Revert of Internalize strings in-place

src/s390/code-stubs-s390.cc

Index: src/s390/code-stubs-s390.cc
diff --git a/src/s390/code-stubs-s390.cc b/src/s390/code-stubs-s390.cc
index 8016b327e2da86d9d2cae1de0862d2649a4580d2..dbbb7e32dd04f918415dbf5b4f5d9118a8aae589 100644
--- a/src/s390/code-stubs-s390.cc
+++ b/src/s390/code-stubs-s390.cc
@@ -1371,7 +1371,7 @@ 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 seq_string /* 4 */, external_string /* 6 */, check_underlying /* 1 */,
       not_seq_nor_cons /* 5 */, not_long_external /* 7 */;
@@ -1393,7 +1393,6 @@ 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);
   STATIC_ASSERT(kExternalStringTag < 0xffffu);
@@ -1681,19 +1680,12 @@ void RegExpExecStub::Generate(MacroAssembler* masm) {
   __ AndP(r0, r3);
   __ bne(&runtime);
 
-  // (8) Sliced or thin string.  Replace subject with parent.  Go to (4).
-  Label thin_string;
-  __ CmpP(r3, Operand(kThinStringTag));
-  __ beq(&thin_string);
+  // (8) Sliced string.  Replace subject with parent.  Go to (4).
   // Load offset into ip and replace subject string with parent.
   __ LoadP(ip, FieldMemOperand(subject, SlicedString::kOffsetOffset));
   __ SmiUntag(ip);
   __ LoadP(subject, FieldMemOperand(subject, SlicedString::kParentOffset));
   __ b(&check_underlying);  // Go to (4).
-
-  __ bind(&thin_string);
-  __ LoadP(subject, FieldMemOperand(subject, ThinString::kActualOffset));
-  __ b(&check_underlying);  // Go to (4).
 #endif  // V8_INTERPRETED_REGEXP
 }