; ++__i) { if (__pred()) return true; - __detail::__thread_relax(); - } - for (auto __i = 0; __i < __atomic_spin_count_2; ++__i) - { - if (__pred()) - return true; - __detail::__thread_yield(); + if (__i < __atomic_spin_count_relax) + __detail::__thread_relax(); + else + __detail::__thread_yield(); } while (__spin()) |