src/jdk.internal.vm.ci/share/classes/jdk/vm/ci/code/RegisterConfig.java

/*
 * Copyright (c) 2009, 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 jdk.vm.ci.code;

import java.util.List;
import jdk.vm.ci.code.CallingConvention.Type;
import jdk.vm.ci.meta.JavaKind;
import jdk.vm.ci.meta.JavaType;
import jdk.vm.ci.meta.PlatformKind;
import jdk.vm.ci.meta.ValueKind;

/**
 * A register configuration binds roles and {@linkplain RegisterAttributes attributes} to physical
 * registers.
 */
public interface RegisterConfig {

    /**
     * Gets the register to be used for returning a value of a given kind.
     */
    Register getReturnRegister(JavaKind kind);

    /**
     * Gets the maximum allowed size of the frame.
     */
    default int getMaximumFrameSize() {
        return Integer.MAX_VALUE;
    }

    /**
     * Gets the register used as the frame pointer. Spill slots and outgoing stack-based arguments
     * are addressed relative to this register.
     */
    Register getFrameRegister();

    /**
     * Gets the calling convention describing how arguments are passed.
     *
     * @param type the type of calling convention being requested
     * @param returnType the return type (can be null for methods returning {@code void})
     * @param parameterTypes the types of the arguments of the call
     * @param valueKindFactory the factory to create custom {@link ValueKind ValueKinds}
     */
    CallingConvention getCallingConvention(Type type, JavaType returnType, JavaType[] parameterTypes, ValueKindFactory<?> valueKindFactory);

    /**
     * Gets the ordered set of registers that are can be used to pass parameters according to a
     * given calling convention.
     *
     * @param type the type of calling convention
     * @param kind specifies what kind of registers is being requested
     * @return the ordered set of registers that may be used to pass parameters in a call conforming
     *         to {@code type}
     */
    List<Register> getCallingConventionRegisters(Type type, JavaKind kind);

    /**
     * Gets the set of all registers that might be used by the register allocator.
     */
    List<Register> getAllocatableRegisters();

    /**
     * Filters a set of registers and returns only those that can be used by the register allocator
     * for a value of a particular kind.
     */
    List<Register> filterAllocatableRegisters(PlatformKind kind, List<Register> registers);

    /**
     * Gets the registers whose values must be preserved by a method across any call it makes.
     */
    List<Register> getCallerSaveRegisters();

    /**
     * Gets the registers whose values must be preserved by the callee.
     */
    List<Register> getCalleeSaveRegisters();

    /**
     * Returns the storage kind for a callee-save register, which determines how the register is
     * saved and restored. For example, according to the Windows x64 ABI, the upper portions of
     * XMM0-XMM15 are considered destroyed, so saving the full width of these registers is not
     * necessary.
     */
    default PlatformKind getCalleeSaveRegisterStorageKind(Architecture arch, Register calleeSaveRegister) {
        return arch.getLargestStorableKind(calleeSaveRegister.getRegisterCategory());
    }

    /**
     * Gets a map from register {@linkplain Register#number numbers} to register
     * {@linkplain RegisterAttributes attributes} for this register configuration.
     *
     * @return a list where an element at index i holds the attributes of the register whose
     *         number is i
     */
    List<RegisterAttributes> getAttributesMap();

    /**
     * Determines if all {@link #getAllocatableRegisters() allocatable} registers are
     * {@link #getCallerSaveRegisters() caller saved}.
     */
    boolean areAllAllocatableRegistersCallerSaved();
}