Add a premonomorphic state to the call target cache.

src/x64/code-stubs-x64.cc

 // Copyright 2013 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 2183 matching lines @@
   __ j(not_equal, &miss);
 
   // Make sure the function is the Array() function
   __ LoadArrayFunction(rcx);
   __ cmpq(rdi, rcx);
   __ j(not_equal, &megamorphic);
   __ jmp(&done);
 
   __ bind(&miss);
 
-  // A monomorphic miss (i.e, here the cache is not uninitialized) goes
-  // megamorphic.
+  // A monomorphic miss (i.e, here the cache is not uninitialized or
+  // pre-monomorphic) goes megamorphic.
+  Label not_uninitialized;
   __ Cmp(rcx, TypeFeedbackInfo::UninitializedSentinel(isolate));
+  __ j(not_equal, &not_uninitialized);
+
+  // PremonomorphicSentinel is an immortal immovable object (null) so no
+  // write-barrier is needed.
+  __ Move(FieldOperand(rbx, rdx, times_pointer_size, FixedArray::kHeaderSize),
+          TypeFeedbackInfo::PremonomorphicSentinel(isolate));
+  __ jmp(&done);
+
+  // If the cache isn't uninitialized, it is either premonomorphic or
+  // monomorphic. If it is premonomorphic, we initialize it thus making
+  // it monomorphic. Otherwise, we go megamorphic.
+  __ bind(&not_uninitialized);
+  __ Cmp(rcx, TypeFeedbackInfo::PremonomorphicSentinel(isolate));
   __ j(equal, &initialize);
+
   // MegamorphicSentinel is an immortal immovable object (undefined) so no
   // write-barrier is needed.
   __ bind(&megamorphic);
   __ Move(FieldOperand(rbx, rdx, times_pointer_size, FixedArray::kHeaderSize),
           TypeFeedbackInfo::MegamorphicSentinel(isolate));
   __ jmp(&done);
 
   // An uninitialized cache is patched with the function or sentinel to
   // indicate the ElementsKind if function is the Array constructor.
   __ bind(&initialize);
@@ skipping 3109 matching lines @@
                               return_value_operand,
                               NULL);
 }
 
 
 #undef __
 
 } }  // namespace v8::internal
 
 #endif  // V8_TARGET_ARCH_X64