[PATCH] score: RTEMS_PREDICT_TRUE(), RTEMS_PREDICT_FALSE()
Sebastian Huber
sebastian.huber at embedded-brains.de
Tue Jul 24 07:03:51 UTC 2018
Add RTEMS_PREDICT_TRUE() and RTEMS_PREDICT_FALSE() for static branch
prediction hints.
Close #3475.
---
cpukit/include/rtems/score/basedefs.h | 28 ++++++++++++++++++++++++++++
cpukit/posix/src/sempost.c | 4 ++--
cpukit/posix/src/semtimedwait.c | 2 +-
cpukit/posix/src/semtrywait.c | 2 +-
cpukit/score/src/condition.c | 4 +++-
cpukit/score/src/futex.c | 2 +-
cpukit/score/src/mutex.c | 16 ++++++++--------
cpukit/score/src/semaphore.c | 10 +++++-----
testsuites/sptests/spmisc01/init.c | 25 +++++++++++++++++++++++++
9 files changed, 74 insertions(+), 19 deletions(-)
diff --git a/cpukit/include/rtems/score/basedefs.h b/cpukit/include/rtems/score/basedefs.h
index 8169f6db8c..7a52de895d 100644
--- a/cpukit/include/rtems/score/basedefs.h
+++ b/cpukit/include/rtems/score/basedefs.h
@@ -281,6 +281,34 @@
#define RTEMS_DEFINE_GLOBAL_SYMBOL( _name, _value )
#endif
+/**
+ * @brief Returns the value of the specified integral expressen and tells the
+ * compiler that the predicted value is true (1).
+ *
+ * @param[in] _exp The expression.
+ *
+ * @return The value of the expression.
+ */
+#if defined(__GNUC__)
+ #define RTEMS_PREDICT_TRUE( _exp ) __builtin_expect( ( _exp ), 1 )
+#else
+ #define RTEMS_PREDICT_TRUE( _exp ) ( _exp )
+#endif
+
+/**
+ * @brief Returns the value of the specified integral expressen and tells the
+ * compiler that the predicted value is false (0).
+ *
+ * @param[in] _exp The expression.
+ *
+ * @return The value of the expression.
+ */
+#if defined(__GNUC__)
+ #define RTEMS_PREDICT_FALSE( _exp ) __builtin_expect( ( _exp ), 0 )
+#else
+ #define RTEMS_PREDICT_FALSE( _exp ) ( _exp )
+#endif
+
#if __cplusplus >= 201103L
#define RTEMS_STATIC_ASSERT(cond, msg) \
static_assert(cond, # msg)
diff --git a/cpukit/posix/src/sempost.c b/cpukit/posix/src/sempost.c
index de0ae71fc7..d750c1178c 100644
--- a/cpukit/posix/src/sempost.c
+++ b/cpukit/posix/src/sempost.c
@@ -40,13 +40,13 @@ int sem_post( sem_t *_sem )
heads = sem->Queue.Queue.heads;
count = sem->count;
- if ( __predict_true( heads == NULL && count < SEM_VALUE_MAX ) ) {
+ if ( RTEMS_PREDICT_TRUE( heads == NULL && count < SEM_VALUE_MAX ) ) {
sem->count = count + 1;
_Sem_Queue_release( sem, level, &queue_context );
return 0;
}
- if ( __predict_true( heads != NULL ) ) {
+ if ( RTEMS_PREDICT_TRUE( heads != NULL ) ) {
const Thread_queue_Operations *operations;
Thread_Control *first;
diff --git a/cpukit/posix/src/semtimedwait.c b/cpukit/posix/src/semtimedwait.c
index 9e7bb466dd..16d0c24c9f 100644
--- a/cpukit/posix/src/semtimedwait.c
+++ b/cpukit/posix/src/semtimedwait.c
@@ -46,7 +46,7 @@ int sem_timedwait(
executing = _Sem_Queue_acquire_critical( sem, &queue_context );
count = sem->count;
- if ( __predict_true( count > 0 ) ) {
+ if ( RTEMS_PREDICT_TRUE( count > 0 ) ) {
sem->count = count - 1;
_Sem_Queue_release( sem, level, &queue_context );
return 0;
diff --git a/cpukit/posix/src/semtrywait.c b/cpukit/posix/src/semtrywait.c
index 673343d4b4..759744ec8e 100644
--- a/cpukit/posix/src/semtrywait.c
+++ b/cpukit/posix/src/semtrywait.c
@@ -35,7 +35,7 @@ int sem_trywait( sem_t *_sem )
_Sem_Queue_acquire_critical( sem, &queue_context );
count = sem->count;
- if ( __predict_true( count > 0 ) ) {
+ if ( RTEMS_PREDICT_TRUE( count > 0 ) ) {
sem->count = count - 1;
_Sem_Queue_release( sem, level, &queue_context );
return 0;
diff --git a/cpukit/score/src/condition.c b/cpukit/score/src/condition.c
index 9913d86d34..892245baf5 100644
--- a/cpukit/score/src/condition.c
+++ b/cpukit/score/src/condition.c
@@ -279,7 +279,9 @@ static void _Condition_Wake( struct _Condition_Control *_condition, int count )
* In common uses cases of condition variables there are normally no threads
* on the queue, so check this condition early.
