Internalize strings in-place

src/arm/codegen-arm.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/arm/codegen-arm.h"
 
 #if V8_TARGET_ARCH_ARM
 
 #include <memory>
 
@@ skipping 314 matching lines @@
   // Fetch the instance type of the receiver into result register.
   __ ldr(result, FieldMemOperand(string, HeapObject::kMapOffset));
   __ ldrb(result, FieldMemOperand(result, Map::kInstanceTypeOffset));
 
   // We need special handling for indirect strings.
   Label check_sequential;
   __ tst(result, Operand(kIsIndirectStringMask));
   __ b(eq, &check_sequential);
 
   // Dispatch on the indirect string shape: slice or cons.
-  Label cons_string;
-  __ tst(result, Operand(kSlicedNotConsMask));
+  Label cons_string, thin_string;
+  __ and_(result, result, Operand(kStringRepresentationMask));
+  __ cmp(result, Operand(kConsStringTag));
   __ b(eq, &cons_string);
+  __ cmp(result, Operand(kThinStringTag));
+  __ b(eq, &thin_string);
 
   // Handle slices.
   Label indirect_string_loaded;
   __ ldr(result, FieldMemOperand(string, SlicedString::kOffsetOffset));
   __ ldr(string, FieldMemOperand(string, SlicedString::kParentOffset));
   __ add(index, index, Operand::SmiUntag(result));
   __ jmp(&indirect_string_loaded);
 
+  // Handle thin strings.
+  __ bind(&thin_string);
+  __ ldr(string, FieldMemOperand(string, ThinString::kActualOffset));
+  __ jmp(&indirect_string_loaded);
+
   // 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);
   __ ldr(result, FieldMemOperand(string, ConsString::kSecondOffset));
   __ CompareRoot(result, Heap::kempty_stringRootIndex);
   __ b(ne, call_runtime);
   // Get the first of the two strings and load its instance type.
@@ skipping 106 matching lines @@
     patcher.masm()->add(r0, pc, Operand(-8));
     patcher.masm()->ldr(pc, MemOperand(pc, -4));
     patcher.masm()->emit_code_stub_address(stub);
   }
 }
 
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_TARGET_ARCH_ARM