MIPS: port RegExpMacroAssembler::CheckStackGuardState should update input string pointer...

... when it is moved or changed by GC.

Port r9697 (d53382a)

BUG=
TEST=

Review URL: http://codereview.chromium.org/8362024
Patch from Paul Lind <plind44@gmail.com>.

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@9740 ce2b1a6d-e550-0410-aec6-3dcde31c8c00

src/mips/regexp-macro-assembler-mips.cc

@@ -1112,6 +1112,11 @@ int RegExpMacroAssemblerMIPS::CheckStackGuardState(Address* return_address,
     frame_entry<const String*>(re_frame, kInputString) = *subject;
     frame_entry<const byte*>(re_frame, kInputStart) = new_address;
     frame_entry<const byte*>(re_frame, kInputEnd) = new_address + byte_length;
+  } else if (frame_entry<const String*>(re_frame, kInputString) != *subject) {
+    // Subject string might have been a ConsString that underwent
+    // short-circuiting during GC. That will not change start_address but
+    // will change pointer inside the subject handle.
+    frame_entry<const String*>(re_frame, kInputString) = *subject;
   }
 
   return 0;