1 /*
 2  * Copyright (c) 2026, Oracle and/or its affiliates. All rights reserved.
 3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
 4  *
 5  * This code is free software; you can redistribute it and/or modify it
 6  * under the terms of the GNU General Public License version 2 only, as
 7  * published by the Free Software Foundation.  Oracle designates this
 8  * particular file as subject to the "Classpath" exception as provided
 9  * by Oracle in the LICENSE file that accompanied this code.
10  *
11  * This code is distributed in the hope that it will be useful, but WITHOUT
12  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
13  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
14  * version 2 for more details (a copy is included in the LICENSE file that
15  * accompanied this code).
16  *
17  * You should have received a copy of the GNU General Public License version
18  * 2 along with this work; if not, write to the Free Software Foundation,
19  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
20  *
21  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
22  * or visit www.oracle.com if you need additional information or have any
23  * questions.
24  */
25 
26 package jdk.incubator.code.internal;
27 
28 import jdk.incubator.code.Block;
29 import jdk.incubator.code.CodeContext;
30 import jdk.incubator.code.CodeTransformer;
31 import jdk.incubator.code.Op;
32 import jdk.incubator.code.dialect.core.CoreOp;
33 import jdk.incubator.code.dialect.java.JavaOp;
34 
35 /**
36  * A transformer that removes unused {@link jdk.incubator.code.dialect.core.CoreOp.ConstantOp}.
37  */
38 public class RemoveUnusedConstantTransformer implements CodeTransformer {
39     private RemoveUnusedConstantTransformer() {}
40 
41     private static final RemoveUnusedConstantTransformer INSTANCE = new RemoveUnusedConstantTransformer();
42 
43     /**
44      * Transforms an operation, by removing unused constants.
45      *
46      * @param op  the operation to transform
47      * @param <O> the type of operation
48      * @return the transformed operation
49      */
50     @SuppressWarnings("unchecked")
51     public static <O extends Op> O transform(Op op) {
52         return (O) op.transform(CodeContext.create(), INSTANCE);
53     }
54 
55     @Override
56     public Block.Builder acceptOp(Block.Builder builder, Op op) {
57         if (op instanceof CoreOp.ConstantOp
58                 && op.result() != null
59                 && op.result().uses().isEmpty()
60                 // label constant cannot be removed
61                 && !(op.ancestorOp() instanceof JavaOp.LabeledOp labeled && labeled.label() == op)) {
62             return builder;
63         }
64         builder.add(op);
65         return builder;
66     }
67 }