Remove static Mutex from math function intializers.

src/platform-posix.cc

 // Copyright 2011 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 109 matching lines @@
 
 
 // ----------------------------------------------------------------------------
 // Math functions
 
 double modulo(double x, double y) {
   return fmod(x, 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);                   \
 }
 
 UNARY_MATH_FUNCTION(sin, CreateTranscendentalFunction(TranscendentalCache::SIN))
 UNARY_MATH_FUNCTION(cos, CreateTranscendentalFunction(TranscendentalCache::COS))
 UNARY_MATH_FUNCTION(tan, CreateTranscendentalFunction(TranscendentalCache::TAN))
 UNARY_MATH_FUNCTION(log, CreateTranscendentalFunction(TranscendentalCache::LOG))
 UNARY_MATH_FUNCTION(sqrt, CreateSqrtFunction())
 
 #undef MATH_FUNCTION
@@ skipping 364 matching lines @@
   return ntohl(value);
 }
 
 
 Socket* OS::CreateSocket() {
   return new POSIXSocket();
 }
 
 
 } }  // namespace v8::internal