create an "incomplete" PFrame to make locals modifications work

Author: timfel

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

@@ -139,7 +139,6 @@
 import com.oracle.graal.python.nodes.expression.CastToBooleanNode;
 import com.oracle.graal.python.nodes.expression.TernaryArithmetic;
 import com.oracle.graal.python.nodes.frame.ReadCallerFrameNode;
-import com.oracle.graal.python.nodes.function.ClassBodyRootNode;
 import com.oracle.graal.python.nodes.function.FunctionRootNode;
 import com.oracle.graal.python.nodes.function.PythonBuiltinBaseNode;
 import com.oracle.graal.python.nodes.function.PythonBuiltinNode;
@@ -1613,22 +1612,16 @@ public Object globals(VirtualFrame frame) {
     abstract static class LocalsNode extends PythonBuiltinNode {
         @Child ReadCallerFrameNode readCallerFrameNode = ReadCallerFrameNode.create();
         private final ConditionProfile condProfile = ConditionProfile.createBinaryProfile();
-        private final ConditionProfile inClassProfile = ConditionProfile.createBinaryProfile();
 
         @Specialization
         public Object locals(VirtualFrame frame) {
             Frame callerFrame = readCallerFrameNode.executeWith(frame);
             PFrame pFrame = PArguments.getPFrame(callerFrame);
-            if (condProfile.profile(pFrame != null)) {
-                return pFrame.getLocals(factory());
-            } else {
-                Object specialArgument = PArguments.getSpecialArgument(callerFrame);
-                if (inClassProfile.profile(specialArgument instanceof ClassBodyRootNode)) {
-                    return factory().createDictLocals(callerFrame, true);
-                } else {
-                    return factory().createDictLocals(callerFrame, false);
-                }
+            if (condProfile.profile(pFrame == null)) {
+                pFrame = factory().createPFrame(callerFrame);
+                PArguments.setPFrame(callerFrame, pFrame);
             }
+            return pFrame.getLocals(factory());
         }
     }
 }

graalpython/com.oracle.graal.python/src/com/oracle/graal/python/builtins/objects/exception/PBaseException.java

@@ -209,7 +209,7 @@ public PFrame getPFrame(PythonObjectFactory factory, int index) {
         if (frame != null) {
             // we have a frame, try to get the pFrame from the magic arguments first
             pFrame = PArguments.getPFrame(frame);
-            if (pFrame == null) {
+            if (pFrame == null || pFrame.isIncomplete()) {
                 pFrame = factory.createPFrame(this, index);
                 PArguments.setPFrame(frame, pFrame);
             }

graalpython/com.oracle.graal.python/src/com/oracle/graal/python/builtins/objects/frame/PFrame.java

@@ -67,6 +67,15 @@ public final class PFrame extends PythonBuiltinObject {
     private final Node location;
     private int line = -2;
 
+    public PFrame(LazyPythonClass cls, Frame frame) {
+        super(cls);
+        this.exception = null;
+        this.index = -1;
+        this.frame = frame;
+        this.location = null;
+        this.inClassScope = PArguments.getSpecialArgument(frame) instanceof ClassBodyRootNode;
+    }
+
     public PFrame(LazyPythonClass cls, PBaseException exception, int index) {
         super(cls);
         this.exception = exception;
@@ -145,4 +154,13 @@ public PDict getLocals(PythonObjectFactory factory) {
         }
         return factory.createDict();
     }
+
+    /**
+     * Checks if this frame is complete in the sense that all frame accessors would work, e.g.
+     * locals, backref etc. We optimize locals access to create a lightweight PFrame that has no
+     * stack attached to it, which is where we check this.
+     */
+    public boolean isIncomplete() {
+        return location == null;
+    }
 }

graalpython/com.oracle.graal.python/src/com/oracle/graal/python/runtime/object/PythonObjectFactory.java

@@ -541,6 +541,10 @@ public PReferenceType createReferenceType(PythonObject object, PFunction callbac
      * Frames, traces and exceptions
      */
 
+    public PFrame createPFrame(Frame frame) {
+        return trace(new PFrame(PythonBuiltinClassType.PFrame, frame));
+    }
+
     public PFrame createPFrame(PBaseException exception, int index) {
         return trace(new PFrame(PythonBuiltinClassType.PFrame, exception, index));
     }