In-place shrinking of descriptor arrays with non-live transitions.

src/ic.cc

Index: src/ic.cc
diff --git a/src/ic.cc b/src/ic.cc
index 47a72b495636465761ce27fe4a0d97a107430f78..b189d07e4f4e8d27b1d129d60bc8d58d255c4cfa 100644
--- a/src/ic.cc
+++ b/src/ic.cc
@@ -1301,7 +1301,7 @@ void KeyedLoadIC::UpdateCaches(LookupResult* lookup,
 
 static bool StoreICableLookup(LookupResult* lookup) {
   // Bail out if we didn't find a result.
-  if (!lookup->IsFound() || lookup->type() == NULL_DESCRIPTOR) return false;
+  if (!lookup->IsFound()) return false;
 
   // Bail out if inline caching is not allowed.
   if (!lookup->IsCacheable()) return false;
@@ -1437,10 +1437,10 @@ void StoreIC::UpdateCaches(LookupResult* lookup,
                            Handle<Object> value) {
   ASSERT(!receiver->IsJSGlobalProxy());
   ASSERT(StoreICableLookup(lookup));
+  ASSERT(lookup->IsFound());
+
   // These are not cacheable, so we never see such LookupResults here.
   ASSERT(lookup->type() != HANDLER);
-  // We get only called for properties or transitions, see StoreICableLookup.
-  ASSERT(lookup->type() != NULL_DESCRIPTOR);
 
   // If the property has a non-field type allowing map transitions
   // where there is extra room in the object, we leave the IC in its
@@ -1512,8 +1512,8 @@ void StoreIC::UpdateCaches(LookupResult* lookup,
     case CONSTANT_FUNCTION:
     case CONSTANT_TRANSITION:
       return;
+    case NONEXISTENT:
     case HANDLER:
-    case NULL_DESCRIPTOR:
       UNREACHABLE();
       return;
   }
@@ -1939,10 +1939,9 @@ void KeyedStoreIC::UpdateCaches(LookupResult* lookup,
                                 Handle<Object> value) {
   ASSERT(!receiver->IsJSGlobalProxy());
   ASSERT(StoreICableLookup(lookup));
+  ASSERT(lookup->IsFound());

[Michael Starzinger, 2012/06/25 12:48:38]

Add an empty line so that it looks consistent with StoreIC::UpdateCaches.

   // These are not cacheable, so we never see such LookupResults here.
   ASSERT(lookup->type() != HANDLER);
-  // We get only called for properties or transitions, see StoreICableLookup.
-  ASSERT(lookup->type() != NULL_DESCRIPTOR);
 
   // If the property has a non-field type allowing map transitions
   // where there is extra room in the object, we leave the IC in its
@@ -1981,7 +1980,7 @@ void KeyedStoreIC::UpdateCaches(LookupResult* lookup,
           : generic_stub();
       break;
     case HANDLER:
-    case NULL_DESCRIPTOR:
+    case NONEXISTENT:
       UNREACHABLE();
       return;
   }