Revert of Internalize strings in-place

src/mips64/code-stubs-mips64.cc

Index: src/mips64/code-stubs-mips64.cc
diff --git a/src/mips64/code-stubs-mips64.cc b/src/mips64/code-stubs-mips64.cc
index 9e56dfd1bd5fb235b143c9e95590cabfdc0bdb82..8575604f1d1700a9b19cec7262ae9d205bfbb523 100644
--- a/src/mips64/code-stubs-mips64.cc
+++ b/src/mips64/code-stubs-mips64.cc
@@ -1420,7 +1420,7 @@ void RegExpExecStub::Generate(MacroAssembler* masm) {
   // (6) External string.  Make it, offset-wise, look like a sequential string.
   //     Go to (4).
   // (7) Short external string or not a string?  If yes, bail out to runtime.
-  // (8) Sliced or thin string.  Replace subject with parent.  Go to (1).
+  // (8) Sliced string.  Replace subject with parent.  Go to (1).
 
   Label check_underlying;   // (1)
   Label seq_string;         // (4)
@@ -1444,7 +1444,6 @@ void RegExpExecStub::Generate(MacroAssembler* masm) {
   // (2) Sequential or cons?  If not, go to (5).
   STATIC_ASSERT(kConsStringTag < kExternalStringTag);
   STATIC_ASSERT(kSlicedStringTag > kExternalStringTag);
-  STATIC_ASSERT(kThinStringTag > kExternalStringTag);
   STATIC_ASSERT(kIsNotStringMask > kExternalStringTag);
   STATIC_ASSERT(kShortExternalStringTag > kExternalStringTag);
   // Go to (5).
@@ -1471,8 +1470,8 @@ void RegExpExecStub::Generate(MacroAssembler* masm) {
   __ Branch(&runtime, ls, a3, Operand(a1));
   __ SmiUntag(a1);
 
-  STATIC_ASSERT(kStringEncodingMask == 8);
-  STATIC_ASSERT(kOneByteStringTag == 8);
+  STATIC_ASSERT(kStringEncodingMask == 4);
+  STATIC_ASSERT(kOneByteStringTag == 4);
   STATIC_ASSERT(kTwoByteStringTag == 0);
   __ And(a0, a0, Operand(kStringEncodingMask));  // Non-zero for one_byte.
   __ ld(t9, FieldMemOperand(regexp_data, JSRegExp::kDataOneByteCodeOffset));
@@ -1722,18 +1721,12 @@ void RegExpExecStub::Generate(MacroAssembler* masm) {
   __ And(at, a1, Operand(kIsNotStringMask | kShortExternalStringMask));
   __ Branch(&runtime, ne, at, Operand(zero_reg));
 
-  // (8) Sliced or thin string.  Replace subject with parent.  Go to (4).
-  Label thin_string;
-  __ Branch(&thin_string, eq, a1, Operand(kThinStringTag));
+  // (8) Sliced string.  Replace subject with parent.  Go to (4).
   // Load offset into t0 and replace subject string with parent.
   __ ld(t0, FieldMemOperand(subject, SlicedString::kOffsetOffset));
   __ SmiUntag(t0);
   __ ld(subject, FieldMemOperand(subject, SlicedString::kParentOffset));
   __ jmp(&check_underlying);  // Go to (1).
-
-  __ bind(&thin_string);
-  __ ld(subject, FieldMemOperand(subject, ThinString::kActualOffset));
-  __ jmp(&check_underlying);  // Go to (1).
 #endif  // V8_INTERPRETED_REGEXP
 }