Trace CHA optimizations (where, when, why)

runtime/vm/flow_graph_optimizer.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/flow_graph_optimizer.h"
 
 #include "vm/bit_vector.h"
 #include "vm/cha.h"
 #include "vm/compiler.h"
 #include "vm/cpu.h"
@@ skipping 33 matching lines @@
 DEFINE_FLAG(bool, truncating_left_shift, true,
     "Optimize left shift to truncate if possible");
 DEFINE_FLAG(bool, use_cha_deopt, true,
     "Use class hierarchy analysis even if it can cause deoptimization.");
 #if defined(TARGET_ARCH_ARM) || defined(TARGET_ARCH_IA32)
 DEFINE_FLAG(bool, trace_smi_widening, false, "Trace Smi->Int32 widening pass.");
 #endif
 
 DECLARE_FLAG(bool, polymorphic_with_deopt);
 DECLARE_FLAG(bool, source_lines);
+DECLARE_FLAG(bool, trace_cha);
 DECLARE_FLAG(bool, trace_field_guards);
 DECLARE_FLAG(bool, trace_type_check_elimination);
 DECLARE_FLAG(bool, warn_on_javascript_compatibility);
 
 // Quick access to the current isolate and zone.
 #define I (isolate())
 #define Z (zone())
 
 static bool ShouldInlineSimd() {
   return FlowGraphCompiler::SupportsUnboxedSimd128();
@@ skipping 2264 matching lines @@
   ASSERT(callee_receiver != NULL);
   const Function& function = flow_graph_->function();
   if (function.IsDynamicFunction() &&
       callee_receiver->IsParameter() &&
       (callee_receiver->AsParameter()->index() == 0)) {
     const String& name = (kind == RawFunction::kMethodExtractor)
         ? String::Handle(Z, Field::NameFromGetter(call->function_name()))
         : call->function_name();
     const Class& cls = Class::Handle(Z, function.Owner());
     if (!thread()->cha()->HasOverride(cls, name)) {
+      if (FLAG_trace_cha) {
+        ISL_Print("  **(CHA) Instance call needs no check, "
+            "no overrides of '%s' '%s'\n",
+            name.ToCString(), cls.ToCString());
+      }
       thread()->cha()->AddToLeafClasses(cls);
       return false;
     }
   }
   return true;
 }
 
 
 bool FlowGraphOptimizer::InlineImplicitInstanceGetter(InstanceCallInstr* call,
                                                       bool allow_check) {
@@ skipping 1674 matching lines @@
   // Could be an interface check?
   if (CHA::IsImplemented(type_class)) return false;
   // Check if there are subclasses.
   if (CHA::HasSubclasses(type_class)) {
     return false;
   }
 
   // Private classes cannot be subclassed by later loaded libs.
   if (!type_class.IsPrivate()) {
     if (FLAG_use_cha_deopt) {
+      if (FLAG_trace_cha) {
+        ISL_Print("  **(CHA) Typecheck as class equality since no "
+            "subclasses: %s\n",
+            type_class.ToCString());
+      }
       thread()->cha()->AddToLeafClasses(type_class);
     } else {
       return false;
     }
   }
   const intptr_t num_type_args = type_class.NumTypeArguments();
   if (num_type_args > 0) {
     // Only raw types can be directly compared, thus disregarding type
     // arguments.
     const intptr_t num_type_params = type_class.NumTypeParameters();
@@ skipping 4729 matching lines @@
 
   // Insert materializations at environment uses.
   for (intptr_t i = 0; i < exits_collector_.exits().length(); i++) {
     CreateMaterializationAt(
         exits_collector_.exits()[i], alloc, *slots);
   }
 }
 
 
 }  // namespace dart