Pass __class__ cell via a temporary __classcell__ attribute

Avoids false sharing of cells between contexts and gets closer to
CPython's behavior which also uses __classcell__.

Author: msimacek

graalpython/com.oracle.graal.python/src/com/oracle/graal/python/builtins/modules/BuiltinConstructors.java

@@ -52,6 +52,7 @@
 import static com.oracle.graal.python.nodes.BuiltinNames.TYPE;
 import static com.oracle.graal.python.nodes.BuiltinNames.ZIP;
 import static com.oracle.graal.python.nodes.SpecialAttributeNames.__BASICSIZE__;
+import static com.oracle.graal.python.nodes.SpecialAttributeNames.__CLASSCELL__;
 import static com.oracle.graal.python.nodes.SpecialAttributeNames.__DICTOFFSET__;
 import static com.oracle.graal.python.nodes.SpecialAttributeNames.__DICT__;
 import static com.oracle.graal.python.nodes.SpecialAttributeNames.__ITEMSIZE__;
@@ -2001,8 +2002,11 @@ Object type(VirtualFrame frame, LazyPythonClass cls, String name, PTuple bases,
                         @Cached GetLazyClassNode getMetaclassNode,
                         @Cached("create(__NEW__)") LookupInheritedAttributeNode getNewFuncNode,
                         @Cached("create(__INIT_SUBCLASS__)") GetAttributeNode getInitSubclassNode,
+                        @Cached HashingStorageNodes.GetItemNode getClasscellNode,
+                        @Cached HashingStorageNodes.DelItemNode delClasscellNode,
                         @Cached CallNode callInitSubclassNode,
                         @Cached CallNode callNewFuncNode) {
+
             // Determine the proper metatype to deal with this
             LazyPythonClass metaclass = calculate_metaclass(frame, cls, bases, getMetaclassNode);
             if (metaclass != cls) {
@@ -2038,6 +2042,17 @@ Object type(VirtualFrame frame, LazyPythonClass cls, String name, PTuple bases,
                     }
                 }
 
+                // set __class__ cell contents
+                Object classcell = getClasscellNode.execute(frame, namespace.getDictStorage(), __CLASSCELL__);
+                if (classcell != null) {
+                    if (classcell instanceof PCell) {
+                        ((PCell) classcell).setRef(newType);
+                    } else {
+                        raise(TypeError, "__classcell__ must be a cell");
+                    }
+                    delClasscellNode.execute(frame, namespace, namespace.getDictStorage(), __CLASSCELL__);
+                }
+
                 return newType;
             } catch (PException e) {
                 throw e;

graalpython/com.oracle.graal.python/src/com/oracle/graal/python/nodes/NodeFactory.java

@@ -36,7 +36,6 @@
 import com.oracle.graal.python.nodes.attributes.SetAttributeNode;
 import com.oracle.graal.python.nodes.call.PythonCallNode;
 import com.oracle.graal.python.nodes.cell.ReadLocalCellNode;
-import com.oracle.graal.python.nodes.cell.WriteCellVarNode;
 import com.oracle.graal.python.nodes.cell.WriteLocalCellNode;
 import com.oracle.graal.python.nodes.classes.ReadClassAttributeNode;
 import com.oracle.graal.python.nodes.control.BlockNode;
@@ -448,10 +447,6 @@ public ExpressionNode createReadClassAttributeNode(String identifier, FrameSlot
         return ReadClassAttributeNode.create(identifier, cellSlot, isFreeVar);
     }
 
-    public StatementNode createWriteCellVar(ExpressionNode readNode, FunctionRootNode funcRootNode, String identifier) {
-        return WriteCellVarNode.create(readNode, funcRootNode, identifier);
-    }
-
     public ExpressionNode createReadLocalCell(FrameSlot slot, boolean isFreeVar) {
         assert slot != null;
         return ReadLocalCellNode.create(slot, isFreeVar);

graalpython/com.oracle.graal.python/src/com/oracle/graal/python/nodes/SpecialAttributeNames.java

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2018, 2019, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2018, 2020, Oracle and/or its affiliates. All rights reserved.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
  * The Universal Permissive License (UPL), Version 1.0
@@ -45,6 +45,7 @@ public abstract class SpecialAttributeNames {
     public static final String __DEFAULTS__ = "__defaults__";
     public static final String __CODE__ = "__code__";
     public static final String __GLOBALS__ = "__globals__";
+    public static final String __CLASSCELL__ = "__classcell__";
     public static final String __CLOSURE__ = "__closure__";
     public static final String __ANNOTATIONS__ = "__annotations__";
     public static final String __KWDEFAULTS__ = "__kwdefaults__";

graalpython/com.oracle.graal.python/src/com/oracle/graal/python/nodes/cell/WriteCellVarNode.java

