Use kIllegalObjectKind instead of NULL object to terminate ICData array

runtime/vm/object.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/object.h"
 
 #include "platform/assert.h"
 #include "vm/assembler.h"
 #include "vm/bigint_operations.h"
 #include "vm/bootstrap.h"
@@ skipping 7194 matching lines @@
   return num_args_tested() + 1 /* target function*/;
 }
 
 
 intptr_t ICData::NumberOfChecks() const {
   // Do not count the sentinel;
   return (Array::Handle(ic_data()).Length() / TestEntryLength()) - 1;
 }
 
 
+void ICData::WriteSentinel() const {
+  const Smi& sentinel_value = Smi::Handle(Smi::New(kIllegalObjectKind));
+  const Array& data = Array::Handle(ic_data());
+  for (intptr_t i = 1; i <= TestEntryLength(); i++) {
+    data.SetAt(data.Length() - i, sentinel_value);
+  }
+}
+
+
 void ICData::AddCheck(const GrowableArray<intptr_t>& class_ids,
                       const Function& target) const {
   ASSERT(num_args_tested() > 1);  // Otherwise use 'AddReceiverCheck'.
   ASSERT(class_ids.length() == num_args_tested());
-  intptr_t old_num = NumberOfChecks();
+  const intptr_t old_num = NumberOfChecks();
   Array& data = Array::Handle(ic_data());
-  intptr_t new_len = data.Length() + TestEntryLength();
+  const intptr_t new_len = data.Length() + TestEntryLength();
   data = Array::Grow(data, new_len, Heap::kOld);
   set_ic_data(data);
+  WriteSentinel();
   intptr_t data_pos = old_num * TestEntryLength();
   for (intptr_t i = 0; i < class_ids.length(); i++) {
-    // Null is used as terminating value, do not add it.
-    ASSERT(class_ids[i] != kNullClass);
+    // kIllegalObjectKind is used as terminating value, do not add it.
     ASSERT(class_ids[i] != kIllegalObjectKind);
     data.SetAt(data_pos++, Smi::Handle(Smi::New(class_ids[i])));
   }
   ASSERT(!target.IsNull());
   data.SetAt(data_pos, target);
 }
 
 
 void ICData::AddReceiverCheck(intptr_t receiver_class_id,
                               const Function& target) const {
   ASSERT(num_args_tested() == 1);  // Otherwise use 'AddCheck'.
-  // Not supporting collection of null receivers.
-  ASSERT(receiver_class_id != kNullClass);
   ASSERT(receiver_class_id != kIllegalObjectKind);
   ASSERT(!target.IsNull());
 
-  intptr_t old_num = NumberOfChecks();
+  const intptr_t old_num = NumberOfChecks();
   Array& data = Array::Handle(ic_data());
-  intptr_t new_len = data.Length() + TestEntryLength();
+  const intptr_t new_len = data.Length() + TestEntryLength();
   data = Array::Grow(data, new_len, Heap::kOld);
   set_ic_data(data);
+  WriteSentinel();
   intptr_t data_pos = old_num * TestEntryLength();
   if ((receiver_class_id == kSmi) && (data_pos > 0)) {
     // Instert kSmi in position 0.
     const intptr_t zero_class_id = GetReceiverClassIdAt(0);
     ASSERT(zero_class_id != kSmi);  // Simple duplicate entry check.
     const Function& zero_target = Function::Handle(GetTargetAt(0));
     data.SetAt(0, Smi::Handle(Smi::New(receiver_class_id)));
     data.SetAt(1, target);
     data.SetAt(data_pos, Smi::Handle(Smi::New(zero_class_id)));
     data.SetAt(data_pos + 1, zero_target);
@@ skipping 112 matching lines @@
   }
   result.set_function(function);
   result.set_target_name(target_name);
   result.set_id(id);
   result.set_num_args_tested(num_args_tested);
   // Number of array elements in one test entry (num_args_tested + 1)
   intptr_t len = result.TestEntryLength();
   // IC data array must be null terminated (sentinel entry).
   const Array& ic_data = Array::Handle(Array::New(len, Heap::kOld));
   result.set_ic_data(ic_data);
+  result.WriteSentinel();
   return result.raw();
 }
 
 
 RawSubtypeTestCache* SubtypeTestCache::New() {
   ASSERT(Object::subtypetestcache_class() != Class::null());
   SubtypeTestCache& result = SubtypeTestCache::Handle();
   {
     // SubtypeTestCache objects are long living objects, allocate them in the
     // old generation.
@@ skipping 3370 matching lines @@
   const String& str = String::Handle(pattern());
   const char* format = "JSRegExp: pattern=%s flags=%s";
   intptr_t len = OS::SNPrint(NULL, 0, format, str.ToCString(), Flags());
   char* chars = reinterpret_cast<char*>(
       Isolate::Current()->current_zone()->Allocate(len + 1));
   OS::SNPrint(chars, (len + 1), format, str.ToCString(), Flags());
   return chars;
 }
 
 }  // namespace dart