[GR-65433] Correction of BitSets.equals().

PullRequest: graal/20952

Author: iamstolis

regex/src/com.oracle.truffle.regex.test/src/com/oracle/truffle/regex/tregex/TBitSetTest.java

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2018, 2021, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2018, 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
@@ -250,6 +250,23 @@ public void testSubtract() {
         reset();
     }
 
+    @Test
+    public void testEquals() {
+        TBitSet small = new TBitSet(128);
+        TBitSet large = new TBitSet(256);
+        Assert.assertTrue(small.equals(large));
+        Assert.assertTrue(large.equals(small));
+        small.set(42);
+        Assert.assertFalse(small.equals(large));
+        Assert.assertFalse(large.equals(small));
+        large.set(42);
+        Assert.assertTrue(small.equals(large));
+        Assert.assertTrue(large.equals(small));
+        large.set(211);
+        Assert.assertFalse(small.equals(large));
+        Assert.assertFalse(large.equals(small));
+    }
+
     private void checkSet(int i) {
         oracle.set(i);
         bitSet.set(i);

regex/src/com.oracle.truffle.regex/src/com/oracle/truffle/regex/util/BitSets.java

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2020, 2024, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2020, 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
@@ -260,12 +260,12 @@ public static boolean equals(long[] bs1, long[] bs2) {
             }
         }
         for (int i = bs1.length; i < bs2.length; i++) {
-            if (bs1[i] != 0) {
+            if (bs2[i] != 0) {
                 return false;
             }
         }
         for (int i = bs2.length; i < bs1.length; i++) {
-            if (bs2[i] != 0) {
+            if (bs1[i] != 0) {
                 return false;
             }
         }