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[compiler-rt][builtins] Add opt-in pthread_mutex_t locks to libatomic #95326

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Merged
merged 1 commit into from
Jun 13, 2024
+20 −2
Merged

[compiler-rt][builtins] Add opt-in pthread_mutex_t locks to libatomic #95326

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8 changes: 8 additions & 0 deletions compiler-rt/lib/builtins/CMakeLists.txt
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Original file line number Diff line number Diff line change
Expand Up @@ -237,6 +237,14 @@ if(NOT FUCHSIA AND NOT COMPILER_RT_BAREMETAL_BUILD)
)
endif()

option(COMPILER_RT_LIBATOMIC_USE_PTHREAD
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Perhaps this can be the default for Linux if not Android.

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We can try to switch that after this PR lands.

"Whether libatomic should use pthreads if available."
Off)

if(COMPILER_RT_LIBATOMIC_USE_PTHREAD)
add_compile_definitions(_LIBATOMIC_USE_PTHREAD)
endif()

if(COMPILER_RT_HAS_ATOMIC_KEYWORD AND NOT COMPILER_RT_EXCLUDE_ATOMIC_BUILTIN)
set(GENERIC_SOURCES
${GENERIC_SOURCES}
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14 changes: 12 additions & 2 deletions compiler-rt/lib/builtins/atomic.c
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Expand Up @@ -12,7 +12,7 @@
//
// 1) This code must work with C programs that do not link to anything
// (including pthreads) and so it should not depend on any pthread
// functions.
// functions. If the user wishes to opt into using pthreads, they may do so.
// 2) Atomic operations, rather than explicit mutexes, are most commonly used
// on code where contended operations are rate.
//
Expand Down Expand Up @@ -56,7 +56,17 @@ static const long SPINLOCK_MASK = SPINLOCK_COUNT - 1;
// defined. Each platform should define the Lock type, and corresponding
// lock() and unlock() functions.
////////////////////////////////////////////////////////////////////////////////
#if defined(__FreeBSD__) || defined(__DragonFly__)
#if defined(_LIBATOMIC_USE_PTHREAD)
#include <pthread.h>
typedef pthread_mutex_t Lock;
/// Unlock a lock. This is a release operation.
__inline static void unlock(Lock *l) { pthread_mutex_unlock(l); }
/// Locks a lock.
__inline static void lock(Lock *l) { pthread_mutex_lock(l); }
/// locks for atomic operations
static Lock locks[SPINLOCK_COUNT];

#elif defined(__FreeBSD__) || defined(__DragonFly__)
#include <errno.h>
// clang-format off
#include <sys/types.h>
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