introduce a singleton empty EconomicSet

Author: d-kozak

sdk/src/org.graalvm.collections.test/src/org/graalvm/collections/test/EmptyEconomicSetTest.java

@@ -0,0 +1,90 @@
+/*
+ * Copyright (c) 2025, Oracle and/or its affiliates. All rights reserved.
+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
+ *
+ * The Universal Permissive License (UPL), Version 1.0
+ *
+ * Subject to the condition set forth below, permission is hereby granted to any
+ * person obtaining a copy of this software, associated documentation and/or
+ * data (collectively the "Software"), free of charge and under any and all
+ * copyright rights in the Software, and any and all patent rights owned or
+ * freely licensable by each licensor hereunder covering either (i) the
+ * unmodified Software as contributed to or provided by such licensor, or (ii)
+ * the Larger Works (as defined below), to deal in both
+ *
+ * (a) the Software, and
+ *
+ * (b) any piece of software and/or hardware listed in the lrgrwrks.txt file if
+ * one is included with the Software each a "Larger Work" to which the Software
+ * is contributed by such licensors),
+ *
+ * without restriction, including without limitation the rights to copy, create
+ * derivative works of, display, perform, and distribute the Software and make,
+ * use, sell, offer for sale, import, export, have made, and have sold the
+ * Software and the Larger Work(s), and to sublicense the foregoing rights on
+ * either these or other terms.
+ *
+ * This license is subject to the following condition:
+ *
+ * The above copyright notice and either this complete permission notice or at a
+ * minimum a reference to the UPL must be included in all copies or substantial
+ * portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+package org.graalvm.collections.test;
+
+import java.util.NoSuchElementException;
+
+import org.graalvm.collections.EconomicSet;
+import org.junit.Assert;
+import org.junit.Test;
+
+public class EmptyEconomicSetTest {
+
+    @Test
+    public void testIsEmpty() {
+        Assert.assertTrue(EconomicSet.emptySet().isEmpty());
+    }
+
+    @Test
+    public void testSizeZero() {
+        Assert.assertEquals(0, EconomicSet.emptySet().size());
+    }
+
+    @Test(expected = IllegalArgumentException.class)
+    public void testAdd() {
+        EconomicSet.emptySet().add(1);
+    }
+
+    @Test(expected = IllegalArgumentException.class)
+    public void testRemove() {
+        EconomicSet.emptySet().remove(1);
+    }
+
+    @Test(expected = IllegalArgumentException.class)
+    public void testClear() {
+        EconomicSet.emptySet().clear();
+    }
+
+    @Test
+    public void testContains() {
+        Assert.assertFalse(EconomicSet.emptySet().contains(1));
+    }
+
+    @Test
+    public void testIteratorAlwaysEmpty() {
+        Assert.assertFalse(EconomicSet.emptySet().iterator().hasNext());
+    }
+
+    @Test(expected = NoSuchElementException.class)
+    public void testIteratorThrowsException() {
+        EconomicSet.emptySet().iterator().next();
+    }
+}

sdk/src/org.graalvm.collections/snapshot.sigtest

@@ -136,6 +136,7 @@ meth public static <%0 extends java.lang.Object> org.graalvm.collections.Economi
 meth public static <%0 extends java.lang.Object> org.graalvm.collections.EconomicSet<{%%0}> create(org.graalvm.collections.Equivalence,int)
 meth public static <%0 extends java.lang.Object> org.graalvm.collections.EconomicSet<{%%0}> create(org.graalvm.collections.Equivalence,org.graalvm.collections.UnmodifiableEconomicSet<{%%0}>)
 meth public static <%0 extends java.lang.Object> org.graalvm.collections.EconomicSet<{%%0}> create(org.graalvm.collections.UnmodifiableEconomicSet<{%%0}>)
+meth public static org.graalvm.collections.EconomicSet emptySet()
 meth public void addAll(java.lang.Iterable<{org.graalvm.collections.EconomicSet%0}>)
 meth public void addAll(java.util.Iterator<{org.graalvm.collections.EconomicSet%0}>)
 meth public void addAll(org.graalvm.collections.EconomicSet<{org.graalvm.collections.EconomicSet%0}>)

