src/java.base/share/classes/java/lang/classfile/instruction/ConstantInstruction.java

/*
 * Copyright (c) 2022, 2024, 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 java.lang.classfile.instruction;

import java.lang.classfile.CodeBuilder;
import java.lang.classfile.CodeElement;
import java.lang.classfile.CodeModel;
import java.lang.classfile.Instruction;
import java.lang.classfile.Opcode;
import java.lang.classfile.TypeKind;
import java.lang.classfile.constantpool.LoadableConstantEntry;
import java.lang.constant.ConstantDesc;

import jdk.internal.classfile.impl.AbstractInstruction;
import jdk.internal.classfile.impl.BytecodeHelpers;
import jdk.internal.classfile.impl.Util;

/**
 * Models a constant-load instruction in the {@code code} array of a {@code
 * Code} attribute, including {@linkplain IntrinsicConstantInstruction
 * "intrinsic"}, {@linkplain ArgumentConstantInstruction "argument"}, and
 * {@linkplain LoadConstantInstruction "load"} constant instructions.
 * Corresponding opcodes have a {@linkplain Opcode#kind() kind} of {@link
 * Opcode.Kind#CONSTANT}.  Delivered as a {@link CodeElement} when traversing
 * the elements of a {@link CodeModel}.
 * <p>
 * The loaded constant value is symbolically represented as a {@link ConstantDesc}:
 * {@snippet lang=text :
 * // @link substring="ConstantInstruction" target="CodeBuilder#loadConstant(ConstantDesc)" :
 * ConstantInstruction(ConstantDesc constantValue) // @link substring="constantValue" target="#constantValue()"
 * }
 *
 * @see Opcode.Kind#CONSTANT
 * @see CodeBuilder#loadConstant(ConstantDesc) CodeBuilder::loadConstant
 * @sealedGraph
 * @since 24
 */
public sealed interface ConstantInstruction extends Instruction {

    /**
     * {@return the constant value}
     */
    ConstantDesc constantValue();

    /**
     * {@return the {@linkplain TypeKind##computational-type computational type} of the constant}
     * This is derived from the {@link #constantValue() constantValue}.
     */
    TypeKind typeKind();

    /**
     * Models an "intrinsic constant" instruction, which encodes
     * the constant value in its opcode. Examples include {@link
     * Opcode#ACONST_NULL aconst_null} and {@link
     * Opcode#ICONST_0 iconst_0}.
     * <p>
     * An intrinsic constant instruction is composite:
     * {@snippet lang=text :
     * // @link substring="IntrinsicConstantInstruction" target="#ofIntrinsic" :
     * IntrinsicConstantInstruction(Opcode opcode) // @link substring="opcode" target="#opcode()"
     * }
     * where:
     * <dl>
     * <dt>{@link #opcode() opcode}</dt>
     * <dd>Must be of the constant kind and have a {@linkplain
     * Opcode#sizeIfFixed() fixed size} of 1.</dd>
     * </dl>
     *
     * @see Opcode.Kind#CONSTANT
     * @see ConstantInstruction#ofIntrinsic ConstantInstruction::ofIntrinsic
     * @since 24
     */
    sealed interface IntrinsicConstantInstruction extends ConstantInstruction
            permits AbstractInstruction.UnboundIntrinsicConstantInstruction {

        @Override
        default TypeKind typeKind() {
            return BytecodeHelpers.intrinsicConstantType(opcode());
        }
    }

    /**
     * Models an "argument constant" instruction, which encodes the
     * constant value in the instruction directly. Includes {@link
     * Opcode#BIPUSH bipush} and {@link Opcode#SIPUSH sipush} instructions.
     * <p>
     * An argument constant instruction is composite:
     * {@snippet lang=text :
     * // @link substring="ArgumentConstantInstruction" target="#ofArgument" :
     * ArgumentConstantInstruction(
     *     Opcode opcode, // @link substring="opcode" target="#opcode()"
     *     int constantValue // @link substring="constantValue" target="#constantValue()"
     * )
     * }
     * where:
     * <ul>
     * <li>{@code opcode} must be one of {@code bipush} or {@code sipush}.
     * <li>{@code constantValue} must be in the range of {@code byte}, {@code
     * [-128, 127]}, for {@code bipush},  and in the range of {@code short},
     * {@code [-32768, 32767]}, for {@code sipush}.
     * </ul>
     *
     * @see Opcode.Kind#CONSTANT
     * @see ConstantInstruction#ofArgument ConstantInstruction::ofArgument
     * @see CodeBuilder#loadConstant(int) CodeBuilder::loadConstant(int)
     * @see CodeBuilder#bipush CodeBuilder::bipush
     * @see CodeBuilder#sipush CodeBuilder::sipush
     * @since 24
     */
    sealed interface ArgumentConstantInstruction extends ConstantInstruction
            permits AbstractInstruction.BoundArgumentConstantInstruction,
                    AbstractInstruction.UnboundArgumentConstantInstruction {

