x64: Enable inline smi code patching to reenable the inlined code in

src/x64/ic-x64.cc

 // Copyright 2010 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 1689 matching lines @@
   set_target(*rewritten);
 
 #ifdef DEBUG
   if (FLAG_trace_ic) {
     PrintF("[CompareIC (%s->%s)#%s]\n",
            GetStateName(previous_state),
            GetStateName(state),
            Token::Name(op_));
   }
 #endif
+
+  // Activate inlined smi code.
+  if (previous_state == UNINITIALIZED) {
+    PatchInlinedSmiCode(address());
+  }
 }
 
 void PatchInlinedSmiCode(Address address) {
-  // Disabled, then patched inline smi code is not implemented on X64.
-  // So we do nothing in this case.
+  // The address of the instruction following the call.
+  Address test_instruction_address =
+      address + Assembler::kCallTargetAddressOffset;
+
+  // If the instruction following the call is not a test al, nothing
+  // was inlined.
+  if (*test_instruction_address != Assembler::kTestAlByte) {
+    ASSERT(*test_instruction_address == Assembler::kNopByte);
+    return;
+  }
+
+  Address delta_address = test_instruction_address + 1;
+  // The delta to the start of the map check instruction and the
+  // condition code uses at the patched jump.
+  int8_t delta = *reinterpret_cast<int8_t*>(delta_address);
+  if (FLAG_trace_ic) {
+    PrintF("[  patching ic at %p, test=%p, delta=%d\n",
+           address, test_instruction_address, delta);
+  }
+
+  // Patch with a short conditional jump. There must be a
+  // short jump-if-carry/not-carry at this position.
+  Address jmp_address = test_instruction_address - delta;
+  ASSERT(*jmp_address == Assembler::kJncShortOpcode ||
+         *jmp_address == Assembler::kJcShortOpcode);
+  Condition cc = *jmp_address == Assembler::kJncShortOpcode
+      ? not_zero
+      : zero;
+  *jmp_address = static_cast<byte>(Assembler::kJccShortPrefix | cc);
 }
 
 
 } }  // namespace v8::internal
 
 #endif  // V8_TARGET_ARCH_X64