Improve AbsNode canonicalization

Add an extra canonicalization to AbsNode with NegateNode inputs,
and also add unit tests.

Also fix an incorrect return value in its create factory method.

Author: kethomassen

compiler/src/org.graalvm.compiler.core.test/src/org/graalvm/compiler/core/test/AbsCanonicalizationTest.java

@@ -0,0 +1,75 @@
+/*
+ * Copyright (c) 2021, 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.  Oracle designates this
+ * particular file as subject to the "Classpath" exception as provided
+ * by Oracle in the LICENSE file that accompanied this code.
+ *
+ * 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 org.graalvm.compiler.core.test;
+
+import org.graalvm.compiler.nodes.StructuredGraph;
+import org.graalvm.compiler.nodes.calc.AbsNode;
+import org.graalvm.compiler.nodes.calc.NegateNode;
+import org.junit.Assert;
+import org.junit.Test;
+
+public class AbsCanonicalizationTest extends GraalCompilerTest {
+    public static double absReference(double x) {
+        return Math.abs(x);
+    }
+
+    public static double absAbs(double x) {
+        return Math.abs(Math.abs(x));
+    }
+
+    public static double absNegate(double x) {
+        return Math.abs(-x);
+    }
+
+    @Test
+    public void testAbsNegate() {
+        StructuredGraph graph = parseEager("absNegate", StructuredGraph.AllowAssumptions.YES);
+        createInliningPhase().apply(graph, getDefaultHighTierContext());
+        createCanonicalizerPhase().apply(graph, getProviders());
+
+        StructuredGraph referenceGraph = parseEager("absReference", StructuredGraph.AllowAssumptions.YES);
+        assertEquals(referenceGraph, graph);
+        Assert.assertEquals(0, graph.getNodes().filter(NegateNode.class).count());
+
+        testAgainstExpected(graph.method(), new Result(absNegate(-Double.MAX_VALUE), null), (Object) null, Double.MAX_VALUE);
+        testAgainstExpected(graph.method(), new Result(absNegate(0d), null), (Object) null, 0d);
+        testAgainstExpected(graph.method(), new Result(absNegate(Double.MAX_VALUE), null), (Object) null, Double.MAX_VALUE);
+    }
+
+    @Test
+    public void testAbsAbs() {
+        StructuredGraph graph = parseEager("absAbs", StructuredGraph.AllowAssumptions.YES);
+        createInliningPhase().apply(graph, getDefaultHighTierContext());
+        createCanonicalizerPhase().apply(graph, getProviders());
+
+        StructuredGraph referenceGraph = parseEager("absReference", StructuredGraph.AllowAssumptions.YES);
+        assertEquals(referenceGraph, graph);
+        Assert.assertEquals(1, graph.getNodes().filter(AbsNode.class).count());
+
+        testAgainstExpected(graph.method(), new Result(absAbs(-Double.MAX_VALUE), null), (Object) null, Double.MAX_VALUE);
+        testAgainstExpected(graph.method(), new Result(absAbs(0d), null), (Object) null, 0d);
+        testAgainstExpected(graph.method(), new Result(absAbs(Double.MAX_VALUE), null), (Object) null, Double.MAX_VALUE);
+    }
+}

compiler/src/org.graalvm.compiler.nodes/src/org/graalvm/compiler/nodes/calc/AbsNode.java

@@ -56,7 +56,7 @@ public static ValueNode create(ValueNode value, NodeView view) {
         if (synonym != null) {
             return synonym;
         }
-        return new NegateNode(value);
+        return new AbsNode(value);
     }
 
     protected static ValueNode findSynonym(ValueNode forValue, NodeView view) {
@@ -65,6 +65,14 @@ protected static ValueNode findSynonym(ValueNode forValue, NodeView view) {
         if (synonym != null) {
             return synonym;
         }
+        if (forValue instanceof AbsNode) {
+            return forValue;
+        }
+        // abs(-x) => abs(x)
+        if (forValue instanceof NegateNode) {
+            NegateNode negate = (NegateNode) forValue;
+            return AbsNode.create(negate.getValue(), view);
+        }
         return null;
     }
 
@@ -79,8 +87,9 @@ public ValueNode canonical(CanonicalizerTool tool, ValueNode forValue) {
         if (ret != this) {
             return ret;
         }
-        if (forValue instanceof AbsNode) {
-            return forValue;
+        ValueNode synonym = findSynonym(forValue, NodeView.from(tool));
+        if (synonym != null) {
+            return synonym;
         }
         return this;
     }