When methods cannot be optimized initialize their count to a large negative number, otherwise they …

runtime/vm/code_generator.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/code_generator.h"
 
 #include "vm/assembler_macros.h"
 #include "vm/code_patcher.h"
 #include "vm/compiler.h"
 #include "vm/dart_api_impl.h"
@@ skipping 1298 matching lines @@
       }
     }
   }
 }
 
 
 // Only unoptimized code has invocation counter threshold checking.
 // Once the invocation counter threshold is reached any entry into the
 // unoptimized code is redirected to this function.
 DEFINE_RUNTIME_ENTRY(OptimizeInvokedFunction, 1) {
+  const intptr_t kLowInvocationCount = -100000000;

[siva, 2012/05/24 23:44:22]

Why this value and not kIntptrMin....

[srdjan, 2012/05/24 23:57:22]

It must be a Smi, could have been MinSmi but this number is as nice.

   ASSERT(arguments.Count() ==
          kOptimizeInvokedFunctionRuntimeEntry.argument_count());
   const Function& function = Function::CheckedHandle(arguments.At(0));
   if (isolate->debugger()->IsActive()) {
     // We cannot set breakpoints in optimized code, so do not optimize
     // the function.
     function.set_usage_counter(0);
     return;
   }
   if (function.deoptimization_counter() >=
       FLAG_deoptimization_counter_threshold) {
     // TODO(srdjan): Investigate excessive deoptimization.
-    function.set_usage_counter(0);
+    function.set_usage_counter(kLowInvocationCount);
     return;
   }
   if (function.HasOptimizedCode()) {
     // The caller has been already optimized.
     // TODO(srdjan): This is a significant slowdown, the caller is probably in
     // a loop. Maybe test if the code has been optimized before calling.
     // If this happens from optimized code, then it means that the optimized
     // code needs to be reoptimized.
-    function.set_usage_counter(0);
+    function.set_usage_counter(kLowInvocationCount);
     return;
   }
   if (function.is_optimizable()) {
     ASSERT(!function.HasOptimizedCode());
     const Code& unoptimized_code = Code::Handle(function.unoptimized_code());
     // Compilation patches the entry of unoptimized code.
     const Error& error =
         Error::Handle(Compiler::CompileOptimizedFunction(function));
     if (!error.IsNull()) {
       Exceptions::PropagateError(error);
     }
     const Code& optimized_code = Code::Handle(function.CurrentCode());
     ASSERT(!optimized_code.IsNull());
     ASSERT(!unoptimized_code.IsNull());
   } else {
     // TODO(5442338): Abort as this should not happen.
-    function.set_usage_counter(0);
+    function.set_usage_counter(kLowInvocationCount);
   }
 }
 
 
 // The caller must be a static call in a Dart frame, or an entry frame.
 // Patch static call to point to 'new_entry_point'.
 DEFINE_RUNTIME_ENTRY(FixCallersTarget, 1) {
   ASSERT(arguments.Count() == kFixCallersTargetRuntimeEntry.argument_count());
   const Function& function = Function::CheckedHandle(arguments.At(0));
   ASSERT(!function.IsNull());
@@ skipping 186 matching lines @@
       }
     }
   }
   // The cache is null terminated, therefore the loop above should never
   // terminate by itself.
   UNREACHABLE();
   return Code::null();
 }
 
 }  // namespace dart