--- a/mx.truffle/mx_truffle.py	Thu Nov 05 18:42:36 2015 +0100
+++ b/mx.truffle/mx_truffle.py	Thu Nov 12 11:35:19 2015 -0800
@@ -44,6 +44,11 @@
     vmArgs, slArgs = mx.extract_VM_args(args)
     mx.run_java(vmArgs + ['-cp', mx.classpath(["TRUFFLE_API", "com.oracle.truffle.sl"]), "com.oracle.truffle.sl.SLLanguage"] + slArgs)
 
+def slcoverage(args):
+    """Demo: run an SL program with coverage counts printed when done"""
+    vmArgs, slArgs = mx.extract_VM_args(args)
+    mx.run_java(vmArgs + ['-cp', mx.classpath("com.oracle.truffle.sl.tools"), "com.oracle.truffle.sl.tools.SLCoverage"] + slArgs)
+    
 def sldebug(args):
     """run a simple command line debugger for the Simple Language"""
     vmArgs, slArgs = mx.extract_VM_args(args, useDoubleDash=True)
@@ -58,4 +63,5 @@
 mx.update_commands(_suite, {
     'sl' : [sl, '[SL args|@VM options]'],
     'sldebug' : [sldebug, '[SL args|@VM options]'],
+    'slcoverage' : [slcoverage, '[SL args|@VM options]'],
 })

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/truffle/com.oracle.truffle.sl.tools/src/com/oracle/truffle/sl/tools/SLCoverage.java	Thu Nov 12 11:35:19 2015 -0800
@@ -0,0 +1,88 @@
+/*
+ * Copyright (c) 2015, 2015, 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
+ *
+ * Subject to the condition set forth below, permission is hereby granted to any
+ * person obtaining a copy of this software, associated documentation and/or
+ * data (collectively the "Software"), free of charge and under any and all
+ * copyright rights in the Software, and any and all patent rights owned or
+ * freely licensable by each licensor hereunder covering either (i) the
+ * unmodified Software as contributed to or provided by such licensor, or (ii)
+ * the Larger Works (as defined below), to deal in both
+ *
+ * (a) the Software, and
+ *
+ * (b) any piece of software and/or hardware listed in the lrgrwrks.txt file if
+ * one is included with the Software each a "Larger Work" to which the Software
+ * is contributed by such licensors),
+ *
+ * without restriction, including without limitation the rights to copy, create
+ * derivative works of, display, perform, and distribute the Software and make,
+ * use, sell, offer for sale, import, export, have made, and have sold the
+ * Software and the Larger Work(s), and to sublicense the foregoing rights on
+ * either these or other terms.
+ *
+ * This license is subject to the following condition:
+ *
+ * The above copyright notice and either this complete permission notice or at a
+ * minimum a reference to the UPL must be included in all copies or substantial
+ * portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+package com.oracle.truffle.sl.tools;
+
+import java.io.IOException;
+import java.lang.reflect.Field;
+
+import com.oracle.truffle.api.instrument.Instrumenter;
+import com.oracle.truffle.api.source.Source;
+import com.oracle.truffle.api.vm.PolyglotEngine;
+import com.oracle.truffle.api.vm.PolyglotEngine.Value;
+import com.oracle.truffle.tools.CoverageTracker;
+
+/**
+ * Temporary demonstration of code coverage counting.
+ * <p>
+ * This reflective access will become unnecessary when tool-related PolyglotEngine APIs are in
+ * place.
+ */
+public class SLCoverage {
+    public static void main(String[] args) throws IOException, NoSuchFieldException, SecurityException, IllegalArgumentException, IllegalAccessException {
+        PolyglotEngine vm = PolyglotEngine.newBuilder().build();
+        assert vm.getLanguages().containsKey("application/x-sl");
+        final Field field = PolyglotEngine.class.getDeclaredField("instrumenter");
+        field.setAccessible(true);
+        final Instrumenter instrumenter = (Instrumenter) field.get(vm);
+        final CoverageTracker coverageTracker = new CoverageTracker();
+        instrumenter.install(coverageTracker);
+
+        int repeats = 1;
+        if (args.length >= 2) {
+            repeats = Integer.parseInt(args[1]);
+        }
+
+        if (args.length == 0) {
+            throw new IOException("No SL source file specified.");
+        }
+        final Source source = Source.fromFileName(args[0]);
+
+        vm.eval(source);
+        Value main = vm.findGlobalSymbol("main");
+        if (main == null) {
+            throw new IOException("No function main() defined in SL source file.");
+        }
+        while (repeats-- > 0) {
+            main.invoke(null);
+        }
+        coverageTracker.print(System.out);
+    }
+}