CallIC customization stubs must accept that a vector slot is cleared.

src/arm64/code-stubs-arm64.cc

 // Copyright 2013 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "src/v8.h"
 
 #if V8_TARGET_ARCH_ARM64
 
 #include "src/bootstrapper.h"
 #include "src/code-stubs.h"
@@ skipping 3212 matching lines @@
   Register feedback_vector = x2;
   Register index = x3;
   Register scratch = x4;
 
   EmitLoadTypeFeedbackVector(masm, feedback_vector);
 
   __ LoadGlobalFunction(Context::ARRAY_FUNCTION_INDEX, scratch);
   __ Cmp(function, scratch);
   __ B(ne, &miss);
 
-  Register allocation_site = feedback_vector;
   __ Mov(x0, Operand(arg_count()));
 
   __ Add(scratch, feedback_vector,
          Operand::UntagSmiAndScale(index, kPointerSizeLog2));
-  __ Ldr(allocation_site, FieldMemOperand(scratch, FixedArray::kHeaderSize));
+  __ Ldr(scratch, FieldMemOperand(scratch, FixedArray::kHeaderSize));
 
-  // Verify that x2 contains an AllocationSite
-  __ AssertUndefinedOrAllocationSite(allocation_site, scratch);
+  // Verify that scratch contains an AllocationSite
+  Register map = x5;
+  __ Ldr(map, FieldMemOperand(scratch, AllocationSite::kMapOffset));

[Toon Verwaest, 2014/07/28 14:11:38]

HeapObject::kMapOffset?
(You don't know yet whether it's an AllocationSite, just that it's a HeapObject)

[mvstanton, 2014/07/28 16:02:50]

Right, we will store in this slot the uninitialized symbol, the megamorphic
symbol, a function pointer or an allocationsite. Since those are all heap
objects with maps, I can dereference here. Changed to HeapObject::kMapOffset.

+  __ JumpIfNotRoot(map, Heap::kAllocationSiteMapRootIndex, &miss);
+
+  Register allocation_site = feedback_vector;
+  __ Mov(allocation_site, scratch);
   ArrayConstructorStub stub(masm->isolate(), arg_count());
   __ TailCallStub(&stub);
 
   __ bind(&miss);
   GenerateMiss(masm, IC::kCallIC_Customization_Miss);
 
   // The slow case, we need this no matter what to complete a call after a miss.
   CallFunctionNoFeedback(masm,
                          arg_count(),
                          true,
@@ skipping 2149 matching lines @@
                               MemOperand(fp, 6 * kPointerSize),
                               NULL);
 }
 
 
 #undef __
 
 } }  // namespace v8::internal
 
 #endif  // V8_TARGET_ARCH_ARM64