Allocate the right number of fast context slots on X64. Ported from ia32....

src/x64/codegen-x64.cc

 // Copyright 2010 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 342 matching lines @@
     // rsi: callee's context
     allocator_->Initialize();
 
     if (info->mode() == CompilationInfo::PRIMARY) {
       frame_->Enter();
 
       // Allocate space for locals and initialize them.
       frame_->AllocateStackSlots();
 
       // Allocate the local context if needed.
-      int heap_slots = scope()->num_heap_slots();
+      int heap_slots = scope()->num_heap_slots() - Context::MIN_CONTEXT_SLOTS;
       if (heap_slots > 0) {
         Comment cmnt(masm_, "[ allocate local context");
         // Allocate local context.
         // Get outer context and create a new context based on it.
         frame_->PushFunction();
         Result context;
         if (heap_slots <= FastNewContextStub::kMaximumSlots) {
           FastNewContextStub stub(heap_slots);
           context = frame_->CallStub(&stub, 1);
         } else {
@@ skipping 11083 matching lines @@
   // Call the function from C++.
   return FUNCTION_CAST<ModuloFunction>(buffer);
 }
 
 #endif
 
 
 #undef __
 
 } }  // namespace v8::internal