com.oracle.truffle.sl.nodes.controlflow.SLBlockNode Maven / Gradle / Ivy

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 * (a) the Software, and
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package com.oracle.truffle.sl.nodes.controlflow;

import java.util.Arrays;
import java.util.Collections;
import java.util.List;

import com.oracle.truffle.api.frame.VirtualFrame;
import com.oracle.truffle.api.nodes.BlockNode;
import com.oracle.truffle.api.nodes.BlockNode.ElementExecutor;
import com.oracle.truffle.api.nodes.ControlFlowException;
import com.oracle.truffle.api.nodes.ExplodeLoop;
import com.oracle.truffle.api.nodes.NodeInfo;
import com.oracle.truffle.sl.nodes.SLStatementNode;

/**
 * A statement node that just executes a list of other statements.
 */
@NodeInfo(shortName = "block", description = "The node implementing a source code block")
public final class SLBlockNode extends SLStatementNode implements BlockNode.ElementExecutor {

    /**
     * The block of child nodes. Using the block node allows Truffle to split the block into
     * multiple groups for compilation if the method is too big. This is an optional API.
     * Alternatively, you may just use your own block node, with a
     * {@link com.oracle.truffle.api.nodes.Node.Children @Children} field. However, this prevents
     * Truffle from compiling big methods, so these methods might fail to compile with a compilation
     * bailout.
     */
    @Child private BlockNode block;

    public SLBlockNode(SLStatementNode[] bodyNodes) {
        /*
         * Truffle block nodes cannot be empty, that is why we just set the entire block to null if
         * there are no elements. This is good practice as it safes memory.
         */
        this.block = bodyNodes.length > 0 ? BlockNode.create(bodyNodes, this) : null;
    }

    /**
     * Execute all block statements. The block node makes sure that {@link ExplodeLoop full
     * unrolling} of the loop is triggered during compilation. This allows the
     * {@link SLStatementNode#executeVoid} method of all children to be inlined.
     */
    @Override
    public void executeVoid(VirtualFrame frame) {
        if (this.block != null) {
            this.block.executeVoid(frame, BlockNode.NO_ARGUMENT);
        }
    }

    public List getStatements() {
        if (block == null) {
            return Collections.emptyList();
        }
        return Collections.unmodifiableList(Arrays.asList(block.getElements()));
    }

    /**
     * Truffle nodes don't have a fixed execute signature. The {@link ElementExecutor} interface
     * tells the framework how block element nodes should be executed. The executor allows to add a
     * custom exception handler for each element, e.g. to handle a specific
     * {@link ControlFlowException} or to pass a customizable argument, that allows implement
     * startsWith semantics if needed. For SL we don't need to pass any argument as we just have
     * plain block nodes, therefore we pass {@link BlockNode#NO_ARGUMENT}. In our case the executor
     * does not need to remember any state so we reuse a singleton instance.
     */
    public void executeVoid(VirtualFrame frame, SLStatementNode node, int index, int argument) {
        node.executeVoid(frame);
    }

}