Investigate & fix issues around usage_count and deoptimization_count

runtime/vm/object.cc

 // Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 #include "vm/object.h"
 
 #include "include/dart_api.h"
 #include "platform/assert.h"
 #include "vm/assembler.h"
 #include "vm/cpu.h"
@@ skipping 2779 matching lines @@
 
 
 #if defined(DEBUG)
 static bool IsMutatorOrAtSafepoint() {
   Thread* thread = Thread::Current();
   return thread->IsMutatorThread() ||
          thread->isolate()->thread_registry()->AtSafepoint();
 }
 #endif
 
+
 void Class::RegisterCHACode(const Code& code) {
   if (FLAG_trace_cha) {
-    THR_Print("RegisterCHACode %s class %s\n",
+    THR_Print("RegisterCHACode '%s' depends on class '%s'\n",
         Function::Handle(code.function()).ToQualifiedCString(), ToCString());
   }
   DEBUG_ASSERT(IsMutatorOrAtSafepoint());
   ASSERT(code.is_optimized());
   CHACodeArray a(*this);
   a.Register(code);
 }
 
 
-void Class::DisableCHAOptimizedCode() {
+void Class::DisableCHAOptimizedCode(const Class& subclass) {
   ASSERT(Thread::Current()->IsMutatorThread());
   CHACodeArray a(*this);
-  a.DisableCode();

[Florian Schneider, 2016/01/04 11:31:38]

What about the other call-sites of DisableCode()? Also check HasCodes there?

+  if (a.HasCodes()) {

[Florian Schneider, 2016/01/04 11:31:38]

If you always check HasCodes before calling DisableCode, maybe add an ASSERT
inside DisableCode()

ASSERT(HasCodes())

and remove the check for a null code array there.

[srdjan, 2016/01/04 18:29:53]

What I really meant to do (and changed it to):

  CHACodeArray a(*this);
  if (FLAG_trace_deoptimization && a.HasCodes()) {
    THR_Print("Adding subclass %s\n", subclass.ToCString());
  }
  a.DisableCode();

No need to guard calling 'DisableCode', let it handle it itself (more robust).

+    if (FLAG_trace_deoptimization) {
+      THR_Print("Adding subclass %s\n", subclass.ToCString());
+    }
+    a.DisableCode();
+  }
 }
 
 
 bool Class::TraceAllocation(Isolate* isolate) const {
   ClassTable* class_table = isolate->class_table();
   return class_table->TraceAllocationFor(id());
 }
 
 
 void Class::SetTraceAllocation(bool trace_allocation) const {
@@ skipping 2987 matching lines @@
     return false;
   }
   if (is_native()) {
     // Native methods don't need to be optimized.
     return false;
   }
   if (is_optimizable() && (script() != Script::null()) &&
       ((end_token_pos() - token_pos()) < FLAG_huge_method_cutoff_in_tokens)) {
     // Additional check needed for implicit getters.
     return (unoptimized_code() == Object::null()) ||
-           (Code::Handle(unoptimized_code()).Size() <
+        (Code::Handle(unoptimized_code()).Size() <
             FLAG_huge_method_cutoff_in_code_size);
   }
   return false;
 }
 
 
 bool Function::IsNativeAutoSetupScope() const {
   return is_native() ? is_optimizable() : false;
 }
 
 
 void Function::SetIsOptimizable(bool value) const {
   ASSERT(!is_native());
   set_is_optimizable(value);
   if (!value) {
     set_is_inlinable(false);
+    set_usage_counter(INT_MIN);
   }
 }
 
 
 void Function::SetIsNativeAutoSetupScope(bool value) const {
   ASSERT(is_native());
   set_is_optimizable(value);
 }
 
 
@@ skipping 16146 matching lines @@
   return tag_label.ToCString();
 }
 
 
 void UserTag::PrintJSONImpl(JSONStream* stream, bool ref) const {
   Instance::PrintJSONImpl(stream, ref);
 }
 
 
 }  // namespace dart