        @Override
        Integer constantValue();

        @Override
        default TypeKind typeKind() {
            return TypeKind.INT;
        }
    }

    /**
     * Models a "load constant" instruction, which encodes the constant value
     * in the constant pool.  Includes {@link Opcode#LDC ldc} and {@link
     * Opcode#LDC_W ldc_w}, and {@link Opcode#LDC2_W ldc2_w} instructions.
     * <p>
     * A load constant instruction is composite:
     * {@snippet lang=text :
     * // @link substring="LoadConstantInstruction" target="CodeBuilder#ldc(LoadableConstantEntry)" :
     * LoadConstantInstruction(LoadableConstantEntry constantEntry) // @link substring="constantEntry" target="#constantEntry()"
     * }
     * <p>
     * A "load constant" instruction can load any constant value supported by
     * other constant-load instructions.  However, other instructions are
     * usually more optimized, avoiding extra constant pool entries and being
     * smaller.
     *
     * @see Opcode.Kind#CONSTANT
     * @see ConstantInstruction#ofLoad ConstantInstruction::ofLoad
     * @see CodeBuilder#ldc CodeBuilder::ldc
     * @since 24
     */
    sealed interface LoadConstantInstruction extends ConstantInstruction
            permits AbstractInstruction.BoundLoadConstantInstruction,
                    AbstractInstruction.UnboundLoadConstantInstruction {

        /**
         * {@return the constant value}
         */
        LoadableConstantEntry constantEntry();

        @Override
        default TypeKind typeKind() {
            return constantEntry().typeKind();
        }
    }

    /**
     * {@return an intrinsic constant instruction}
     *
     * @param op the opcode for the specific type of intrinsic constant instruction,
     *           which must be of kind {@link Opcode.Kind#CONSTANT}
     * @throws IllegalArgumentException if the opcode does not represent a constant
     *                                  with implicit value
     */
    static IntrinsicConstantInstruction ofIntrinsic(Opcode op) {
        Util.checkKind(op, Opcode.Kind.CONSTANT);
        if (op.sizeIfFixed() != 1)
            throw new IllegalArgumentException(String.format("Wrong opcode specified; found %s, expected xCONST_val", op));
        return new AbstractInstruction.UnboundIntrinsicConstantInstruction(op);
    }

    /**
     * {@return an argument constant instruction}
     * <p>
     * {@code value} must be in the range of {@code byte}, {@code [-128, 127]},
     * for {@link Opcode#BIPUSH}, and in the range of {@code short}, {@code
     * [-32768, 32767]}, for {@link Opcode#SIPUSH}.
     *
     * @param op the opcode for the specific type of argument constant instruction,
     *           which must be {@link Opcode#BIPUSH} or {@link Opcode#SIPUSH}
     * @param value the constant value
     * @throws IllegalArgumentException if the opcode is not {@link Opcode#BIPUSH}
     *         or {@link Opcode#SIPUSH}, or if the constant value is out of range
     *         for the opcode
     */
    static ArgumentConstantInstruction ofArgument(Opcode op, int value) {
        if (op == Opcode.BIPUSH) {
            BytecodeHelpers.validateBipush(value);
        } else if (op == Opcode.SIPUSH) {
            BytecodeHelpers.validateSipush(value);
        } else {
            throw new IllegalArgumentException(String.format("Wrong opcode specified; found %s, expected BIPUSH or SIPUSH", op));
        }
        return new AbstractInstruction.UnboundArgumentConstantInstruction(op, value);
    }

    /**
     * {@return a load constant instruction}
     *
     * @param op the opcode for the specific type of load constant instruction,
     *           which must be of kind {@link Opcode.Kind#CONSTANT}
     * @param constant the constant value
     * @throws IllegalArgumentException if the opcode is not {@link Opcode#LDC},
     *                                  {@link Opcode#LDC_W}, or {@link Opcode#LDC2_W}
     */
    static LoadConstantInstruction ofLoad(Opcode op, LoadableConstantEntry constant) {
        Util.checkKind(op, Opcode.Kind.CONSTANT);
        if (op != Opcode.LDC && op != Opcode.LDC_W && op != Opcode.LDC2_W)
            throw new IllegalArgumentException(String.format("Wrong opcode specified; found %s, expected LDC, LDC_W or LDC2_W", op));
        return new AbstractInstruction.UnboundLoadConstantInstruction(op, constant);
    }
}