Remove static Mutex from math function intializers.

src/platform-posix.cc

Index: src/platform-posix.cc
diff --git a/src/platform-posix.cc b/src/platform-posix.cc
index 422180806a52ab4d547c45f4697cb126ec5a5e08..95edead8330b992a06803b1ff56bd0284528e9ae 100644
--- a/src/platform-posix.cc
+++ b/src/platform-posix.cc
@@ -127,17 +127,16 @@ double modulo(double x, double y) {
 }
 
 
-static Mutex* math_function_mutex = OS::CreateMutex();
-
 #define UNARY_MATH_FUNCTION(name, generator)             \
 static UnaryMathFunction fast_##name##_function = NULL;  \
+V8_DECLARE_ONCE(fast_##name##_init_once);                \
+void init_fast_##name##_function() {                     \

[fschneider, 2012/03/12 16:06:40]

I wonder if you can make this part of InitializeOncePerProcessImpl() in v8.cc to
make it slightly more efficient.

+  fast_##name##_function = generator;                    \
+  MemoryBarrier();                                       \

[fschneider, 2012/03/12 16:25:46]

You can remove this since CallOnce already has MemoryBarrier builtin.

+}                                                        \
 double fast_##name(double x) {                           \
-  if (fast_##name##_function == NULL) {                  \
-    ScopedLock lock(math_function_mutex);                \
-    UnaryMathFunction temp = generator;                  \
-    MemoryBarrier();                                     \
-    fast_##name##_function = temp;                       \
-  }                                                      \
+  CallOnce(&fast_##name##_init_once,                     \
+           &init_fast_##name##_function);                \
   return (*fast_##name##_function)(x);                   \
 }