Add 'terminating return' optimization for interpreter performance

Adds additional execute method to the StatementNode. This method is
allowed perform Python level return via Java level return. This can be
safely done only for the last statement given normal structured
control flow without any jumps.

Author: steve-s

graalpython/com.oracle.graal.python/src/com/oracle/graal/python/nodes/control/BaseBlockNode.java

@@ -27,8 +27,11 @@
 
 import java.util.List;
 
+import com.oracle.graal.python.builtins.objects.PNone;
 import com.oracle.graal.python.nodes.statement.StatementNode;
 import com.oracle.graal.python.util.PythonUtils;
+import com.oracle.truffle.api.frame.VirtualFrame;
+import com.oracle.truffle.api.nodes.ExplodeLoop;
 
 public abstract class BaseBlockNode extends StatementNode {
 
@@ -66,4 +69,25 @@ protected StatementNode[] insertStatementsBefore(StatementNode insertBefore, Lis
     public final StatementNode[] getStatements() {
         return statements;
     }
+
+    @Override
+    @ExplodeLoop
+    public void executeVoid(VirtualFrame frame) {
+        for (int i = 0; i < statements.length; i++) {
+            statements[i].executeVoid(frame);
+        }
+    }
+
+    @Override
+    @ExplodeLoop
+    public Object returnExecute(VirtualFrame frame) {
+        for (int i = 0; i < statements.length - 1; i++) {
+            statements[i].executeVoid(frame);
+        }
+        if (statements.length > 0) {
+            return statements[statements.length - 1].returnExecute(frame);
+        } else {
+            return PNone.NONE;
+        }
+    }
 }

graalpython/com.oracle.graal.python/src/com/oracle/graal/python/nodes/control/BlockNode.java

@@ -26,8 +26,6 @@
 package com.oracle.graal.python.nodes.control;
 
 import com.oracle.graal.python.nodes.statement.StatementNode;
-import com.oracle.truffle.api.frame.VirtualFrame;
-import com.oracle.truffle.api.nodes.ExplodeLoop;
 
 public final class BlockNode extends BaseBlockNode {
 
@@ -46,12 +44,4 @@ public static StatementNode create(StatementNode... statements) {
             return new BlockNode(statements);
         }
     }
-
-    @Override
-    @ExplodeLoop
-    public void executeVoid(VirtualFrame frame) {
-        for (int i = 0; i < statements.length; i++) {
-            statements[i].executeVoid(frame);
-        }
-    }
 }

graalpython/com.oracle.graal.python/src/com/oracle/graal/python/nodes/control/ReturnNode.java

@@ -25,7 +25,11 @@
  */
 package com.oracle.graal.python.nodes.control;
 
+import com.oracle.graal.python.builtins.objects.PNone;
 import com.oracle.graal.python.nodes.PNode;
+import com.oracle.graal.python.nodes.frame.WriteFrameSlotNode;
+import com.oracle.graal.python.nodes.expression.ExpressionNode;
+import com.oracle.graal.python.nodes.frame.WriteIdentifierNode;
 import com.oracle.graal.python.nodes.statement.StatementNode;
 import com.oracle.graal.python.runtime.exception.ReturnException;
 import com.oracle.truffle.api.frame.VirtualFrame;
@@ -37,6 +41,11 @@ public void executeVoid(VirtualFrame frame) {
         throw ReturnException.INSTANCE;
     }
 
+    @Override
+    public Object returnExecute(VirtualFrame frame) {
+        return PNone.NONE;
+    }
+
     public static final class FrameReturnNode extends ReturnNode {
         @Child private StatementNode right;
 
@@ -53,5 +62,10 @@ public void executeVoid(VirtualFrame frame) {
             right.executeVoid(frame);
             throw ReturnException.INSTANCE;
         }
+
+        @Override
+        public Object returnExecute(VirtualFrame frame) {
+            return right.getRhs().execute(frame);
+        }
     }
 }

graalpython/com.oracle.graal.python/src/com/oracle/graal/python/nodes/control/ReturnTargetNode.java

@@ -55,12 +55,11 @@ public ExpressionNode getReturn() {
     @Override
     public Object execute(VirtualFrame frame) {
         try {
-            body.executeVoid(frame);
-            fallthroughProfile.enter();
-            return PNone.NONE;
+            return body.returnExecute(frame);
         } catch (ReturnException ire) {
-            returnProfile.enter();
-            return returnValue.execute(frame);
+            // fall-though
         }
+        returnProfile.enter();
+        return returnValue.execute(frame);
     }
 }

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

@@ -42,10 +42,8 @@
 
 import com.oracle.graal.python.nodes.control.BaseBlockNode;
 import com.oracle.graal.python.nodes.statement.StatementNode;
-import com.oracle.truffle.api.frame.VirtualFrame;
 import com.oracle.truffle.api.instrumentation.StandardTags;
 import com.oracle.truffle.api.instrumentation.Tag;
-import com.oracle.truffle.api.nodes.ExplodeLoop;
 
 public class FunctionBodyNode extends BaseBlockNode {
 
@@ -57,14 +55,6 @@ public static FunctionBodyNode create(StatementNode... statements) {
         return statements.length == 0 ? new FunctionBodyNode(new StatementNode[0]) : new FunctionBodyNode(statements);
     }
 
-    @Override
-    @ExplodeLoop
-    public void executeVoid(VirtualFrame frame) {
-        for (int i = 0; i < statements.length; i++) {
-            statements[i].executeVoid(frame);
-        }
-    }
-
     @Override
     public boolean hasTag(Class<? extends Tag> tag) {
         return StandardTags.RootBodyTag.class == tag;

graalpython/com.oracle.graal.python/src/com/oracle/graal/python/nodes/generator/GeneratorBlockNode.java

@@ -25,6 +25,7 @@
  */
 package com.oracle.graal.python.nodes.generator;
 
+import com.oracle.graal.python.builtins.objects.PNone;
 import com.oracle.graal.python.nodes.control.BaseBlockNode;
 import com.oracle.graal.python.nodes.statement.StatementNode;
 import com.oracle.graal.python.parser.GeneratorInfo;

graalpython/com.oracle.graal.python/src/com/oracle/graal/python/nodes/statement/StatementNode.java

@@ -25,6 +25,7 @@
  */
 package com.oracle.graal.python.nodes.statement;
 
+import com.oracle.graal.python.builtins.objects.PNone;
 import com.oracle.graal.python.nodes.PNode;
 import com.oracle.truffle.api.CompilerDirectives.CompilationFinal;
 import com.oracle.truffle.api.frame.VirtualFrame;
@@ -42,6 +43,16 @@ public abstract class StatementNode extends PNode {
 
     public abstract void executeVoid(VirtualFrame frame);
 
+    /**
+     * Execution can directly return the value from return statement if it is the last statement
+     * that was executed. This method may still throw
+     * {@link com.oracle.graal.python.runtime.exception.ReturnException}.
+     */
+    public Object returnExecute(VirtualFrame frame) {
+        executeVoid(frame);
+        return PNone.NONE;
+    }
+
     public void markAsTryBlock() {
         isTryBlock = true;
     }
@@ -50,6 +61,7 @@ public boolean isTryBlock() {
         return isTryBlock;
     }
 
+    @Override
     public WrapperNode createWrapper(ProbeNode probe) {
         return new StatementNodeWrapper(this, probe);
     }