Introduce code flushing of RegExp code.

src/x64/code-stubs-x64.cc

 // Copyright 2011 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 2436 matching lines @@
 
   __ bind(&seq_two_byte_string);
   // rdi: subject string (flat two-byte)
   // rax: RegExp data (FixedArray)
   __ movq(r11, FieldOperand(rax, JSRegExp::kDataUC16CodeOffset));
   __ Set(rcx, 0);  // Type is two byte.
 
   __ bind(&check_code);
   // Check that the irregexp code has been generated for the actual string
   // encoding. If it has, the field contains a code object otherwise it contains
-  // the hole.
-  __ CmpObjectType(r11, CODE_TYPE, kScratchRegister);
-  __ j(not_equal, &runtime);
+  // smi (code flushing support)
+  __ JumpIfSmi(r11, &runtime);
 
   // rdi: subject string
   // rcx: encoding of subject string (1 if ascii, 0 if two_byte);
   // r11: code
   // Load used arguments before starting to push arguments for call to native
   // RegExp code to avoid handling changing stack height.
   __ SmiToInteger64(rbx, Operand(rsp, kPreviousIndexOffset));
 
   // rdi: subject string
   // rbx: previous index
@@ skipping 2869 matching lines @@
   __ Drop(1);
   __ ret(2 * kPointerSize);
 }
 
 
 #undef __
 
 } }  // namespace v8::internal
 
 #endif  // V8_TARGET_ARCH_X64