--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/graal/com.oracle.truffle.dsl.processor/src/com/oracle/truffle/dsl/processor/model/GuardExpression.java	Mon Aug 11 15:57:14 2014 +0200
@@ -0,0 +1,87 @@
+package com.oracle.truffle.dsl.processor.model;
+
+import java.util.*;
+
+public final class GuardExpression {
+
+    private GuardData resolvedGuard;
+
+    private final String guardName;
+    private final boolean negated;
+
+    public GuardExpression(String expression) {
+        if (expression.startsWith("!")) {
+            guardName = expression.substring(1, expression.length());
+            negated = true;
+        } else {
+            guardName = expression;
+            negated = false;
+        }
+    }
+
+    public boolean isResolved() {
+        return resolvedGuard != null;
+    }
+
+    public String getGuardName() {
+        return guardName;
+    }
+
+    public void setGuard(GuardData guard) {
+        this.resolvedGuard = guard;
+    }
+
+    @Override
+    public boolean equals(Object obj) {
+        if (obj instanceof GuardExpression) {
+            GuardExpression other = (GuardExpression) obj;
+            if (isResolved() && other.isResolved()) {
+                return resolvedGuard.equals(other.resolvedGuard) && negated == other.negated;
+            } else {
+                return guardName.equals(other.guardName) && negated == other.negated;
+            }
+        }
+        return false;
+    }
+
+    @Override
+    public int hashCode() {
+        return Objects.hash(guardName, negated, resolvedGuard);
+    }
+
+    public final boolean implies(GuardExpression other) {
+        if (other == this) {
+            return true;
+        }
+        if (getGuardName().equals(other.getGuardName())) {
+            if (isNegated() == other.isNegated()) {
+                return true;
+            }
+        }
+
+        if (isResolved() && other.isResolved()) {
+            for (GuardExpression implies : getResolvedGuard().getImpliesExpressions()) {
+                if (implies.getGuardName().equals(other.getGuardName())) {
+                    if (implies.isNegated() == other.isNegated()) {
+                        return true;
+                    }
+                }
+            }
+        }
+        return false;
+    }
+
+    @Override
+    public String toString() {
+        return (negated ? "!" : "") + guardName;
+    }
+
+    public boolean isNegated() {
+        return negated;
+    }
+
+    public GuardData getResolvedGuard() {
+        return resolvedGuard;
+    }
+
+}