Add counters for write barriers in optimized code.

src/x64/macro-assembler-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 395 matching lines @@
   }
 
   if (emit_debug_code()) {
     Label ok;
     cmpq(value, Operand(address, 0));
     j(equal, &ok, Label::kNear);
     int3();
     bind(&ok);
   }
 
+  // Count number of write barriers in generated code.
+  isolate()->counters()->write_barriers_static()->Increment();
+  IncrementCounter(isolate()->counters()->write_barriers_dynamic(), 1);
+
   // First, check if a write barrier is even needed. The tests below
   // catch stores of smis and stores into the young generation.
   Label done;
 
   if (smi_check == INLINE_SMI_CHECK) {
     // Skip barrier if writing a smi.
     JumpIfSmi(value, &done);
   }
 
   CheckPageFlag(value,
@@ skipping 4503 matching lines @@
   j(greater, &no_memento_available);
   CompareRoot(MemOperand(scratch_reg, -AllocationMemento::kSize),
               Heap::kAllocationMementoMapRootIndex);
   bind(&no_memento_available);
 }
 
 
 } }  // namespace v8::internal
 
 #endif  // V8_TARGET_ARCH_X64