Remove the different length string types...

src/x64/codegen-x64.cc

 // Copyright 2009 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 3749 matching lines @@
   __ SmiToInteger32(index.reg(), index.reg());
 
   __ bind(&try_again_with_new_string);
   // Fetch the instance type of the receiver into rcx.
   __ movq(rcx, FieldOperand(object.reg(), HeapObject::kMapOffset));
   __ movzxbl(rcx, FieldOperand(rcx, Map::kInstanceTypeOffset));
   // If the receiver is not a string trigger the slow case.
   __ testb(rcx, Immediate(kIsNotStringMask));
   __ j(not_zero, &slow_case);
 
-  // Here we make assumptions about the tag values and the shifts needed.
-  // See the comment in objects.h.
-  ASSERT(kLongStringTag == 0);
-  ASSERT(kMediumStringTag + String::kLongLengthShift ==
-         String::kMediumLengthShift);
-  ASSERT(kShortStringTag + String::kLongLengthShift ==
-         String::kShortLengthShift);
-  __ and_(rcx, Immediate(kStringSizeMask));
-  __ addq(rcx, Immediate(String::kLongLengthShift));
-  // Fetch the length field into the temporary register.
-  __ movl(temp.reg(), FieldOperand(object.reg(), String::kLengthOffset));
-  __ shrl_cl(temp.reg());
   // Check for index out of range.
-  __ cmpl(index.reg(), temp.reg());
+  __ cmpl(index.reg(), FieldOperand(object.reg(), String::kLengthOffset));
   __ j(greater_equal, &slow_case);
   // Reload the instance type (into the temp register this time)..
   __ movq(temp.reg(), FieldOperand(object.reg(), HeapObject::kMapOffset));
   __ movzxbl(temp.reg(), FieldOperand(temp.reg(), Map::kInstanceTypeOffset));
 
   // We need special handling for non-flat strings.
   ASSERT_EQ(0, kSeqStringTag);
   __ testb(temp.reg(), Immediate(kStringRepresentationMask));
   __ j(not_zero, &not_a_flat_string);
   // Check for 1-byte or 2-byte string.
@@ skipping 2374 matching lines @@
   __ and_(rbx, Immediate(1 << Map::kIsUndetectable));
   __ j(not_zero, &false_result);
 
   // JavaScript object => true.
   __ cmpq(rcx, Immediate(FIRST_JS_OBJECT_TYPE));
   __ j(above_equal, &true_result);
 
   // String value => false iff empty.
   __ cmpq(rcx, Immediate(FIRST_NONSTRING_TYPE));
   __ j(above_equal, &not_string);
-  __ and_(rcx, Immediate(kStringSizeMask));
-  __ cmpq(rcx, Immediate(kShortStringTag));
-  __ j(not_equal, &true_result);  // Empty string is always short.
   __ movl(rdx, FieldOperand(rax, String::kLengthOffset));
-  __ shr(rdx, Immediate(String::kShortLengthShift));
+  __ testl(rdx, rdx);
   __ j(zero, &false_result);
   __ jmp(&true_result);
 
   __ bind(&not_string);
   // HeapNumber => false iff +0, -0, or NaN.
   // These three cases set C3 when compared to zero in the FPU.
   __ CompareRoot(rdx, Heap::kHeapNumberMapRootIndex);
   __ j(not_equal, &true_result);
   __ fldz();  // Load zero onto fp stack
   // Load heap-number double value onto fp stack
@@ skipping 1693 matching lines @@
   masm.GetCode(&desc);
   // Call the function from C++.
   return FUNCTION_CAST<ModuloFunction>(buffer);
 }
 
 #endif
 
 #undef __
 
 } }  // namespace v8::internal