*/
- if ( __predict_true( _Thread_queue_Is_empty( &condition->Queue.Queue ) ) ) {
+ if (
+ RTEMS_PREDICT_TRUE( _Thread_queue_Is_empty( &condition->Queue.Queue ) )
+ ) {
_Condition_Queue_release( condition, &context.Base );
return;
}
diff --git a/cpukit/score/src/futex.c b/cpukit/score/src/futex.c
index 6487882819..f32a13c449 100644
--- a/cpukit/score/src/futex.c
+++ b/cpukit/score/src/futex.c
@@ -151,7 +151,7 @@ int _Futex_Wake( struct _Futex_Control *_futex, int count )
* called in the fast path. Normally there are no threads on the queue, so
* check this condition early.
*/
- if ( __predict_true( _Thread_queue_Is_empty( &futex->Queue.Queue ) ) ) {
+ if ( RTEMS_PREDICT_TRUE( _Thread_queue_Is_empty( &futex->Queue.Queue ) ) ) {
_Futex_Queue_release( futex, level, &context.Base );
return 0;
}
diff --git a/cpukit/score/src/mutex.c b/cpukit/score/src/mutex.c
index e2f5bb52fc..8cc47f28bb 100644
--- a/cpukit/score/src/mutex.c
+++ b/cpukit/score/src/mutex.c
@@ -128,7 +128,7 @@ static void _Mutex_Release_critical(
mutex->Queue.Queue.owner = NULL;
_Thread_Resource_count_decrement( executing );
- if ( __predict_true( heads == NULL ) ) {
+ if ( RTEMS_PREDICT_TRUE( heads == NULL ) ) {
_Mutex_Queue_release( mutex, level, queue_context );
} else {
_Thread_queue_Context_set_ISR_level( queue_context, level );
@@ -157,7 +157,7 @@ void _Mutex_Acquire( struct _Mutex_Control *_mutex )
owner = mutex->Queue.Queue.owner;
- if ( __predict_true( owner == NULL ) ) {
+ if ( RTEMS_PREDICT_TRUE( owner == NULL ) ) {
mutex->Queue.Queue.owner = executing;
_Thread_Resource_count_increment( executing );
_Mutex_Queue_release( mutex, level, &queue_context );
@@ -185,7 +185,7 @@ int _Mutex_Acquire_timed(
owner = mutex->Queue.Queue.owner;
- if ( __predict_true( owner == NULL ) ) {
+ if ( RTEMS_PREDICT_TRUE( owner == NULL ) ) {
mutex->Queue.Queue.owner = executing;
_Thread_Resource_count_increment( executing );
_Mutex_Queue_release( mutex, level, &queue_context );
@@ -218,7 +218,7 @@ int _Mutex_Try_acquire( struct _Mutex_Control *_mutex )
owner = mutex->Queue.Queue.owner;
- if ( __predict_true( owner == NULL ) ) {
+ if ( RTEMS_PREDICT_TRUE( owner == NULL ) ) {
mutex->Queue.Queue.owner = executing;
_Thread_Resource_count_increment( executing );
eno = 0;
@@ -270,7 +270,7 @@ void _Mutex_recursive_Acquire( struct _Mutex_recursive_Control *_mutex )
owner = mutex->Mutex.Queue.Queue.owner;
- if ( __predict_true( owner == NULL ) ) {
+ if ( RTEMS_PREDICT_TRUE( owner == NULL ) ) {
mutex->Mutex.Queue.Queue.owner = executing;
_Thread_Resource_count_increment( executing );
_Mutex_Queue_release( &mutex->Mutex, level, &queue_context );
@@ -301,7 +301,7 @@ int _Mutex_recursive_Acquire_timed(
owner = mutex->Mutex.Queue.Queue.owner;
- if ( __predict_true( owner == NULL ) ) {
+ if ( RTEMS_PREDICT_TRUE( owner == NULL ) ) {
mutex->Mutex.Queue.Queue.owner = executing;
_Thread_Resource_count_increment( executing );
_Mutex_Queue_release( &mutex->Mutex, level, &queue_context );
@@ -339,7 +339,7 @@ int _Mutex_recursive_Try_acquire( struct _Mutex_recursive_Control *_mutex )
owner = mutex->Mutex.Queue.Queue.owner;
- if ( __predict_true( owner == NULL ) ) {
+ if ( RTEMS_PREDICT_TRUE( owner == NULL ) ) {
