In MacroAssembler::JumpIfNotBothSequentialAsciiStrings a custom mask

src/mips/macro-assembler-mips.cc

Index: src/mips/macro-assembler-mips.cc
diff --git a/src/mips/macro-assembler-mips.cc b/src/mips/macro-assembler-mips.cc
index 8a44185ed70a5e48b682c2816b60821da3343c44..1eaa98639f58433102102e4e455d9bab2e29bcc7 100644
--- a/src/mips/macro-assembler-mips.cc
+++ b/src/mips/macro-assembler-mips.cc
@@ -4970,7 +4970,11 @@ void MacroAssembler::JumpIfBothInstanceTypesAreNotSequentialAscii(
     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));