sdk/src/org.graalvm.collections/src/org/graalvm/collections/EconomicSet.java

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2017, 2019, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2017, 2025, Oracle and/or its affiliates. All rights reserved.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
  * The Universal Permissive License (UPL), Version 1.0
@@ -206,4 +206,14 @@ static <E> EconomicSet<E> create(Equivalence strategy, int initialCapacity) {
     static <E> EconomicSet<E> create(Equivalence strategy, UnmodifiableEconomicSet<E> c) {
         return EconomicMapImpl.create(strategy, c, true);
     }
+
+    /**
+     * Return an empty, unmodifiable {@link EconomicSet}.
+     *
+     * @since 25.0
+     */
+    @SuppressWarnings("unchecked")
+    static <E> EconomicSet<E> emptySet() {
+        return (EconomicSet<E>) EmptySet.EMPTY_SET;
+    }
 }

sdk/src/org.graalvm.collections/src/org/graalvm/collections/EmptySet.java

@@ -0,0 +1,85 @@
+/*
+ * Copyright (c) 2025, Oracle and/or its affiliates. All rights reserved.
+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
+ *
+ * The Universal Permissive License (UPL), Version 1.0
+ *
+ * Subject to the condition set forth below, permission is hereby granted to any
+ * person obtaining a copy of this software, associated documentation and/or
+ * data (collectively the "Software"), free of charge and under any and all
+ * copyright rights in the Software, and any and all patent rights owned or
+ * freely licensable by each licensor hereunder covering either (i) the
+ * unmodified Software as contributed to or provided by such licensor, or (ii)
+ * the Larger Works (as defined below), to deal in both
+ *
+ * (a) the Software, and
+ *
+ * (b) any piece of software and/or hardware listed in the lrgrwrks.txt file if
+ * one is included with the Software each a "Larger Work" to which the Software
+ * is contributed by such licensors),
+ *
+ * without restriction, including without limitation the rights to copy, create
+ * derivative works of, display, perform, and distribute the Software and make,
+ * use, sell, offer for sale, import, export, have made, and have sold the
+ * Software and the Larger Work(s), and to sublicense the foregoing rights on
+ * either these or other terms.
+ *
+ * This license is subject to the following condition:
+ *
+ * The above copyright notice and either this complete permission notice or at a
+ * minimum a reference to the UPL must be included in all copies or substantial
+ * portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+package org.graalvm.collections;
+
+import java.util.Iterator;
+
+/**
+ * Singleton instance for empty set. Reuses empty iterator from {@link EmptyMap}.
+ */
+class EmptySet {
+    static final EconomicSet<Object> EMPTY_SET = new EconomicSet<>() {
+        @Override
+        public boolean add(Object element) {
+            throw new IllegalArgumentException("Cannot modify the always-empty set");
+        }
+
+        @Override
+        public void remove(Object element) {
+            throw new IllegalArgumentException("Cannot modify the always-empty set");
+        }
+
+        @Override
+        public void clear() {
+            throw new IllegalArgumentException("Cannot modify the always-empty set");
+        }
+
+        @Override
+        public boolean contains(Object element) {
+            return false;
+        }
+
+        @Override
+        public int size() {
+            return 0;
+        }
+
+        @Override
+        public boolean isEmpty() {
+            return true;
+        }
+
+        @Override
+        public Iterator<Object> iterator() {
+            return EmptyMap.EMPTY_ITERATOR;
+        }
+    };
+}

substratevm/src/com.oracle.svm.hosted/src/com/oracle/svm/hosted/code/CompilationGraph.java

@@ -120,8 +120,8 @@ static CompilationGraph encode(StructuredGraph graph) {
         return new CompilationGraph(
                         GraphEncoder.encodeSingleGraph(graph, AnalysisParsedGraph.HOST_ARCHITECTURE),
                         graph.getNodeCount(),
-                        invokeInfos, // todo is there an empty global singleton we could use?
-                        allocationInfos);
+                        invokeInfos.isEmpty() ? EconomicSet.emptySet() : invokeInfos,
+                        allocationInfos.isEmpty() ? EconomicSet.emptySet() : allocationInfos);
     }
 
     public EncodedGraph getEncodedGraph() {