--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/graal/Compiler/src/com/sun/c1x/opt/InstructionSubstituter.java	Wed Apr 27 11:43:22 2011 +0200
@@ -0,0 +1,99 @@
+/*
+ * 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.opt;
+
+import com.sun.c1x.ir.*;
+import com.sun.c1x.value.*;
+import com.sun.c1x.graph.IR;
+
+/**
+ * This class allows instructions to be substituted within an IR graph. It allows
+ * registering substitutions and iterates over the instructions of a program and replaces
+ * the occurrence of each instruction with its substitution, if it has one.
+ *
+ * @author Ben L. Titzer
+ */
+public final class InstructionSubstituter implements BlockClosure, ValueClosure {
+
+    final IR ir;
+    boolean hasSubstitution;
+
+    public InstructionSubstituter(IR ir) {
+        this.ir = ir;
+    }
+
+    public void apply(BlockBegin block) {
+        Instruction last = null;
+        if (block.exceptionHandlerStates() != null) {
+            for (FrameState s : block.exceptionHandlerStates()) {
+                s.valuesDo(this);
+            }
+        }
+        for (Instruction n = block; n != null; n = last.next()) {
+            n.allValuesDo(this);
+            if (n.subst != null && last != null) {
+                // this instruction has a substitution, skip it
+                last.resetNext(n.next());
+            } else {
+                last = n;
+            }
+        }
+    }
+
+    public void finish() {
+        if (hasSubstitution) {
+            ir.startBlock.iterateAnyOrder(this, false);
+        }
+    }
+
+    public boolean hasSubst(Value i) {
+        return i.subst != null;
+    }
+
+    public void setSubst(Value i, Value n) {
+        if (i == n) {
+            i.subst = null;
+        } else {
+            hasSubstitution = true;
+            i.subst = n;
+        }
+    }
+
+    public Value getSubst(Value i) {
+        Value p = i;
+        while (true) {
+            if (p.subst == null) {
+                break;
+            }
+            p = p.subst;
+        }
+        return p;
+    }
+
+    public Value apply(Value i) {
+        if (i != null) {
+            return getSubst(i);
+        }
+        return i;
+    }
+}