Revert of Internalize strings in-place

src/x64/macro-assembler-x64.cc

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #if V8_TARGET_ARCH_X64
 
 #include "src/base/bits.h"
 #include "src/base/division-by-constant.h"
 #include "src/bootstrapper.h"
 #include "src/codegen.h"
@@ skipping 2522 matching lines @@
   // Check that both are flat one-byte strings.
   DCHECK(kNotStringTag != 0);
   const int kFlatOneByteStringMask =
       kIsNotStringMask | kStringRepresentationMask | kStringEncodingMask;
   const int kFlatOneByteStringTag =
       kStringTag | kOneByteStringTag | kSeqStringTag;
 
   andl(scratch1, Immediate(kFlatOneByteStringMask));
   andl(scratch2, Immediate(kFlatOneByteStringMask));
   // Interleave the bits to check both scratch1 and scratch2 in one test.
-  const int kShift = 8;
-  DCHECK_EQ(0, kFlatOneByteStringMask & (kFlatOneByteStringMask << kShift));
-  shlp(scratch2, Immediate(kShift));
-  orp(scratch1, scratch2);
+  DCHECK_EQ(0, kFlatOneByteStringMask & (kFlatOneByteStringMask << 3));
+  leap(scratch1, Operand(scratch1, scratch2, times_8, 0));
   cmpl(scratch1,
-       Immediate(kFlatOneByteStringTag + (kFlatOneByteStringTag << kShift)));
+       Immediate(kFlatOneByteStringTag + (kFlatOneByteStringTag << 3)));
   j(not_equal, on_fail, near_jump);
 }
 
 void MacroAssembler::JumpIfBothInstanceTypesAreNotSequentialOneByte(
     Register first_object_instance_type, Register second_object_instance_type,
     Register scratch1, Register scratch2, Label* on_fail,
     Label::Distance near_jump) {
   // Load instance type for both strings.
   movp(scratch1, first_object_instance_type);
   movp(scratch2, second_object_instance_type);
@@ skipping 2740 matching lines @@
   movl(rax, dividend);
   shrl(rax, Immediate(31));
   addl(rdx, rax);
 }
 
 
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_TARGET_ARCH_X64