Internalize strings in-place

src/x87/codegen-x87.cc

Index: src/x87/codegen-x87.cc
diff --git a/src/x87/codegen-x87.cc b/src/x87/codegen-x87.cc
index a2bba1dcd7c565c0544a8f6d6a3903fddefb1d06..92259350cbb6cb006fd1a2c6ba9ca9a03b013035 100644
--- a/src/x87/codegen-x87.cc
+++ b/src/x87/codegen-x87.cc
@@ -218,6 +218,9 @@ void StringCharLoadGenerator::Generate(MacroAssembler* masm,
                                        Register index,
                                        Register result,
                                        Label* call_runtime) {
+  Label indirect_string_loaded;
+  __ bind(&indirect_string_loaded);
+
   // Fetch the instance type of the receiver into result register.
   __ mov(result, FieldOperand(string, HeapObject::kMapOffset));
   __ movzx_b(result, FieldOperand(result, Map::kInstanceTypeOffset));
@@ -228,17 +231,24 @@ void StringCharLoadGenerator::Generate(MacroAssembler* masm,
   __ j(zero, &check_sequential, Label::kNear);
 
   // Dispatch on the indirect string shape: slice or cons.
-  Label cons_string;
-  __ test(result, Immediate(kSlicedNotConsMask));
-  __ j(zero, &cons_string, Label::kNear);
+  Label cons_string, thin_string;
+  __ and_(result, Immediate(kStringRepresentationMask));
+  __ cmp(result, Immediate(kConsStringTag));
+  __ j(equal, &cons_string, Label::kNear);
+  __ cmp(result, Immediate(kThinStringTag));
+  __ j(equal, &thin_string, Label::kNear);
 
   // Handle slices.
-  Label indirect_string_loaded;
   __ mov(result, FieldOperand(string, SlicedString::kOffsetOffset));
   __ SmiUntag(result);
   __ add(index, result);
   __ mov(string, FieldOperand(string, SlicedString::kParentOffset));
-  __ jmp(&indirect_string_loaded, Label::kNear);
+  __ jmp(&indirect_string_loaded);
+
+  // Handle thin strings.
+  __ bind(&thin_string);
+  __ mov(string, FieldOperand(string, ThinString::kActualOffset));
+  __ jmp(&indirect_string_loaded);
 
   // Handle cons strings.
   // Check whether the right hand side is the empty string (i.e. if
@@ -250,10 +260,7 @@ void StringCharLoadGenerator::Generate(MacroAssembler* masm,
          Immediate(factory->empty_string()));
   __ j(not_equal, call_runtime);
   __ mov(string, FieldOperand(string, ConsString::kFirstOffset));
-
-  __ bind(&indirect_string_loaded);
-  __ mov(result, FieldOperand(string, HeapObject::kMapOffset));
-  __ movzx_b(result, FieldOperand(result, Map::kInstanceTypeOffset));
+  __ jmp(&indirect_string_loaded);
 
   // Distinguish sequential and external strings. Only these two string
   // representations can reach here (slices and flat cons strings have been