Fix performance regressions due to lazy initialization.

src/assembler.cc

 // Copyright (c) 1994-2006 Sun Microsystems Inc.
 // 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.
 //
@@ skipping 94 matching lines @@
     double_constants->one_half = 0.5;
     double_constants->minus_zero = -0.0;
     double_constants->uint8_max_value = 255;
     double_constants->zero = 0.0;
     double_constants->canonical_non_hole_nan = OS::nan_value();
     double_constants->the_hole_nan = BitCast<double>(kHoleNanInt64);
     double_constants->negative_infinity = -V8_INFINITY;
   }
 };
 
-static LazyInstance<DoubleConstant, InitializeDoubleConstants>::type
-    double_constants = LAZY_INSTANCE_INITIALIZER;
+static LazyInstance<DoubleConstant, InitializeDoubleConstants,
+    SingleThreadInitOnceTrait>::type double_constants =
+        LAZY_INSTANCE_INITIALIZER;
 
 const char* const RelocInfo::kFillerCommentString = "DEOPTIMIZATION PADDING";
 
 // -----------------------------------------------------------------------------
 // Implementation of AssemblerBase
 
 AssemblerBase::AssemblerBase(Isolate* isolate)
     : isolate_(isolate),
       jit_cookie_(0) {
   if (FLAG_mask_constants_with_cookie && isolate != NULL)  {
@@ skipping 1171 matching lines @@
     assembler_->RecordRelocInfo(RelocInfo::POSITION, state_.current_position);
     state_.written_position = state_.current_position;
     written = true;
   }
 
   // Return whether something was written.
   return written;
 }
 
 } }  // namespace v8::internal