Zap holes in dependent code array after deoptimizing a code group.

src/objects.cc

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 9583 matching lines @@
   AssertNoAllocation no_allocation_scope;
   DependentCode::GroupStartIndexes starts(this);
   int start = starts.at(group);
   int end = starts.at(group + 1);
   int number_of_entries = starts.at(DependentCode::kGroupCount);
   if (start == end) return;
   for (int i = start; i < end; i++) {
     Code* code = code_at(i);
     code->set_marked_for_deoptimization(true);
   }
+  // Compact the array by moving all subsequent groups to fill in the new holes.
   for (int src = end, dst = start; src < number_of_entries; src++, dst++) {
     set_code_at(dst, code_at(src));
   }
+  // Now the holes are at the end of the array, zap them.

[Michael Starzinger, 2013/02/25 12:18:22]

Maybe we should add a comment saying that this is only needed by the
heap-verifier, but we play it safe and always do it. I'll leave this up to you.

+  int removed = end - start;
+  for (int i = number_of_entries - removed; i < number_of_entries; i++) {
+    clear_code_at(i);
+  }
   set_number_of_entries(group, 0);
   DeoptimizeDependentCodeFilter filter;
   Deoptimizer::DeoptimizeAllFunctionsWith(&filter);
 }
 
 
 MaybeObject* JSReceiver::SetPrototype(Object* value,
                                       bool skip_hidden_prototypes) {
 #ifdef DEBUG
   int size = Size();
@@ skipping 4367 matching lines @@
   set_year(Smi::FromInt(year), SKIP_WRITE_BARRIER);
   set_month(Smi::FromInt(month), SKIP_WRITE_BARRIER);
   set_day(Smi::FromInt(day), SKIP_WRITE_BARRIER);
   set_weekday(Smi::FromInt(weekday), SKIP_WRITE_BARRIER);
   set_hour(Smi::FromInt(hour), SKIP_WRITE_BARRIER);
   set_min(Smi::FromInt(min), SKIP_WRITE_BARRIER);
   set_sec(Smi::FromInt(sec), SKIP_WRITE_BARRIER);
 }
 
 } }  // namespace v8::internal