When marking dependent code for deoptimization print the group that is being deoptimized.

src/objects.cc

 // Copyright 2013 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "src/v8.h"
 
 #include "src/accessors.h"
 #include "src/allocation-site-scopes.h"
 #include "src/api.h"
 #include "src/arguments.h"
@@ skipping 11768 matching lines @@
   int end = starts.at(group + 1);
   int code_entries = starts.number_of_entries();
   if (start == end) return false;
 
   // Mark all the code that needs to be deoptimized.
   bool marked = false;
   for (int i = start; i < end; i++) {
     if (is_code_at(i)) {
       Code* code = code_at(i);
       if (!code->marked_for_deoptimization()) {
-        code->set_marked_for_deoptimization(true);
+        SetMarkedForDeoptimization(code, group);
         marked = true;
       }
     } else {
       CompilationInfo* info = compilation_info_at(i);
       info->AbortDueToDependencyChange();
     }
   }
   // Compact the array by moving all subsequent groups to fill in the new holes.
   for (int src = end, dst = start; src < code_entries; src++, dst++) {
     copy(src, dst);
@@ skipping 30 matching lines @@
   if (head->IsCode()) {
     stub->set_next_code_link(Code::cast(head)->next_code_link());
     Code::cast(head)->set_next_code_link(*stub);
   } else {
     stub->set_next_code_link(head);
     set_object_at(i, *stub);
   }
 }
 
 
+void DependentCode::SetMarkedForDeoptimization(Code* code,
+                                               DependencyGroup group) {
+  code->set_marked_for_deoptimization(true);
+  if (FLAG_trace_deopt &&
+      (code->deoptimization_data() != code->GetHeap()->empty_fixed_array())) {
+    DeoptimizationInputData* deopt_data =
+        DeoptimizationInputData::cast(code->deoptimization_data());
+    CodeTracer::Scope scope(code->GetHeap()->isolate()->GetCodeTracer());
+    PrintF(scope.file(), "[marking dependent code 0x%08" V8PRIxPTR
+                         " (opt #%d) for deoptimization, reason: %s]\n",
+           reinterpret_cast<intptr_t>(code),
+           deopt_data->OptimizationId()->value(), DependencyGroupName(group));
+  }
+}
+
+
+const char* DependentCode::DependencyGroupName(DependencyGroup group) {
+  switch (group) {
+    case kWeakICGroup:
+      return "weak-ic";
+    case kWeakCodeGroup:
+      return "weak-code";
+    case kTransitionGroup:
+      return "transition";
+    case kPrototypeCheckGroup:
+      return "prototype-check";
+    case kElementsCantBeAddedGroup:
+      return "elements-cant-be-added";
+    case kPropertyCellChangedGroup:
+      return "property-cell-changed";
+    case kFieldTypeGroup:
+      return "field-type";
+    case kInitialMapChangedGroup:
+      return "initial-map-changed";
+    case kAllocationSiteTenuringChangedGroup:
+      return "allocation-site-tenuring-changed";
+    case kAllocationSiteTransitionChangedGroup:
+      return "allocation-site-transition-changed";
+    default:

[Toon Verwaest, 2014/08/19 11:08:04]

Any reason why you added a default case? That kinda ensures we'll definitely
forget to update this list when we add a new case.

[Vyacheslav Egorov (Google), 2014/08/19 11:14:41]

Well, main reason is that enumeration has parasitic kGroupCount right now.

Right way would be to move kGroupCount out and then I could kill default: case
here, because I do agree - it's nice to not have it, and get a warning for
uncovered cases.

If you want I can submit a follow up CL for this.

+      UNREACHABLE();
+      return "?";
+  }
+}
+
+
 Handle<Map> Map::TransitionToPrototype(Handle<Map> map,
                                        Handle<Object> prototype) {
   Handle<Map> new_map = GetPrototypeTransition(map, prototype);
   if (new_map.is_null()) {
     new_map = Copy(map);
     PutPrototypeTransition(map, prototype, new_map);
     new_map->set_prototype(*prototype);
   }
   return new_map;
 }
@@ skipping 4764 matching lines @@
 #define ERROR_MESSAGES_TEXTS(C, T) T,
   static const char* error_messages_[] = {
       ERROR_MESSAGES_LIST(ERROR_MESSAGES_TEXTS)
   };
 #undef ERROR_MESSAGES_TEXTS
   return error_messages_[reason];
 }
 
 
 } }  // namespace v8::internal