Fix performance regressions due to lazy initialization.

src/platform-posix.cc

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@@ skipping 116 matching lines @@
 }
 
 
 #define UNARY_MATH_FUNCTION(name, generator)             \
 static UnaryMathFunction fast_##name##_function = NULL;  \
 V8_DECLARE_ONCE(fast_##name##_init_once);                \
 void init_fast_##name##_function() {                     \
   fast_##name##_function = generator;                    \
 }                                                        \
 double fast_##name(double x) {                           \
-  CallOnce(&fast_##name##_init_once,                     \
-           &init_fast_##name##_function);                \
+  if (!fast_##name##_function) {                         \

[danno, 2012/03/29 07:45:17]

Since this is also could be called frequently, perhaps it makes sense to
initialize the function list from InitializeOncePerProcess?

[Philippe, 2012/03/29 09:00:48]

I tried to do that initially by calling these initialization functions once in
OS::SetUp(). The problem is that the functions used to create these math
functions (during OS SetUp) depend on CpuFeatures initialized by CPU::SetUp().
CPU itself depends on some OS functions that require initialization (which is
why in InitializeOncePerProcess(), OS is initialized before CPU). What we can do
though, is adding a function like OS::PostSetUp() for example which would be
called after CPU initialization. This function could initialize the math
functions.

What do you think?

[danno, 2012/03/29 09:07:20]

Calling it from OS::PostSetUp seems fine. I would definitely prefer that to the
lazy initialized version.

On 2012/03/29 09:00:48, Philippe wrote:

[Philippe, 2012/03/29 09:26:53]

Done.

+    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