Generalize map dependent codes array to allow multiple dependency groups.

src/objects-inl.h

Index: src/objects-inl.h
diff --git a/src/objects-inl.h b/src/objects-inl.h
index 18894c1d56123f99fe02df5967ea06ffdac8a857..209c2ade04a077b1b340251f295bbfcbdd061e12 100644
--- a/src/objects-inl.h
+++ b/src/objects-inl.h
@@ -3425,44 +3425,64 @@ bool Map::is_observed() {
 }
 
 
-void Map::AddDependentCode(Handle<Code> code) {
+void Map::AddDependentCode(DependentCodes::DependencyGroup group,
+                           Handle<Code> code) {
   Handle<DependentCodes> codes =
-      DependentCodes::Append(Handle<DependentCodes>(dependent_codes()), code);
+      DependentCodes::Insert(Handle<DependentCodes>(dependent_codes()),
+                             group, code);
   if (*codes != dependent_codes()) {
     set_dependent_codes(*codes);
   }
 }
 
 
-int DependentCodes::number_of_codes() {
+int DependentCodes::number_of_codes(DependencyGroup group) {
   if (length() == 0) return 0;
-  return Smi::cast(get(kNumberOfCodesIndex))->value();
+  return Smi::cast(get(group))->value();
 }
 
 
-void DependentCodes::set_number_of_codes(int value) {
-  set(kNumberOfCodesIndex, Smi::FromInt(value));
+void DependentCodes::set_number_of_codes(DependencyGroup group, int value) {
+  set(group, Smi::FromInt(value));
 }
 
 
 Code* DependentCodes::code_at(int i) {
-  return Code::cast(get(kCodesIndex + i));
+  return Code::cast(get(kCodesStartIndex + i));
 }
 
 
 void DependentCodes::set_code_at(int i, Code* value) {
-  set(kCodesIndex + i, value);
+  set(kCodesStartIndex + i, value);
 }
 
 
 Object** DependentCodes::code_slot_at(int i) {
   return HeapObject::RawField(
-      this, FixedArray::OffsetOfElementAt(kCodesIndex + i));
+      this, FixedArray::OffsetOfElementAt(kCodesStartIndex + i));
 }
 
 
 void DependentCodes::clear_code_at(int i) {
-  set_undefined(kCodesIndex + i);
+  set_undefined(kCodesStartIndex + i);
+}
+
+
+void DependentCodes::ComputeGroupStartIndexes(GroupStartIndexes starts) {
+  starts[0] = 0;
+  for (int g = 1; g <= kGroupCount; g++) {
+    int count = number_of_codes(static_cast<DependencyGroup>(g - 1));
+    starts[g] = starts[g - 1] + count;
+  }
+}
+
+
+void DependentCodes::ExtendGroup(DependencyGroup group) {
+  GroupStartIndexes starts;
+  ComputeGroupStartIndexes(starts);
+  for (int g = kGroupCount - 2; g > group; g--) {
+    set_code_at(starts[g + 1], code_at(starts[g]));
+  }
 }