--- a/graal/com.oracle.graal.compiler.test/src/com/oracle/graal/compiler/test/CheckGraalInvariants.java	Thu Mar 20 12:36:53 2014 +0100
+++ b/graal/com.oracle.graal.compiler.test/src/com/oracle/graal/compiler/test/CheckGraalInvariants.java	Thu Mar 20 12:37:43 2014 +0100
@@ -158,6 +158,7 @@
         new VerifyUsageWithEquals(JavaType.class).apply(graph, context);
         new VerifyUsageWithEquals(JavaMethod.class).apply(graph, context);
         new VerifyUsageWithEquals(JavaField.class).apply(graph, context);
+        new VerifyDebugUsage().apply(graph, context);
     }
 
     private static boolean matches(String[] filters, String s) {

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/graal/com.oracle.graal.phases/src/com/oracle/graal/phases/verify/VerifyDebugUsage.java	Thu Mar 20 12:37:43 2014 +0100
@@ -0,0 +1,73 @@
+/*
+ * Copyright (c) 2013, Oracle and/or its affiliates. All rights reserved.
+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
+ *
+ * This code is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 only, as
+ * published by the Free Software Foundation.
+ *
+ * This code is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+ * version 2 for more details (a copy is included in the LICENSE file that
+ * accompanied this code).
+ *
+ * You should have received a copy of the GNU General Public License version
+ * 2 along with this work; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
+ * or visit www.oracle.com if you need additional information or have any
+ * questions.
+ */
+package com.oracle.graal.phases.verify;
+
+import static com.oracle.graal.api.meta.MetaUtil.*;
+
+import com.oracle.graal.api.meta.*;
+import com.oracle.graal.debug.*;
+import com.oracle.graal.nodes.*;
+import com.oracle.graal.nodes.java.*;
+import com.oracle.graal.phases.*;
+import com.oracle.graal.phases.tiers.*;
+
+/**
+ * Verifies that no argument to one of the {@link Debug#log(String)} methods is the result of
+ * {@link StringBuilder#toString()} or {@link StringBuffer#toString()}. Instead, one of the
+ * multi-parameter {@code log()} methods should be used. The goal is to minimize/prevent allocation
+ * at logging call sites.
+ */
+public class VerifyDebugUsage extends VerifyPhase<PhaseContext> {
+
+    @Override
+    protected boolean verify(StructuredGraph graph, PhaseContext context) {
+        for (MethodCallTargetNode t : graph.getNodes(MethodCallTargetNode.class)) {
+            ResolvedJavaMethod callee = t.targetMethod();
+            ResolvedJavaType debugType = context.getMetaAccess().lookupJavaType(Debug.class);
+            if (callee.getDeclaringClass().equals(debugType)) {
+                if (callee.getName().equals("log")) {
+                    int argIdx = 1;
+                    for (ValueNode arg : t.arguments()) {
+                        if (arg instanceof Invoke) {
+                            Invoke invoke = (Invoke) arg;
+                            CallTargetNode callTarget = invoke.callTarget();
+                            if (callTarget instanceof MethodCallTargetNode) {
+                                ResolvedJavaMethod m = ((MethodCallTargetNode) callTarget).targetMethod();
+                                if (m.getName().equals("toString")) {
+                                    String holder = m.getDeclaringClass().getName();
+                                    if (holder.equals("Ljava/lang/StringBuilder;") || holder.equals("Ljava/lang/StringBuffer;")) {
+                                        StackTraceElement e = graph.method().asStackTraceElement(invoke.bci());
+                                        throw new VerificationError(String.format("%s: parameter %d of call to %s appears to be a String concatenation expression.%n"
+                                                        + "    Use one of the multi-parameter Debug.log() methods of Debug.logv() instead.", e, argIdx, format("%H.%n(%p)", callee)));
+                                    }
+                                }
+                            }
+                        }
+                        argIdx++;
+                    }
+                }
+            }
+        }
+        return true;
+    }
+}