In MacroAssembler::JumpIfNotBothSequentialAsciiStrings a custom mask

src/arm/macro-assembler-arm.cc

Index: src/arm/macro-assembler-arm.cc
diff --git a/src/arm/macro-assembler-arm.cc b/src/arm/macro-assembler-arm.cc
index 8416926b46adaccce279e32ab64dd7ad85f2677c..ee4b7fa73aab0d651c31f0aa1caf5f2b1d477265 100644
--- a/src/arm/macro-assembler-arm.cc
+++ b/src/arm/macro-assembler-arm.cc
@@ -3262,7 +3262,11 @@ 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;

[Yang, 2013/07/22 09:09:46]

I actually prefer not to use the defined instance type, but instead something
corresponding to the mask:

kStringTag | kOneByteStringTag | kSeqStringTag

[mvstanton, 2013/07/22 09:40:17]

Done.

   and_(scratch1, first, Operand(kFlatAsciiStringMask));
   and_(scratch2, second, Operand(kFlatAsciiStringMask));
   cmp(scratch1, Operand(kFlatAsciiStringTag));