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/*
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* Copyright (c) 2012, 2018, Oracle and/or its affiliates. All rights reserved.
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* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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*
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* This code is free software; you can redistribute it and/or modify it
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* under the terms of the GNU General Public License version 2 only, as
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* published by the Free Software Foundation.
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*
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* This code is distributed in the hope that it will be useful, but WITHOUT
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* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
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* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
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* version 2 for more details (a copy is included in the LICENSE file that
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* accompanied this code).
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*
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* You should have received a copy of the GNU General Public License version
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* 2 along with this work; if not, write to the Free Software Foundation,
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* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
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*
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* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
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* or visit www.oracle.com if you need additional information or have any
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* questions.
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*/
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50858
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package org.graalvm.compiler.core.common.cfg;
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import static org.graalvm.compiler.core.common.cfg.AbstractBlockBase.BLOCK_ID_COMPARATOR;
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import java.util.ArrayList;
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import java.util.Collections;
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import java.util.List;
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public abstract class Loop<T extends AbstractBlockBase<T>> {
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private final Loop<T> parent;
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private final ArrayList<Loop<T>> children;
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private final int depth;
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private final int index;
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private final T header;
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private final ArrayList<T> blocks;
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private final ArrayList<T> exits;
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/**
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* Natural exits, ignoring LoopExitNodes.
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*
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* @see #getNaturalExits()
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*/
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private final ArrayList<T> naturalExits;
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protected Loop(Loop<T> parent, int index, T header) {
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this.parent = parent;
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if (parent != null) {
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this.depth = parent.getDepth() + 1;
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} else {
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this.depth = 1;
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}
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this.index = index;
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this.header = header;
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this.blocks = new ArrayList<>();
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this.children = new ArrayList<>();
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this.exits = new ArrayList<>();
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this.naturalExits = new ArrayList<>();
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}
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public abstract long numBackedges();
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@Override
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public String toString() {
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return "loop " + index + " depth " + getDepth() + (parent != null ? " outer " + parent.index : "");
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}
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public Loop<T> getParent() {
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return parent;
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}
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public List<Loop<T>> getChildren() {
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return children;
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}
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public int getDepth() {
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return depth;
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}
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public int getIndex() {
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return index;
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}
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public T getHeader() {
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return header;
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}
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public List<T> getBlocks() {
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return blocks;
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}
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/**
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* Returns the loop exits.
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*
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* This might be a conservative set: before framestate assignment it matches the LoopExitNodes
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* even if earlier blocks could be considered as exits. After framestate assignments, this is
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* the same as {@link #getNaturalExits()}.
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*
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* <p>
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* LoopExitNodes are inserted in the control-flow during parsing and are natural exits: they are
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* the earliest block at which we are guaranteed to have exited the loop. However, after some
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* transformations of the graph, the natural exit might go up but the LoopExitNodes are not
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* updated.
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* </p>
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*
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* <p>
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* For example in:
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*
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* <pre>
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* for (int i = 0; i < N; i++) {
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* if (c) {
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* // Block 1
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* if (dummy) {
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* // ...
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* } else {
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* // ...
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* }
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* if (b) {
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* continue;
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* } else {
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* // Block 2
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* // LoopExitNode
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* break;
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* }
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* }
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* }
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* </pre>
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*
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* After parsing, the natural exits match the LoopExitNode: Block 2 is a natural exit and has a
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* LoopExitNode. If the {@code b} condition gets canonicalized to {@code false}, the natural
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* exit moves to Block 1 while the LoopExitNode remains in Block 2. In such a scenario,
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* {@code getLoopExits()} will contain block 2 while {@link #getNaturalExits()} will contain
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* block 1.
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*
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*
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* @see #getNaturalExits()
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*/
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public List<T> getLoopExits() {
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return exits;
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}
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public boolean isLoopExit(T block) {
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assert isSorted(exits);
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return Collections.binarySearch(exits, block, BLOCK_ID_COMPARATOR) >= 0;
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}
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/**
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* Returns the natural exit points: these are the earliest block that are guaranteed to never
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* reach a back-edge.
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*
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* This can not be used in the context of preserving or using loop-closed form.
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*
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* @see #getLoopExits()
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*/
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public ArrayList<T> getNaturalExits() {
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return naturalExits;
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}
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public boolean isNaturalExit(T block) {
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assert isSorted(naturalExits);
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return Collections.binarySearch(naturalExits, block, BLOCK_ID_COMPARATOR) >= 0;
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}
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private static <T extends AbstractBlockBase<T>> boolean isSorted(List<T> list) {
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int lastId = Integer.MIN_VALUE;
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for (AbstractBlockBase<?> block : list) {
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if (block.getId() < lastId) {
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return false;
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}
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lastId = block.getId();
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}
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return true;
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}
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/**
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* Determines if one loop is a transitive parent of another loop.
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*
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* @param childLoop The loop for which parentLoop might be a transitive parent loop.
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* @param parentLoop The loop which might be a transitive parent loop of child loop.
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* @return {@code true} if parentLoop is a (transitive) parent loop of childLoop, {@code false}
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* otherwise
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*/
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public static <T extends AbstractBlockBase<T>> boolean transitiveParentLoop(Loop<T> childLoop, Loop<T> parentLoop) {
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Loop<T> curr = childLoop;
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while (curr != null) {
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if (curr == parentLoop) {
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return true;
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}
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curr = curr.getParent();
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}
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return false;
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}
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@Override
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public int hashCode() {
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return index + depth * 31;
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}
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@Override
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public boolean equals(Object obj) {
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return super.equals(obj);
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}
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}
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