com.oracle.truffle.sl.nodes.local.SLReadLocalVariableNode Maven / Gradle / Ivy

Go to download
Show more of this group Show more artifacts with this name
Show all versions of truffle-sl Show documentation
Truffle SL is an example language implemented using the Truffle API.
There is a newer version: 24.1.1
/*
 * Copyright (c) 2012, 2022, Oracle and/or its affiliates. All rights reserved.
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
 *
 * The Universal Permissive License (UPL), Version 1.0
 *
 * Subject to the condition set forth below, permission is hereby granted to any
 * person obtaining a copy of this software, associated documentation and/or
 * data (collectively the "Software"), free of charge and under any and all
 * copyright rights in the Software, and any and all patent rights owned or
 * freely licensable by each licensor hereunder covering either (i) the
 * unmodified Software as contributed to or provided by such licensor, or (ii)
 * the Larger Works (as defined below), to deal in both
 *
 * (a) the Software, and
 *
 * (b) any piece of software and/or hardware listed in the lrgrwrks.txt file if
 * one is included with the Software each a "Larger Work" to which the Software
 * is contributed by such licensors),
 *
 * without restriction, including without limitation the rights to copy, create
 * derivative works of, display, perform, and distribute the Software and make,
 * use, sell, offer for sale, import, export, have made, and have sold the
 * Software and the Larger Work(s), and to sublicense the foregoing rights on
 * either these or other terms.
 *
 * This license is subject to the following condition:
 *
 * The above copyright notice and either this complete permission notice or at a
 * minimum a reference to the UPL must be included in all copies or substantial
 * portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
 * SOFTWARE.
 */
package com.oracle.truffle.sl.nodes.local;

import com.oracle.truffle.api.CompilerDirectives;
import com.oracle.truffle.api.dsl.NodeField;
import com.oracle.truffle.api.dsl.Specialization;
import com.oracle.truffle.api.frame.VirtualFrame;
import com.oracle.truffle.api.instrumentation.StandardTags.ReadVariableTag;
import com.oracle.truffle.api.instrumentation.Tag;
import com.oracle.truffle.api.strings.TruffleString;
import com.oracle.truffle.sl.nodes.SLExpressionNode;
import com.oracle.truffle.sl.nodes.interop.NodeObjectDescriptor;

/**
 * Node to read a local variable from a function's {@link VirtualFrame frame}. The Truffle frame API
 * allows to store primitive values of all Java primitive types, and Object values. This means that
 * all SL types that are objects are handled by the {@link #readObject} method.
 * 
 * We use the primitive type only when the same primitive type is uses for all writes. If the local
 * variable is type-polymorphic, then the value is always stored as an Object, i.e., primitive
 * values are boxed. Even a mixture of {@code long} and {@code boolean} writes leads to both being
 * stored boxed.
 */
@NodeField(name = "slot", type = int.class)
public abstract class SLReadLocalVariableNode extends SLExpressionNode {

    /**
     * Returns the descriptor of the accessed local variable. The implementation of this method is
     * created by the Truffle DSL based on the {@link NodeField} annotation on the class.
     */
    protected abstract int getSlot();

    @Specialization(guards = "frame.isLong(getSlot())")
    protected long readLong(VirtualFrame frame) {
        /*
         * When the FrameSlotKind is Long, we know that only primitive long values have ever been
         * written to the local variable. So we do not need to check that the frame really contains
         * a primitive long value.
         */
        return frame.getLong(getSlot());
    }

    @Specialization(guards = "frame.isBoolean(getSlot())")
    protected boolean readBoolean(VirtualFrame frame) {
        return frame.getBoolean(getSlot());
    }

    @Specialization(replaces = {"readLong", "readBoolean"})
    protected Object readObject(VirtualFrame frame) {
        if (!frame.isObject(getSlot())) {
            /*
             * The FrameSlotKind has been set to Object, so from now on all writes to the local
             * variable will be Object writes. However, now we are in a frame that still has an old
             * non-Object value. This is a slow-path operation: we read the non-Object value, and
             * write it immediately as an Object value so that we do not hit this path again
             * multiple times for the same variable of the same frame.
             */
            CompilerDirectives.transferToInterpreter();
            Object result = frame.getValue(getSlot());
            frame.setObject(getSlot(), result);
            return result;
        }

        return frame.getObject(getSlot());
    }

    @Override
    public boolean hasTag(Class tag) {
        return tag == ReadVariableTag.class || super.hasTag(tag);
    }

    @Override
    public Object getNodeObject() {
        return NodeObjectDescriptor.readVariable((TruffleString) getRootNode().getFrameDescriptor().getSlotName(getSlot()));
    }
}