8352893: C2: OrL/INode::add_ring optimize (x | -1) to -1

Reviewed-by: epeter, thartmann, kvn

src/hotspot/share/opto/addnode.cpp

@@ -854,6 +854,12 @@ const Type *OrINode::add_ring( const Type *t0, const Type *t1 ) const {
     }
   }
 
+  // If either input is all ones, the output is all ones.
+  // x | ~0 == ~0 <==> x | -1 == -1
+  if (r0 == TypeInt::MINUS_1 || r1 == TypeInt::MINUS_1) {
+    return TypeInt::MINUS_1;
+  }
+
   // If either input is not a constant, just return all integers.
   if( !r0->is_con() || !r1->is_con() )
     return TypeInt::INT;        // Any integer, but still no symbols.
@@ -911,6 +917,12 @@ const Type *OrLNode::add_ring( const Type *t0, const Type *t1 ) const {
   const TypeLong *r0 = t0->is_long(); // Handy access
   const TypeLong *r1 = t1->is_long();
 
+  // If either input is all ones, the output is all ones.
+  // x | ~0 == ~0 <==> x | -1 == -1
+  if (r0 == TypeLong::MINUS_1 || r1 == TypeLong::MINUS_1) {
+    return TypeLong::MINUS_1;
+  }
+
   // If either input is not a constant, just return all integers.
   if( !r0->is_con() || !r1->is_con() )
     return TypeLong::LONG;      // Any integer, but still no symbols.

test/hotspot/jtreg/compiler/integerArithmetic/TestOrSaturate.java

@@ -0,0 +1,87 @@
+/*
+ * Copyright (c) 2025, 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.
+ *
+ * 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 compiler.integerArithmetic;
+
+import compiler.lib.ir_framework.*;
+import java.util.Random;
+import jdk.test.lib.Utils;
+import jdk.test.lib.Asserts;
+
+/*
+ * @test
+ * @bug 8352893
+ * @summary Test that an or with all bits set is folded to all bits (x | -1 == -1).
+ * @key randomness
+ * @library / /test/lib
+ * @run driver compiler.integerArithmetic.TestOrSaturate
+ */
+
+public class TestOrSaturate {
+    public static void main(String[] args) {
+        TestFramework.run();
+    }
+
+    private static final Random random = Utils.getRandomInstance();
+
+    @Run(test = {"testL", "testI", "testDelayed"})
+    public static void check() {
+        Asserts.assertEQ(-1L, testL(random.nextLong()));
+        Asserts.assertEQ(-1, testI(random.nextInt()));
+        Asserts.assertEQ(-1, testDelayed(random.nextInt()));
+    }
+
+    @Test
+    @IR(failOn = { IRNode.OR_L })
+    // Tests that the OrLNode is folded if one operand is -1.
+    private static long testL(long x) {
+        return x | -1L;
+    }
+
+    @Test
+    @IR(failOn = { IRNode.OR_I })
+    // Tests that the OrINode is folded if one operand is -1.
+    private static int testI(int x) {
+        return x | -1;
+    }
+
+    @Test
+    @IR(counts = {IRNode.OR_I, "1"},
+        phase = CompilePhase.AFTER_PARSING)
+    @IR(failOn = { IRNode.OR_I })
+    // Tests that the OrI node is folded after parsing if one operand is -1.
+    private static int testDelayed(int x) {
+        int min1 = 42;
+        int limit = 2;
+
+        // Ensure that min1 == -1 is only known after some constant propagation.
+        for (; limit < 4; limit *= 2) {}
+        for (int i = 2; i < limit; i++) {
+            min1 = -1;
+        }
+
+        // Will only be folded after min1 == -1 is established.
+        return x | min1;
+    }
+}

test/hotspot/jtreg/compiler/lib/ir_framework/IRNode.java

@@ -1440,6 +1440,16 @@ public class IRNode {
         optoOnly(OOPMAP_WITH, regex);
     }
 
+    public static final String OR_I = PREFIX + "OR_I" + POSTFIX;
+    static {
+        beforeMatchingNameRegex(OR_I, "OrI");
+    }
+
+    public static final String OR_L = PREFIX + "OR_L" + POSTFIX;
+    static {
+        beforeMatchingNameRegex(OR_L, "OrL");
+    }
+
     public static final String OR_VB = VECTOR_PREFIX + "OR_VB" + POSTFIX;
     static {
         vectorNode(OR_VB, "OrV", TYPE_BYTE);