X64 Crankshaft: Revert r7071 and fix DoStoreContextSlot in a different way.

src/x64/macro-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 77 matching lines @@
   cmpq(with, kScratchRegister);
 }
 
 
 void MacroAssembler::RecordWriteHelper(Register object,
                                        Register addr,
                                        Register scratch) {
   if (FLAG_debug_code) {
     // Check that the object is not in new space.
     NearLabel not_in_new_space;
-    if (addr.is(kScratchRegister)) {
-      push(kScratchRegister);
-      InNewSpace(object, scratch, not_equal, &not_in_new_space);
-      pop(kScratchRegister);
-    } else {
-      InNewSpace(object, scratch, not_equal, &not_in_new_space);
-    }
+    InNewSpace(object, scratch, not_equal, &not_in_new_space);
     Abort("new-space object passed to RecordWriteHelper");
     bind(&not_in_new_space);
   }
 
   // Compute the page start address from the heap object pointer, and reuse
   // the 'object' register for it.
   and_(object, Immediate(~Page::kPageAlignmentMask));
 
   // Compute number of region covering addr. See Page::GetRegionNumberForAddress
   // method for more details.
@@ skipping 2555 matching lines @@
   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
 
 #endif  // V8_TARGET_ARCH_X64