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os: tweak LightEvent codegen

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This commit is contained in:
Michael Scire 2021-09-28 19:11:52 -07:00
parent 632b6b3330
commit c7634c66c4
1 changed files with 29 additions and 1 deletions
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30
libraries/libstratosphere/source/os/impl/os_internal_light_event_impl.os.horizon.hpp
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@ -72,8 +72,36 @@ namespace ams::os::impl {
return true;
}
ALWAYS_INLINE s32 LoadAcquireExclusiveForLightEvent(s32 *p) {
s32 v;
__asm__ __volatile__("ldaxr %w[v], %[p]" : [v]"=&r"(v) : [p]"Q"(*p) : "memory");
return v;
}
ALWAYS_INLINE bool StoreReleaseExclusiveForLightEvent(s32 *p, s32 v) {
int result;
__asm__ __volatile__("stlxr %w[result], %w[v], %[p]" : [result]"=&r"(result) : [v]"r"(v), [p]"Q"(*p) : "memory");
return result == 0;
}
ALWAYS_INLINE void ClearExclusiveForLightEvent() {
__asm__ __volatile__("clrex" ::: "memory");
}
ALWAYS_INLINE bool CompareAndSwap(std::atomic<s32> *state, s32 expected, s32 desired) {
return state->compare_exchange_strong(expected, desired);
/* NOTE: This works around gcc not emitting clrex on ldaxr fail. */
s32 * const state_ptr = reinterpret_cast<s32 *>(GetAddressOfAtomicInteger(state));
while (true) {
if (AMS_UNLIKELY(LoadAcquireExclusiveForLightEvent(state_ptr) != expected)) {
ClearExclusiveForLightEvent();
return false;
}
if (AMS_LIKELY(StoreReleaseExclusiveForLightEvent(state_ptr, desired))) {
return true;
}
}
}
}