OS::MemMove/OS::MemCopy: Don't call through to generated code when size == 0 to avoid prefetching i…

src/platform-win32.cc

 // Copyright 2012 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 142 matching lines @@
 }
 
 // Initialize to library version so we can call this at any time during startup.
 static OS::MemMoveFunction memmove_function = &MemMoveWrapper;
 
 // Defined in codegen-ia32.cc.
 OS::MemMoveFunction CreateMemMoveFunction();
 
 // Copy memory area to disjoint memory area.
 void OS::MemMove(void* dest, const void* src, size_t size) {
+  if (size == 0) return;
   // Note: here we rely on dependent reads being ordered. This is true
   // on all architectures we currently support.
   (*memmove_function)(dest, src, size);
 }
 
 #endif  // V8_TARGET_ARCH_IA32
 
 #ifdef _WIN64
 typedef double (*ModuloFunction)(double, double);
 static ModuloFunction modulo_function = NULL;
@@ skipping 1813 matching lines @@
   limit_mutex = CreateMutex();
 }
 
 
 void OS::TearDown() {
   delete limit_mutex;
 }
 
 
 } }  // namespace v8::internal