Fast TLS support on mac.

src/platform-tls-mac.h

+// Copyright 2011 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
+//       with the distribution.
+//     * Neither the name of Google Inc. nor the names of its
+//       contributors may be used to endorse or promote products derived
+//       from this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+#ifndef V8_PLATFORM_TLS_MAC_H_
+#define V8_PLATFORM_TLS_MAC_H_
+
+#include "globals.h"
+
+namespace v8 {
+namespace internal {
+
+#if defined(V8_HOST_ARCH_IA32) || defined(V8_HOST_ARCH_X64)
+
+#define V8_FAST_TLS_SUPPORTED 1
+
+INLINE(intptr_t InternalGetExistingThreadLocal(intptr_t index));
+
+inline intptr_t InternalGetExistingThreadLocal(intptr_t index) {
+  // The constants below are taken from pthreads.s from the XNU kernel
+  // sources archive at www.opensource.apple.com.
+  intptr_t result;
+#if defined(V8_HOST_ARCH_IA32)
+  asm("movl %%gs:0x48(,%1,4), %0;"
+      :"=r"(result)  // Output must be a writable register.
+      :"0"(index));  // Input is the same as output.
+#else
+  asm("movq %%gs:0x60(,%1,8), %0;"
+      :"=r"(result)
+      :"0"(index));
+#endif
+  return result;
+}
+
+#endif
+
+} }  // namespace v8::internal
+
+#endif  // V8_PLATFORM_TLS_MAC_H_