Add a premonomorphic state to the call target cache.

src/arm/code-stubs-arm.cc

 // Copyright 2012 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 2999 matching lines @@
   // r0 : number of arguments to the construct function
   // r1 : the function to call
   // r2 : Feedback vector
   // r3 : slot in feedback vector (Smi)
   Label initialize, done, miss, megamorphic, not_array_function;
 
   ASSERT_EQ(*TypeFeedbackInfo::MegamorphicSentinel(masm->isolate()),
             masm->isolate()->heap()->undefined_value());
   ASSERT_EQ(*TypeFeedbackInfo::UninitializedSentinel(masm->isolate()),
             masm->isolate()->heap()->the_hole_value());
+  ASSERT_EQ(*TypeFeedbackInfo::PremonomorphicSentinel(masm->isolate()),
+            masm->isolate()->heap()->null_value());
 
   // Load the cache state into r4.
   __ add(r4, r2, Operand::PointerOffsetFromSmiKey(r3));
   __ ldr(r4, FieldMemOperand(r4, FixedArray::kHeaderSize));
 
   // A monomorphic cache hit or an already megamorphic state: invoke the
   // function without changing the state.
   __ cmp(r4, r1);
   __ b(eq, &done);
 
   // If we came here, we need to see if we are the array function.
   // If we didn't have a matching function, and we didn't find the megamorph
   // sentinel, then we have in the slot either some other function or an
   // AllocationSite. Do a map check on the object in ecx.
   __ ldr(r5, FieldMemOperand(r4, 0));
   __ CompareRoot(r5, Heap::kAllocationSiteMapRootIndex);
   __ b(ne, &miss);
 
   // Make sure the function is the Array() function
   __ LoadArrayFunction(r4);
   __ cmp(r1, r4);
   __ b(ne, &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;
   __ CompareRoot(r4, Heap::kTheHoleValueRootIndex);
+  __ b(ne, &not_uninitialized);
+
+  // PremonomorphicSentinel is an immortal immovable object (null) so no
+  // write-barrier is needed.
+  __ add(r4, r2, Operand::PointerOffsetFromSmiKey(r3));
+  __ LoadRoot(ip, Heap::kNullValueRootIndex);
+  __ str(ip, FieldMemOperand(r4, FixedArray::kHeaderSize));
+  __ 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);
+  __ CompareRoot(r4, Heap::kNullValueRootIndex);
   __ b(eq, &initialize);
+
   // MegamorphicSentinel is an immortal immovable object (undefined) so no
   // write-barrier is needed.
   __ bind(&megamorphic);
   __ add(r4, r2, Operand::PointerOffsetFromSmiKey(r3));
   __ LoadRoot(ip, Heap::kUndefinedValueRootIndex);
   __ str(ip, FieldMemOperand(r4, FixedArray::kHeaderSize));
   __ jmp(&done);
 
   // An uninitialized cache is patched with the function or sentinel to
   // indicate the ElementsKind if function is the Array constructor.
@@ skipping 2514 matching lines @@
                               MemOperand(fp, 6 * kPointerSize),
                               NULL);
 }
 
 
 #undef __
 
 } }  // namespace v8::internal
 
 #endif  // V8_TARGET_ARCH_ARM