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2017, 2019, Oracle and/or its affiliates.
+ * Copyright (c) 2017, 2020, Oracle and/or its affiliates.
  * Copyright (c) 2013, Regents of the University of California
  *
  * All rights reserved.
@@ -54,7 +54,6 @@
  */
 public class FunctionRootNode extends PClosureFunctionRootNode {
     @CompilationFinal private ContextReference<PythonContext> contextRef;
-    private final PCell[] cells;
     private final ExecutionCellSlots executionCellSlots;
     private final String functionName;
     private final SourceSection sourceSection;
@@ -72,7 +71,6 @@ public FunctionRootNode(PythonLanguage language, SourceSection sourceSection, St
                     ExecutionCellSlots executionCellSlots, Signature signature) {
         super(language, frameDescriptor, executionCellSlots, signature);
         this.executionCellSlots = executionCellSlots;
-        this.cells = new PCell[this.cellVarSlots.length];
 
         this.sourceSection = sourceSection;
         assert sourceSection != null;
@@ -93,10 +91,6 @@ public String getName() {
         return functionName;
     }
 
-    public PCell[] getCells() {
-        return cells;
-    }
-
     public FrameSlot[] getCellVarSlots() {
         return cellVarSlots;
     }
@@ -123,7 +117,6 @@ private void initializeCellVars(Frame frame) {
 
             // store the cell as a local var
             frame.setObject(frameSlot, cell);
-            this.cells[i] = cell;
         }
     }
 

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

@@ -43,6 +43,7 @@
 
 import static com.oracle.graal.python.nodes.BuiltinNames.__BUILD_CLASS__;
 import static com.oracle.graal.python.nodes.SpecialAttributeNames.__ANNOTATIONS__;
+import static com.oracle.graal.python.nodes.SpecialAttributeNames.__CLASSCELL__;
 import static com.oracle.graal.python.nodes.SpecialAttributeNames.__CLASS__;
 import static com.oracle.graal.python.nodes.SpecialAttributeNames.__DOC__;
 import static com.oracle.graal.python.nodes.frame.FrameSlotIDs.TEMP_LOCAL_PREFIX;
@@ -388,7 +389,7 @@ public PNode visit(ClassSSTNode node) {
         classBody.assignSourceSection(createSourceSection(classBodyStart, node.body.endOffset));
 
         delta = delta + (classScope.hasAnnotations() ? 1 : 0);
-        StatementNode[] classStatements = new StatementNode[2 + delta];
+        StatementNode[] classStatements = new StatementNode[3 + delta];
         // ClassStatemtns look like:
         // [0] ClassDefinitionPrologueNode
         classStatements[0] = new ClassDefinitionPrologueNode(qualifiedName);
@@ -401,8 +402,11 @@ public PNode visit(ClassSSTNode node) {
         if (classScope.hasAnnotations()) {
             classStatements[delta] = scopeEnvironment.findVariable(__ANNOTATIONS__).makeWriteNode(nodeFactory.createDictLiteral());
         }
-        // [last] class body statements
+        // [last - 1] class body statements
         classStatements[1 + delta] = classBody;
+        // [last] assign __class__ cell to __classcell__
+        classStatements[2 + delta] = scopeEnvironment.findVariable(__CLASSCELL__).makeWriteNode(
+                        nodeFactory.createReadLocal(scopeEnvironment.getCurrentScope().getFrameDescriptor().findFrameSlot(__CLASS__)));
 
         SourceSection nodeSourceSection = createSourceSection(node.startOffset, node.endOffset);
         StatementNode body = nodeFactory.createBlock(classStatements);
@@ -439,11 +443,7 @@ public PNode visit(ClassSSTNode node) {
 
         ReadNode read = scopeEnvironment.findVariable(node.name);
 
-        ReadNode tempLocal = makeTempLocalVariable();
-        ExpressionNode newClass = ((ExpressionNode) tempLocal).withSideEffect(
-                        nodeFactory.createBlock(tempLocal.makeWriteNode(classDef),
-                                        nodeFactory.createWriteCellVar((ExpressionNode) tempLocal, classBodyRoot, __CLASS__)));
-        PNode result = read.makeWriteNode(newClass);
+        PNode result = read.makeWriteNode(classDef);
         result.assignSourceSection(nodeSourceSection);
         return result;
     }

graalpython/com.oracle.graal.python/src/com/oracle/graal/python/parser/sst/FactorySSTVisitor.java

@@ -389,7 +389,6 @@ graalpython/com.oracle.graal.python/src/com/oracle/graal/python/nodes/call/CallD
 graalpython/com.oracle.graal.python/src/com/oracle/graal/python/nodes/call/InvokeNode.java,zippy.copyright
 graalpython/com.oracle.graal.python/src/com/oracle/graal/python/nodes/call/PythonCallNode.java,zippy.copyright
 graalpython/com.oracle.graal.python/src/com/oracle/graal/python/nodes/cell/ReadLocalCellNode.java,zippy.copyright
-graalpython/com.oracle.graal.python/src/com/oracle/graal/python/nodes/cell/WriteCellVarNode.java,zippy.copyright
 graalpython/com.oracle.graal.python/src/com/oracle/graal/python/nodes/cell/WriteLocalCellNode.java,zippy.copyright
 graalpython/com.oracle.graal.python/src/com/oracle/graal/python/nodes/control/BaseBlockNode.java,zippy.copyright
 graalpython/com.oracle.graal.python/src/com/oracle/graal/python/nodes/control/BlockNode.java,zippy.copyright