manually "shrink wrap" fast path in pthread_once

this change is a workaround for the inability of current compilers to
perform "shrink wrapping" optimizations. in casual testing, it roughly
doubled the performance of pthread_once when called on an
already-finished once control object.

diff --git a/src/thread/pthread_once.c b/src/thread/pthread_once.c
index 7c47385..df655ef 100644 (file)
--- a/src/thread/pthread_once.c
+++ b/src/thread/pthread_once.c
@@ -8,15 +8,8 @@ static void undo(void *control)
                __wake(control, -1, 1);
 }
 
-int __pthread_once(pthread_once_t *control, void (*init)(void))
+int __pthread_once_full(pthread_once_t *control, void (*init)(void))
 {
-       /* Return immediately if init finished before, but ensure that
-        * effects of the init routine are visible to the caller. */
-       if (*control == 2) {
-               a_barrier();
-               return 0;
-       }
-
        /* Try to enter initializing state. Four possibilities:
         *  0 - we're the first or the other cancelled; run init
         *  1 - another thread is running init; wait
@@ -43,4 +36,15 @@ int __pthread_once(pthread_once_t *control, void (*init)(void))
        }
 }
 
+int __pthread_once(pthread_once_t *control, void (*init)(void))
+{
+       /* Return immediately if init finished before, but ensure that
+        * effects of the init routine are visible to the caller. */
+       if (*control == 2) {
+               a_barrier();
+               return 0;
+       }
+       return __pthread_once_full(control, init);
+}
+
 weak_alias(__pthread_once, pthread_once);