Internalize strings in-place

src/x64/codegen-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.
 
 #include "src/x64/codegen-x64.h"
 
 #if V8_TARGET_ARCH_X64
 
 #include "src/codegen.h"
 #include "src/macro-assembler.h"
@@ skipping 59 matching lines @@
   // Fetch the instance type of the receiver into result register.
   __ movp(result, FieldOperand(string, HeapObject::kMapOffset));
   __ movzxbl(result, FieldOperand(result, Map::kInstanceTypeOffset));
 
   // We need special handling for indirect strings.
   Label check_sequential;
   __ testb(result, Immediate(kIsIndirectStringMask));
   __ j(zero, &check_sequential, Label::kNear);
 
   // Dispatch on the indirect string shape: slice or cons.
-  Label cons_string;
-  __ testb(result, Immediate(kSlicedNotConsMask));
-  __ j(zero, &cons_string, Label::kNear);
+  Label cons_string, thin_string;
+  __ andl(result, Immediate(kStringRepresentationMask));
+  __ cmpl(result, Immediate(kConsStringTag));
+  __ j(equal, &cons_string, Label::kNear);
+  __ cmpl(result, Immediate(kThinStringTag));
+  __ j(equal, &thin_string, Label::kNear);
 
   // Handle slices.
   Label indirect_string_loaded;
   __ SmiToInteger32(result, FieldOperand(string, SlicedString::kOffsetOffset));
   __ addp(index, result);
   __ movp(string, FieldOperand(string, SlicedString::kParentOffset));
   __ jmp(&indirect_string_loaded, Label::kNear);
 
+  // Handle thin strings.
+  __ bind(&thin_string);
+  __ movp(string, FieldOperand(string, ThinString::kActualOffset));
+  __ jmp(&indirect_string_loaded, Label::kNear);
+
   // Handle cons strings.
   // Check whether the right hand side is the empty string (i.e. if
   // this is really a flat string in a cons string). If that is not
   // the case we would rather go to the runtime system now to flatten
   // the string.
   __ bind(&cons_string);
   __ CompareRoot(FieldOperand(string, ConsString::kSecondOffset),
                  Heap::kempty_stringRootIndex);
   __ j(not_equal, call_runtime);
   __ movp(string, FieldOperand(string, ConsString::kFirstOffset));
@@ skipping 138 matching lines @@
     return Operand(base_reg_, argument_count_reg_, times_pointer_size,
         displacement_to_last_argument + (receiver - 1 - index) * kPointerSize);
   }
 }
 
 
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_TARGET_ARCH_X64