--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/graal/GraalCompiler/src/com/sun/c1x/ir/NullCheck.java	Wed Apr 27 11:50:44 2011 +0200
@@ -0,0 +1,119 @@
+/*
+ * Copyright (c) 2009, 2011, 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.sun.c1x.ir;
+
+import com.sun.c1x.debug.*;
+import com.sun.c1x.util.*;
+import com.sun.c1x.value.*;
+import com.sun.cri.bytecode.*;
+import com.sun.cri.ri.*;
+
+/**
+ * The {@code NullCheck} class represents an explicit null check instruction.
+ *
+ * @author Ben L. Titzer
+ */
+public final class NullCheck extends StateSplit {
+
+    Value object;
+
+    /**
+     * Constructs a new NullCheck instruction.
+     * @param obj the instruction producing the object to check against null
+     * @param stateBefore the state before executing the null check
+     */
+    public NullCheck(Value obj, FrameState stateBefore) {
+        super(obj.kind, stateBefore);
+        this.object = obj;
+        setFlag(Flag.NonNull);
+        if (object.isNonNull()) {
+            eliminateNullCheck();
+        }
+    }
+
+    /**
+     * Gets the instruction that produces the object tested against null.
+     * @return the instruction producing the object
+     */
+    public Value object() {
+        return object;
+    }
+
+    /**
+     * Checks whether this instruction can cause a trap.
+     * @return {@code true} if this instruction can cause a trap
+     */
+    @Override
+    public boolean canTrap() {
+        return needsNullCheck();
+    }
+
+    @Override
+    public void inputValuesDo(ValueClosure closure) {
+        object = closure.apply(object);
+    }
+
+    @Override
+    public void accept(ValueVisitor v) {
+        v.visitNullCheck(this);
+    }
+
+    @Override
+    public int valueNumber() {
+        return Util.hash1(Bytecodes.IFNONNULL, object);
+    }
+
+    @Override
+    public boolean valueEqual(Instruction i) {
+        if (i instanceof NullCheck) {
+            NullCheck o = (NullCheck) i;
+            return object == o.object;
+        }
+        return false;
+    }
+
+    @Override
+    public RiType declaredType() {
+        // null check does not alter the type of the object
+        return object.declaredType();
+    }
+
+    @Override
+    public RiType exactType() {
+        // null check does not alter the type of the object
+        return object.exactType();
+    }
+
+    @Override
+    public void runtimeCheckCleared() {
+        clearState();
+    }
+
+    @Override
+    public void print(LogStream out) {
+        out.print("null_check(").print(object()).print(')');
+        if (!canTrap()) {
+          out.print(" (eliminated)");
+        }
+    }
+}