# HG changeset patch
# User Lukas Stadler <lukas.stadler@oracle.com>
# Date 1406118257 -7200
# Node ID 4209ec855c1ccb1b6af6c3c76891a58b28b0842c
# Parent  173da8c3095dcecf55500efe948ccb89f412722a
cleanups and doc for PhiNode.singleValue

diff -r 173da8c3095d -r 4209ec855c1c graal/com.oracle.graal.loop/src/com/oracle/graal/loop/InductionVariables.java
--- a/graal/com.oracle.graal.loop/src/com/oracle/graal/loop/InductionVariables.java	Wed Jul 23 14:20:27 2014 +0200
+++ b/graal/com.oracle.graal.loop/src/com/oracle/graal/loop/InductionVariables.java	Wed Jul 23 14:24:17 2014 +0200
@@ -51,7 +51,7 @@
         AbstractEndNode forwardEnd = loopBegin.forwardEnd();
         for (PhiNode phi : loopBegin.phis()) {
             ValueNode backValue = phi.singleBackValue();
-            if (backValue == PhiNode.NO_VALUE) {
+            if (backValue == PhiNode.MULTIPLE_VALUES) {
                 continue;
             }
             ValueNode stride = addSub(backValue, phi);
diff -r 173da8c3095d -r 4209ec855c1c graal/com.oracle.graal.nodes/src/com/oracle/graal/nodes/PhiNode.java
--- a/graal/com.oracle.graal.nodes/src/com/oracle/graal/nodes/PhiNode.java	Wed Jul 23 14:20:27 2014 +0200
+++ b/graal/com.oracle.graal.nodes/src/com/oracle/graal/nodes/PhiNode.java	Wed Jul 23 14:24:17 2014 +0200
@@ -137,10 +137,15 @@
         values().remove(index);
     }
 
-    public static final ValueNode NO_VALUE = new ValueNode(null) {
+    public static final ValueNode MULTIPLE_VALUES = new ValueNode(null) {
         // empty dummy class
     };
 
+    /**
+     * If all inputs are the same value, this value is returned, otherwise {@link #MULTIPLE_VALUES}.
+     * Note that {@code null} is a valid return value, since {@link GuardPhiNode}s can have
+     * {@code null} inputs.
+     */
     public ValueNode singleValue() {
         Iterator<ValueNode> iterator = values().iterator();
         ValueNode singleValue = iterator.next();
@@ -148,13 +153,18 @@
             ValueNode value = iterator.next();
             if (value != this) {
                 if (value != singleValue) {
-                    return NO_VALUE;
+                    return MULTIPLE_VALUES;
                 }
             }
         }
         return singleValue;
     }
 
+    /**
+     * If all inputs (but the first one) are the same value, this value is returned, otherwise
+     * {@link #MULTIPLE_VALUES}. Note that {@code null} is a valid return value, since
+     * {@link GuardPhiNode}s can have {@code null} inputs.
+     */
     public ValueNode singleBackValue() {
         assert merge() instanceof LoopBeginNode;
         Iterator<ValueNode> iterator = values().iterator();
@@ -162,7 +172,7 @@
         ValueNode singleValue = iterator.next();
         while (iterator.hasNext()) {
             if (iterator.next() != singleValue) {
-                return NO_VALUE;
+                return MULTIPLE_VALUES;
             }
         }
         return singleValue;
@@ -172,7 +182,7 @@
     public void simplify(SimplifierTool tool) {
         ValueNode singleValue = singleValue();
 
-        if (singleValue != NO_VALUE) {
+        if (singleValue != MULTIPLE_VALUES) {
             for (Node node : usages().snapshot()) {
                 if (node instanceof ProxyNode && ((ProxyNode) node).proxyPoint() instanceof LoopExitNode && ((LoopExitNode) ((ProxyNode) node).proxyPoint()).loopBegin() == merge) {
                     tool.addToWorkList(node.usages());
diff -r 173da8c3095d -r 4209ec855c1c graal/com.oracle.graal.nodes/src/com/oracle/graal/nodes/util/GraphUtil.java
--- a/graal/com.oracle.graal.nodes/src/com/oracle/graal/nodes/util/GraphUtil.java	Wed Jul 23 14:20:27 2014 +0200
+++ b/graal/com.oracle.graal.nodes/src/com/oracle/graal/nodes/util/GraphUtil.java	Wed Jul 23 14:24:17 2014 +0200
@@ -174,7 +174,7 @@
         }
 
         ValueNode singleValue = phiNode.singleValue();
-        if (singleValue != PhiNode.NO_VALUE) {
+        if (singleValue != PhiNode.MULTIPLE_VALUES) {
             Collection<PhiNode> phiUsages = phiNode.usages().filter(PhiNode.class).snapshot();
             Collection<ProxyNode> proxyUsages = phiNode.usages().filter(ProxyNode.class).snapshot();
             phiNode.graph().replaceFloating(phiNode, singleValue);
@@ -343,7 +343,7 @@
                 v = ((ValueProxy) v).getOriginalNode();
             } else if (v instanceof PhiNode) {
                 v = ((PhiNode) v).singleValue();
-                if (v == PhiNode.NO_VALUE) {
+                if (v == PhiNode.MULTIPLE_VALUES) {
                     v = null;
                 }
             } else {