A64: Support the --deopt_every_n_times flag.

src/a64/lithium-codegen-a64.cc

 // Copyright 2013 the V8 project authors. All rights reserved.
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 // modification, are permitted provided that the following conditions are
 // met:
 //
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@@ skipping 866 matching lines @@
   ASSERT(info()->IsOptimizing() || info()->IsStub());
   int id = environment->deoptimization_index();
   Address entry =
       Deoptimizer::GetDeoptimizationEntry(isolate(), id, bailout_type);
 
   if (entry == NULL) {
     Abort("bailout was not prepared");
     return;
   }
 
-  TODO_UNIMPLEMENTED("Add support for deopt_every_n_times flag.");
+  ASSERT(FLAG_deopt_every_n_times < 2);  // Other values not supported on A64.
+  if (FLAG_deopt_every_n_times == 1 &&
+      !info()->IsStub() &&
+      info()->opt_count() == id) {
+    __ Jump(entry, RelocInfo::RUNTIME_ENTRY);
+    return;
+  }
+
   if (FLAG_trap_on_deopt && info()->IsOptimizing()) {
     __ Debug("trap_on_deopt", __LINE__, BREAK);
   }
 
 
   // TODO(all): Currently this code directly jump to the second level deopt
   // table entry. This code need to be updated if we decide to use the
   // 2 levels of table.
   ASSERT(info()->IsStub() || frame_is_built_);
   bool needs_lazy_deopt = info()->IsStub();
@@ skipping 4678 matching lines @@
   __ Bind(&out_of_object);
   __ Ldr(result, FieldMemOperand(object, JSObject::kPropertiesOffset));
   // Index is equal to negated out of object property index plus 1.
   __ Sub(result, result, Operand::UntagSmiAndScale(index, kPointerSizeLog2));
   __ Ldr(result, FieldMemOperand(result,
                                  FixedArray::kHeaderSize - kPointerSize));
   __ Bind(&done);
 }
 
 } }  // namespace v8::internal