Fix performance regressions due to lazy initialization.

src/platform-macos.cc

Index: src/platform-macos.cc
diff --git a/src/platform-macos.cc b/src/platform-macos.cc
index bfcaab0b51f13f7f1ce9ad1410c855c724a5f4db..52a4a3658f472e8d5d569d1e9c1aa8d3ffe72aed 100644
--- a/src/platform-macos.cc
+++ b/src/platform-macos.cc
@@ -101,6 +101,15 @@ void OS::SetUp() {
 }
 
 
+void MathSetup();  // Defined in platform-posix.cc.
+
+void OS::PostSetUp() {
+  // Math functions depend on CPU features therefore they are initialized after
+  // CPU.
+  MathSetup();
+}
+
+
 // We keep the lowest and highest addresses mapped as a quick way of
 // determining that pointers are outside the heap (used mostly in assertions
 // and verification).  The estimate is conservative, i.e., not all addresses in