mutex->Mutex.Queue.Queue.owner = executing;
_Thread_Resource_count_increment( executing );
eno = 0;
@@ -372,7 +372,7 @@ void _Mutex_recursive_Release( struct _Mutex_recursive_Control *_mutex )
nest_level = mutex->nest_level;
- if ( __predict_true( nest_level == 0 ) ) {
+ if ( RTEMS_PREDICT_TRUE( nest_level == 0 ) ) {
_Mutex_Release_critical( &mutex->Mutex, executing, level, &queue_context );
} else {
mutex->nest_level = nest_level - 1;
diff --git a/cpukit/score/src/semaphore.c b/cpukit/score/src/semaphore.c
index f76ee332a4..f9b8b48fe1 100644
--- a/cpukit/score/src/semaphore.c
+++ b/cpukit/score/src/semaphore.c
@@ -53,7 +53,7 @@ void _Semaphore_Wait( struct _Semaphore_Control *_sem )
executing = _Sem_Queue_acquire_critical( sem, &queue_context );
count = sem->count;
- if ( __predict_true( count > 0 ) ) {
+ if ( RTEMS_PREDICT_TRUE( count > 0 ) ) {
sem->count = count - 1;
_Sem_Queue_release( sem, level, &queue_context );
} else {
@@ -86,7 +86,7 @@ int _Semaphore_Wait_timed_ticks( struct _Semaphore_Control *_sem, uint32_t ticks
executing = _Sem_Queue_acquire_critical( sem, &queue_context );
count = sem->count;
- if ( __predict_true( count > 0 ) ) {
+ if ( RTEMS_PREDICT_TRUE( count > 0 ) ) {
sem->count = count - 1;
_Sem_Queue_release( sem, level, &queue_context );
return 0;
@@ -121,7 +121,7 @@ int _Semaphore_Try_wait( struct _Semaphore_Control *_sem )
_Sem_Queue_acquire_critical( sem, &queue_context );
count = sem->count;
- if ( __predict_true( count > 0 ) ) {
+ if ( RTEMS_PREDICT_TRUE( count > 0 ) ) {
sem->count = count - 1;
eno = 0;
} else {
@@ -145,7 +145,7 @@ void _Semaphore_Post( struct _Semaphore_Control *_sem )
_Sem_Queue_acquire_critical( sem, &queue_context );
heads = sem->Queue.Queue.heads;
- if ( __predict_true( heads == NULL ) ) {
+ if ( RTEMS_PREDICT_TRUE( heads == NULL ) ) {
++sem->count;
_Sem_Queue_release( sem, level, &queue_context );
} else {
@@ -178,7 +178,7 @@ void _Semaphore_Post_binary( struct _Semaphore_Control *_sem )
_Sem_Queue_acquire_critical( sem, &queue_context );
heads = sem->Queue.Queue.heads;
- if ( __predict_true( heads == NULL ) ) {
+ if ( RTEMS_PREDICT_TRUE( heads == NULL ) ) {
sem->count = 1;
_Sem_Queue_release( sem, level, &queue_context );
} else {
diff --git a/testsuites/sptests/spmisc01/init.c b/testsuites/sptests/spmisc01/init.c
index 4fab3f0e84..c406cd07aa 100644
--- a/testsuites/sptests/spmisc01/init.c
+++ b/testsuites/sptests/spmisc01/init.c
@@ -229,6 +229,31 @@ static void Init(rtems_task_argument arg)
rtems_test_assert(RTEMS_XCONCAT(CON, CAT)() == 91);
rtems_test_assert(strcmp(RTEMS_STRING(str), "str") == 0);
rtems_test_assert(strcmp(RTEMS_XSTRING(STR), "ing") == 0);
+
+ if (RTEMS_PREDICT_TRUE(true)) {
+ rtems_test_assert(true);
+ } else {
+ rtems_test_assert(false);
+ }
+
+ if (RTEMS_PREDICT_FALSE(true)) {
+ rtems_test_assert(true);
+ } else {
+ rtems_test_assert(false);
+ }
+
+ if (RTEMS_PREDICT_TRUE(false)) {
+ rtems_test_assert(false);
+ } else {
+ rtems_test_assert(true);
+ }
+
+ if (RTEMS_PREDICT_FALSE(false)) {
+ rtems_test_assert(false);
+ } else {
+ rtems_test_assert(true);
+ }
+
TEST_END();
rtems_test_exit(0);
}
--
2.13.7
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