Investigate & fix issues around usage_count and deoptimization_count

runtime/vm/code_generator.cc

 // Copyright (c) 2013, 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.h"
 #include "vm/ast.h"
 #include "vm/code_patcher.h"
 #include "vm/compiler.h"
@@ skipping 1227 matching lines @@
       DartEntry::InvokeNoSuchMethod(receiver,
                                     original_function_name,
                                     orig_arguments,
                                     orig_arguments_desc));
   CheckResultError(result);
   arguments.SetReturn(result);
 }
 
 
 static bool CanOptimizeFunction(const Function& function, Thread* thread) {
-  const intptr_t kLowInvocationCount = -100000000;
   Isolate* isolate = thread->isolate();
   if (isolate->debugger()->IsStepping() ||
       isolate->debugger()->HasBreakpoint(function, thread->zone())) {
     // We cannot set breakpoints and single step in optimized code,
     // so do not optimize the function.
     function.set_usage_counter(0);
     return false;
   }
   if (function.deoptimization_counter() >=
       FLAG_max_deoptimization_counter_threshold) {
     if (FLAG_trace_failed_optimization_attempts ||
         FLAG_stop_on_excessive_deoptimization) {
-      OS::PrintErr("Too Many Deoptimizations: %s\n",
+      THR_Print("Too many deoptimizations: %s\n",
           function.ToFullyQualifiedCString());
       if (FLAG_stop_on_excessive_deoptimization) {
         FATAL("Stop on excessive deoptimization");
       }
     }
-    // TODO(srdjan): Investigate excessive deoptimization.
-    function.set_usage_counter(kLowInvocationCount);
+    // The function will not be optimized any longer. This situation can occur
+    // mostly with small optimization counter thresholds.
+    function.SetIsOptimizable(false);
+    function.set_usage_counter(INT_MIN);
     return false;
   }
   if (FLAG_optimization_filter != NULL) {
     // FLAG_optimization_filter is a comma-separated list of strings that are
     // matched against the fully-qualified function name.
     char* save_ptr;  // Needed for strtok_r.
     const char* function_name = function.ToFullyQualifiedCString();
     intptr_t len = strlen(FLAG_optimization_filter) + 1;  // Length with \0.
     char* filter = new char[len];
     strncpy(filter, FLAG_optimization_filter, len);  // strtok modifies arg 1.
     char* token = strtok_r(filter, ",", &save_ptr);
     bool found = false;
     while (token != NULL) {
       if (strstr(function_name, token) != NULL) {
         found = true;
         break;
       }
       token = strtok_r(NULL, ",", &save_ptr);
     }
     delete[] filter;
     if (!found) {
-      function.set_usage_counter(kLowInvocationCount);
+      function.set_usage_counter(INT_MIN);
       return false;
     }
   }
   if (!function.IsOptimizable()) {
+    // Huge methods (code size above --huge_method_cutoff_in_code_size) become
+    // non-optimizable only after the code has been generated.
     if (FLAG_trace_failed_optimization_attempts) {
-      OS::PrintErr("Not Optimizable: %s\n", function.ToFullyQualifiedCString());
+      THR_Print("Not optimizable: %s\n", function.ToFullyQualifiedCString());
     }
-    // TODO(5442338): Abort as this should not happen.
-    function.set_usage_counter(kLowInvocationCount);
+    function.set_usage_counter(INT_MIN);
     return false;
   }
   return true;
 }
 
 
 DEFINE_RUNTIME_ENTRY(StackOverflow, 0) {
 #if defined(USING_SIMULATOR)
   uword stack_pos = Simulator::Current()->get_register(SPREG);
 #else
@@ skipping 579 matching lines @@
   const intptr_t elm_size = old_data.ElementSizeInBytes();
   const TypedData& new_data =
       TypedData::Handle(TypedData::New(cid, new_size, Heap::kOld));
   TypedData::Copy(new_data, 0, old_data, 0, old_size * elm_size);
   typed_data_cell.SetAt(0, new_data);
   arguments.SetReturn(new_data);
 }
 
 
 }  // namespace dart