/*
 * Copyright (c) 2009, 2010, 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 com.oracle.max.graal.compiler.lir;

import com.sun.cri.ci.*;

/**
 * An instruction operand. If the register allocator can modify this operand (e.g. to replace a
 * variable with a register), then it will have a corresponding entry in the {@link LIRInstruction#allocatorOperands}
 * list of an instruction.
 *
 * @author Doug Simon
 */
public class LIROperand {

    /**
     * The value of the operand.
     */
    CiValue value;

    LIROperand(CiValue value) {
        this.value = value;
    }

    /**
     * Gets the value of this operand. This may still be a {@linkplain CiVariable}
     * if the register allocator has not yet assigned a register or stack address to the operand.
     *
     * @param inst the instruction containing this operand
     */
    public CiValue value(LIRInstruction inst) {
        return value;
    }

    @Override
    public String toString() {
        return value.toString();
    }

    static class LIRVariableOperand extends LIROperand {
        /**
         * Index into an instruction's {@linkplain LIRInstruction#allocatorOperands allocator operands}.
         */
        final int index;

        LIRVariableOperand(int index) {
            super(null);
            this.index = index;
        }

        @Override
        public CiValue value(LIRInstruction inst) {
            if (value == null) {
                CiValue value = inst.allocatorOperands.get(index);
                if (value.isVariable()) {
                    return value;
                }
                this.value = value;
            }
            return value;
        }

        @Override
        public String toString() {
            if (value == null) {
                return "operands[" + index + "]";
            }
            return value.toString();
        }
    }

    /**
     * An address operand with at least one {@linkplain CiVariable variable} constituent.
     */
    static class LIRAddressOperand extends LIROperand {
        int base;
        int index;

        LIRAddressOperand(int base, int index, CiAddress address) {
            super(address);
            assert base != -1 || index != -1 : "address should have at least one variable part";
            this.base = base;
            this.index = index;
        }

        @Override
        public CiValue value(LIRInstruction inst) {
            if (base != -1 || index != -1) {
                CiAddress address = (CiAddress) value;
                CiValue baseOperand = base == -1 ? address.base : inst.allocatorOperands.get(base);
                CiValue indexOperand = index == -1 ? address.index : inst.allocatorOperands.get(index);
                if (address.index.isLegal()) {
                    assert indexOperand.isVariableOrRegister();
                    if (baseOperand.isVariable() || indexOperand.isVariable()) {
                        return address;
                    }
                } else {
                    if (baseOperand.isVariable()) {
                        return address;
                    }
                }
                value = new CiAddress(address.kind, baseOperand, indexOperand, address.scale, address.displacement);
                base = -1;
                index = -1;
            }
            return value;
        }

        @Override
        public String toString() {
            return value.toString();
        }
    }
}