Fix the GC branch so it compiles and runs on 64 bit.

src/x64/assembler-x64.cc

 // 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
@@ skipping 29 matching lines @@
 
 
 #ifdef DEBUG
 bool CpuFeatures::initialized_ = false;
 #endif
 uint64_t CpuFeatures::supported_ = CpuFeatures::kDefaultCpuFeatures;
 uint64_t CpuFeatures::found_by_runtime_probing_ = 0;
 
 
 void CpuFeatures::Probe() {
-  ASSERT(!initialized_);
+  ASSERT(supported_ == CpuFeatures::kDefaultCpuFeatures);
 #ifdef DEBUG
   initialized_ = true;
 #endif
   supported_ = kDefaultCpuFeatures;
   if (Serializer::enabled()) {
     supported_ |= OS::CpuFeaturesImpliedByPlatform();
     return;  // No features if we might serialize.
   }
 
   const int kBufferSize = 4 * KB;
@@ skipping 2973 matching lines @@
   // specially coded on x64 means that it is a relative 32 bit address, as used
   // by branch instructions.
   return (1 << rmode_) & kApplyMask;
 }
 
 
 
 } }  // namespace v8::internal
 
 #endif  // V8_TARGET_ARCH_X64