In MacroAssembler::JumpIfNotBothSequentialAsciiStrings a custom mask

src/mips/macro-assembler-mips.cc

 // Copyright 2012 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 4952 matching lines @@
 
 
 void MacroAssembler::JumpIfBothInstanceTypesAreNotSequentialAscii(
     Register first,
     Register second,
     Register scratch1,
     Register scratch2,
     Label* failure) {
   int kFlatAsciiStringMask =
       kIsNotStringMask | kStringEncodingMask | kStringRepresentationMask;
-  int kFlatAsciiStringTag = ASCII_STRING_TYPE;
+  // Use ASCII_INTERNALIZED_STRING_TYPE because it's internalized bit is zero.
+  // Since we don't include that bit in the mask above, the test below will
+  // succeed for ASCII_STRING_TYPE and ASCII_INTERNALIZED_STRING_TYPE.
+  STATIC_ASSERT(kInternalizedTag == 0);
+  const int kFlatAsciiStringTag = ASCII_INTERNALIZED_STRING_TYPE;
   ASSERT(kFlatAsciiStringTag <= 0xffff);  // Ensure this fits 16-bit immed.
   andi(scratch1, first, kFlatAsciiStringMask);
   Branch(failure, ne, scratch1, Operand(kFlatAsciiStringTag));
   andi(scratch2, second, kFlatAsciiStringMask);
   Branch(failure, ne, scratch2, Operand(kFlatAsciiStringTag));
 }
 
 
 void MacroAssembler::JumpIfInstanceTypeIsNotSequentialAscii(Register type,
                                                             Register scratch,
@@ skipping 581 matching lines @@
        opcode == BGTZL);
   opcode = (cond == eq) ? BEQ : BNE;
   instr = (instr & ~kOpcodeMask) | opcode;
   masm_.emit(instr);
 }
 
 
 } }  // namespace v8::internal
 
 #endif  // V8_TARGET_ARCH_MIPS