In MacroAssembler::JumpIfNotBothSequentialAsciiStrings a custom mask

src/ia32/macro-assembler-ia32.cc

Index: src/ia32/macro-assembler-ia32.cc
diff --git a/src/ia32/macro-assembler-ia32.cc b/src/ia32/macro-assembler-ia32.cc
index ef90c10df0d1a2b414d630c724f8e14646a4ed00..5165e1fc6c4c1ddbc32039d4ac8d6d41f1984954 100644
--- a/src/ia32/macro-assembler-ia32.cc
+++ b/src/ia32/macro-assembler-ia32.cc
@@ -2798,7 +2798,11 @@ void MacroAssembler::JumpIfNotBothSequentialAsciiStrings(Register object1,
   // Check that both are flat ASCII strings.
   const int kFlatAsciiStringMask =
       kIsNotStringMask | kStringRepresentationMask | kStringEncodingMask;
-  const 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;
   // Interleave bits from both instance types and compare them in one check.
   ASSERT_EQ(0, kFlatAsciiStringMask & (kFlatAsciiStringMask << 3));
   and_(scratch1, kFlatAsciiStringMask);