# HG changeset patch
# User Lukas Stadler <lukas.stadler@jku.at>
# Date 1371219882 -7200
# Node ID 09baba95f1aee0f59dc7395d866c1a5854013e66
# Parent  a4e7a7dc74f3b20fe5ce2a382b7fb1d06f157897
detect distinct values by looking at integer masks

diff -r a4e7a7dc74f3 -r 09baba95f1ae graal/com.oracle.graal.compiler.test/src/com/oracle/graal/compiler/test/StampCanonicalizerTest.java
--- a/graal/com.oracle.graal.compiler.test/src/com/oracle/graal/compiler/test/StampCanonicalizerTest.java	Fri Jun 14 16:23:53 2013 +0200
+++ b/graal/com.oracle.graal.compiler.test/src/com/oracle/graal/compiler/test/StampCanonicalizerTest.java	Fri Jun 14 16:24:42 2013 +0200
@@ -96,6 +96,17 @@
         testZeroReturn("divStamp2");
     }
 
+    public static int distinctMask(int a, int b) {
+        int x = a & 0xaaaa;
+        int y = (b & 0x5555) | 0x1;
+        return x == y ? 1 : 0;
+    }
+
+    @Test
+    public void testDistinctMask() {
+        testZeroReturn("distinctMask");
+    }
+
     private void testZeroReturn(String methodName) {
         StructuredGraph graph = parse(methodName);
         new CanonicalizerPhase.Instance(runtime(), new Assumptions(false), true).apply(graph);
diff -r a4e7a7dc74f3 -r 09baba95f1ae graal/com.oracle.graal.nodes/src/com/oracle/graal/nodes/type/IntegerStamp.java
--- a/graal/com.oracle.graal.nodes/src/com/oracle/graal/nodes/type/IntegerStamp.java	Fri Jun 14 16:23:53 2013 +0200
+++ b/graal/com.oracle.graal.nodes/src/com/oracle/graal/nodes/type/IntegerStamp.java	Fri Jun 14 16:24:42 2013 +0200
@@ -129,7 +129,15 @@
     @Override
     public boolean alwaysDistinct(Stamp otherStamp) {
         IntegerStamp other = (IntegerStamp) otherStamp;
-        return lowerBound > other.upperBound || upperBound < other.lowerBound;
+        if (lowerBound > other.upperBound || upperBound < other.lowerBound) {
+            return true;
+        } else {
+            if ((mask & other.mask) == 0) {
+                // zero is the only common value if the masks don't overlap => check for non-zero
+                return lowerBound > 0 || upperBound < 0 || other.lowerBound > 0 || other.upperBound < 0;
+            }
+            return false;
+        }
     }
 
     @Override