X64: Fix bug that reads from rax instead of correct register.

src/x64/macro-assembler-x64.cc

 // Copyright 2009 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 2400 matching lines @@
   LoadRoot(kScratchRegister, Heap::kConsAsciiStringMapRootIndex);
   movq(FieldOperand(result, HeapObject::kMapOffset), kScratchRegister);
 }
 
 
 void MacroAssembler::LoadContext(Register dst, int context_chain_length) {
   if (context_chain_length > 0) {
     // Move up the chain of contexts to the context containing the slot.
     movq(dst, Operand(rsi, Context::SlotOffset(Context::CLOSURE_INDEX)));
     // Load the function context (which is the incoming, outer context).
-    movq(rax, FieldOperand(rax, JSFunction::kContextOffset));
+    movq(dst, FieldOperand(dst, JSFunction::kContextOffset));
     for (int i = 1; i < context_chain_length; i++) {
       movq(dst, Operand(dst, Context::SlotOffset(Context::CLOSURE_INDEX)));
       movq(dst, FieldOperand(dst, JSFunction::kContextOffset));
     }
     // The context may be an intermediate context, not a function context.
     movq(dst, Operand(dst, Context::SlotOffset(Context::FCONTEXT_INDEX)));
   } else {  // context is the current function context.
     // The context may be an intermediate context, not a function context.
     movq(dst, Operand(rsi, Context::SlotOffset(Context::FCONTEXT_INDEX)));
   }
@@ skipping 12 matching lines @@
 CodePatcher::~CodePatcher() {
   // Indicate that code has changed.
   CPU::FlushICache(address_, size_);
 
   // Check that the code was patched as expected.
   ASSERT(masm_.pc_ == address_ + size_);
   ASSERT(masm_.reloc_info_writer.pos() == address_ + size_ + Assembler::kGap);
 }
 
 } }  // namespace v8::internal