Try to optimise marking for common cases.

Author: aardvark179

src/main/java/org/truffleruby/core/MarkingService.java

@@ -42,12 +42,14 @@ public static interface MarkerAction {
     protected static class ExtensionCallStackEntry {
 
         protected final ExtensionCallStackEntry previous;
+        protected ValueWrapper preservedObject;
         protected ArrayList<ValueWrapper> preservedObjects;
         protected final boolean keywordsGiven;
         protected Object specialVariables;
         protected final Object block;
         protected CapturedException capturedException;
-        protected ArrayList<ValueWrapper> forMarking;
+        protected ValueWrapper markOnExitObject;
+        protected ArrayList<ValueWrapper> markOnExitObjects;
         protected Object[] marks;
         protected int marksIndex = 0;
 
@@ -73,7 +75,24 @@ public ExtensionCallStack(Object specialVariables, Object block) {
         }
 
         public boolean hasKeptObjects() {
-            return current.preservedObjects != null;
+            return current.preservedObject != null;
+        }
+
+        public void keepObject(ValueWrapper value) {
+            if (current.preservedObject == null) {
+                current.preservedObject = value;
+            } else {
+                keepObjectOnList(value);
+            }
+        }
+
+        @TruffleBoundary
+        private void keepObjectOnList(ValueWrapper value) {
+            if (current.preservedObjects == null) {
+                current.preservedObjects = new ArrayList<>();
+                current.preservedObjects.add(current.preservedObject);
+            }
+            current.preservedObjects.add(value);
         }
 
         public ArrayList<ValueWrapper> getKeptObjects() {
@@ -85,17 +104,42 @@ public ArrayList<ValueWrapper> getKeptObjects() {
             return current.preservedObjects;
         }
 
+        public void markOnExitObject(ValueWrapper value) {
+            if (current.markOnExitObject == null) {
+                current.markOnExitObject = value;
+            } else {
+                markOnExitObjectOnList(value);
+            }
+        }
+
+        @TruffleBoundary
+        private void markOnExitObjectOnList(ValueWrapper value) {
+            if (current.markOnExitObjects == null) {
+                current.markOnExitObjects = new ArrayList<>();
+                current.markOnExitObjects.add(current.markOnExitObject);
+            }
+            current.markOnExitObjects.add(value);
+        }
+
         public ArrayList<ValueWrapper> getMarkOnExitObjects() {
             assert current.previous != null;
 
-            if (current.forMarking == null) {
-                current.forMarking = new ArrayList<>();
+            if (current.markOnExitObjects == null) {
+                current.markOnExitObjects = new ArrayList<>();
             }
-            return current.forMarking;
+            return current.markOnExitObjects;
         }
 
         public boolean hasMarkObjects() {
-            return current.forMarking != null;
+            return current.markOnExitObject != null;
+        }
+
+        public boolean hasSingleMarkObject() {
+            return current.markOnExitObject != null && current.markOnExitObjects == null;
+        }
+
+        public ValueWrapper getSingleMarkObject() {
+            return current.markOnExitObject;
         }
 
         public void pop() {
@@ -135,7 +179,7 @@ public void startMarking(ExtensionCallStack stack, Object[] oldMarks) {
         if (oldMarks == null) {
             stack.current.marks = ArrayUtils.EMPTY_ARRAY;
         } else {
-            stack.current.marks = new Object[oldMarks.length];
+            stack.current.marks = oldMarks;
         }
         stack.current.marksIndex = 0;
     }

src/main/java/org/truffleruby/core/MarkingServiceNodes.java

@@ -26,9 +26,8 @@ public void execute(ValueWrapper object) {
             addToList(getLanguage().getCurrentThread().getCurrentFiber().extensionCallStack, object);
         }
 
-        @TruffleBoundary
         protected void addToList(ExtensionCallStack stack, ValueWrapper object) {
-            stack.getKeptObjects().add(object);
+            stack.keepObject(object);
         }
 
         public static KeepAliveNode create() {
@@ -46,9 +45,8 @@ public void execute(ValueWrapper object) {
             addToList(getLanguage().getCurrentThread().getCurrentFiber().extensionCallStack, object);
         }
 
-        @TruffleBoundary
         protected void addToList(ExtensionCallStack stack, ValueWrapper object) {
-            stack.getMarkOnExitObjects().add(object);
+            stack.markOnExitObject(object);
         }
 
         public static QueueForMarkOnExitNode create() {
@@ -65,8 +63,15 @@ protected void nothingToMark(ExtensionCallStack stack) {
             // Do nothing.
         }
 
+        @Specialization(guards = "stack.hasSingleMarkObject()")
+        protected void markSingleObject(ExtensionCallStack stack,
+                @Cached DispatchNode callNode) {
+            ValueWrapper value = stack.getSingleMarkObject();
+            callNode.call(getContext().getCoreLibrary().truffleCExtModule, "run_marker", value.getObject());
+        }
+
         @TruffleBoundary
-        @Specialization(guards = "stack.hasMarkObjects()")
+        @Specialization(guards = { "stack.hasMarkObjects()", "!stack.hasSingleMarkObject()" })
         protected void marksToRun(ExtensionCallStack stack,
                 @Cached DispatchNode callNode) {
             // Run the markers...