Fix performance regressions due to lazy initialization.

src/platform-posix.cc

Index: src/platform-posix.cc
diff --git a/src/platform-posix.cc b/src/platform-posix.cc
index a729b662605ad1377395cf7f0fb9668d3863ce48..750b9117d96c79bd8742b224da9fadf6cc6e6ba3 100644
--- a/src/platform-posix.cc
+++ b/src/platform-posix.cc
@@ -134,8 +134,10 @@ 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);                   \
 }