MIPS: Remove move ascii data hint for one byte strings

Port r13375 (198859e8)

Original commit message:
This is mostly a rollback of r12966 [Make kAsciiDataHintTag have correct semantics for all both 1 and 2 byte string types.]

BUG=
TEST=

Review URL: https://chromiumcodereview.appspot.com/11969004
Patch from Akos Palfi <palfia@homejinni.com>.

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@13390 ce2b1a6d-e550-0410-aec6-3dcde31c8c00

src/mips/code-stubs-mips.cc

@@ -6684,6 +6684,11 @@ void StringAddStub::Generate(MacroAssembler* masm) {
   __ And(at, t0, Operand(kAsciiDataHintMask));
   __ and_(at, at, t1);
   __ Branch(&ascii_data, ne, at, Operand(zero_reg));
+  __ Xor(t0, t0, Operand(t1));
+  STATIC_ASSERT(kOneByteStringTag != 0 && kAsciiDataHintTag != 0);
+  __ And(t0, t0, Operand(kOneByteStringTag | kAsciiDataHintTag));
+  __ Branch(&ascii_data, eq, t0,
+      Operand(kOneByteStringTag | kAsciiDataHintTag));
 
   // Allocate a two byte cons string.
   __ AllocateTwoByteConsString(v0, t2, t0, t1, &call_runtime);

src/mips/macro-assembler-mips.cc

@@ -4944,10 +4944,8 @@ void MacroAssembler::JumpIfBothInstanceTypesAreNotSequentialAscii(
     Register scratch2,
     Label* failure) {
   int kFlatAsciiStringMask =
-      kIsNotStringMask | kStringEncodingMask | kAsciiDataHintMask |
-      kStringRepresentationMask;
+      kIsNotStringMask | kStringEncodingMask | kStringRepresentationMask;
   int kFlatAsciiStringTag = ASCII_STRING_TYPE;
-  ASSERT_EQ(ASCII_STRING_TYPE, ASCII_STRING_TYPE & kFlatAsciiStringMask);
   ASSERT(kFlatAsciiStringTag <= 0xffff);  // Ensure this fits 16-bit immed.
   andi(scratch1, first, kFlatAsciiStringMask);
   Branch(failure, ne, scratch1, Operand(kFlatAsciiStringTag));
@@ -4960,10 +4958,8 @@ void MacroAssembler::JumpIfInstanceTypeIsNotSequentialAscii(Register type,
                                                             Register scratch,
                                                             Label* failure) {
   int kFlatAsciiStringMask =
-      kIsNotStringMask | kStringEncodingMask | kAsciiDataHintMask |
-      kStringRepresentationMask;
+      kIsNotStringMask | kStringEncodingMask | kStringRepresentationMask;
   int kFlatAsciiStringTag = ASCII_STRING_TYPE;
-  ASSERT_EQ(ASCII_STRING_TYPE, ASCII_STRING_TYPE & kFlatAsciiStringMask);
   And(scratch, type, Operand(kFlatAsciiStringMask));
   Branch(failure, ne, scratch, Operand(kFlatAsciiStringTag));
 }