Adapt Danno's Track Allocation Info idea to fast literals. When allocating a literal array,

src/x64/codegen-x64.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 265 matching lines @@
   // ----------- S t a t e -------------
   //  -- rax    : value
   //  -- rbx    : target map
   //  -- rcx    : key
   //  -- rdx    : receiver
   //  -- rsp[0] : return address
   // -----------------------------------
   // The fail label is not actually used since we do not allocate.
   Label allocated, new_backing_store, only_change_map, done;
 
+  if (FLAG_use_allocation_site_info) {
+    masm->PerformAllocationSiteInfoCheck(fail);
+  }
+
   // Check for empty arrays, which only require a map transition and no changes
   // to the backing store.
   __ movq(r8, FieldOperand(rdx, JSObject::kElementsOffset));
   __ CompareRoot(r8, Heap::kEmptyFixedArrayRootIndex);
   __ j(equal, &only_change_map);
 
   // Check backing store for COW-ness.  For COW arrays we have to
   // allocate a new backing store.
   __ SmiToInteger32(r9, FieldOperand(r8, FixedDoubleArray::kLengthOffset));
   __ CompareRoot(FieldOperand(r8, HeapObject::kMapOffset),
@@ skipping 101 matching lines @@
     MacroAssembler* masm, Label* fail) {
   // ----------- S t a t e -------------
   //  -- rax    : value
   //  -- rbx    : target map
   //  -- rcx    : key
   //  -- rdx    : receiver
   //  -- rsp[0] : return address
   // -----------------------------------
   Label loop, entry, convert_hole, gc_required, only_change_map;
 
+  // TODO(mvstanton): let's not pre-transition for the double->object case.
+  // if (FLAG_use_allocation_site_info) {
+  //   masm->PerformAllocationSiteInfoCheck(fail);
+  // }

[danno, 2013/01/04 08:50:55]

Remove

+
   // Check for empty arrays, which only require a map transition and no changes
   // to the backing store.
   __ movq(r8, FieldOperand(rdx, JSObject::kElementsOffset));
   __ CompareRoot(r8, Heap::kEmptyFixedArrayRootIndex);
   __ j(equal, &only_change_map);
 
   __ push(rax);
 
   __ movq(r8, FieldOperand(rdx, JSObject::kElementsOffset));
   __ SmiToInteger32(r9, FieldOperand(r8, FixedDoubleArray::kLengthOffset));
@@ skipping 341 matching lines @@
     CodePatcher patcher(sequence, young_length);
     patcher.masm()->call(stub->instruction_start());
     patcher.masm()->nop();
   }
 }
 
 
 } }  // namespace v8::internal
 
 #endif  // V8_TARGET_ARCH_X64