retain a strong root to a class' final storage shape

Author: lukasstadler

graalpython/com.oracle.graal.python/src/com/oracle/graal/python/builtins/objects/common/DynamicObjectStorage.java

@@ -109,6 +109,10 @@ public DynamicObjectStorage(DynamicObject store, MroSequenceStorage mro) {
         this.mro = mro;
     }
 
+    public Shape getStoreShape() {
+        return store.getShape();
+    }
+
     protected static Object[] keyArray(DynamicObjectStorage self) {
         return DynamicObjectStorage.keyArray(self.store.getShape());
     }

graalpython/com.oracle.graal.python/src/com/oracle/graal/python/nodes/function/ClassBodyRootNode.java

@@ -41,11 +41,17 @@
 package com.oracle.graal.python.nodes.function;
 
 import com.oracle.graal.python.PythonLanguage;
+import com.oracle.graal.python.builtins.objects.common.DynamicObjectStorage;
+import com.oracle.graal.python.builtins.objects.dict.PDict;
+import com.oracle.graal.python.builtins.objects.function.PArguments;
 import com.oracle.graal.python.builtins.objects.function.Signature;
 import com.oracle.graal.python.nodes.expression.ExpressionNode;
 import com.oracle.graal.python.parser.ExecutionCellSlots;
 import com.oracle.graal.python.util.PythonUtils;
+import com.oracle.truffle.api.CompilerDirectives;
+import com.oracle.truffle.api.CompilerDirectives.CompilationFinal;
 import com.oracle.truffle.api.frame.FrameDescriptor;
+import com.oracle.truffle.api.frame.VirtualFrame;
 import com.oracle.truffle.api.source.SourceSection;
 
 public class ClassBodyRootNode extends FunctionRootNode {
@@ -54,4 +60,30 @@ public class ClassBodyRootNode extends FunctionRootNode {
     public ClassBodyRootNode(PythonLanguage language, SourceSection sourceSection, String functionName, FrameDescriptor frameDescriptor, ExpressionNode body, ExecutionCellSlots executionCellSlots) {
         super(language, sourceSection, functionName, false, false, frameDescriptor, body, executionCellSlots, SIGNATURE, null);
     }
+
+    /**
+     * Used to keep the shape hierarchy of the objects created in this class body alive.
+     */
+    @CompilationFinal private Object cachedShape;
+
+    private static final Object NO_CACHED_SHAPE = "<none>";
+
+    @Override
+    public Object execute(VirtualFrame frame) {
+        try {
+            return super.execute(frame);
+        } finally {
+            if (cachedShape == null) {
+                CompilerDirectives.transferToInterpreterAndInvalidate();
+                cachedShape = NO_CACHED_SHAPE;
+                Object arg = PArguments.getArgument(frame, 0);
+                if (arg instanceof PDict) {
+                    Object storage = ((PDict) arg).getDictStorage();
+                    if (storage instanceof DynamicObjectStorage) {
+                        cachedShape = ((DynamicObjectStorage) storage).getStoreShape();
+                    }
+                }
+            }
+        }
+    }
 }