always peel the first iteration (like PyPy)

Author: timfel

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

@@ -185,7 +185,10 @@ public void executeVoid(VirtualFrame frame) {
         }
         frame.setObject(iteratorSlot, iterator.execute(frame));
         try {
-            loopNode.executeLoop(frame);
+            if (((ForRepeatingNode) loopNode.getRepeatingNode()).executeRepeating(frame)) {
+                // manually peel the first iteration
+                loopNode.executeLoop(frame);
+            }
         } finally {
             frame.setObject(iteratorSlot, null);
         }

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

@@ -81,6 +81,9 @@ public CastToBooleanNode getCondition() {
 
     @Override
     public void executeVoid(VirtualFrame frame) {
-        loopNode.executeLoop(frame);
+        if (((WhileRepeatingNode) loopNode.getRepeatingNode()).executeRepeating(frame)) {
+            // manually peel the first iteration
+            loopNode.executeLoop(frame);
+        }
     }
 }