/*
 * Copyright (c) 2015, 2018, 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 org.graalvm.compiler.lir.amd64.phases;

import static org.graalvm.compiler.lir.phases.LIRPhase.Options.LIROptimization;

import java.util.ArrayList;
import java.util.Collections;
import java.util.List;

import org.graalvm.compiler.core.common.cfg.AbstractBlockBase;
import org.graalvm.compiler.debug.CounterKey;
import org.graalvm.compiler.debug.DebugContext;
import org.graalvm.compiler.lir.LIR;
import org.graalvm.compiler.lir.LIRInstruction;
import org.graalvm.compiler.lir.RedundantMoveElimination;
import org.graalvm.compiler.lir.amd64.AMD64Move.AMD64MultiStackMove;
import org.graalvm.compiler.lir.amd64.AMD64Move.AMD64StackMove;
import org.graalvm.compiler.lir.gen.LIRGenerationResult;
import org.graalvm.compiler.lir.phases.PostAllocationOptimizationPhase;
import org.graalvm.compiler.options.NestedBooleanOptionKey;
import org.graalvm.compiler.options.Option;
import org.graalvm.compiler.options.OptionType;

import jdk.vm.ci.code.Register;
import jdk.vm.ci.code.TargetDescription;
import jdk.vm.ci.meta.AllocatableValue;
import jdk.vm.ci.meta.Value;

Replaces sequential AMD64StackMoves of the same type with a single AMD64MultiStackMove to avoid storing/restoring the scratch register multiple times. Note: this phase must be inserted after RedundantMoveElimination phase because AMD64MultiStackMove are not probably detected.
/** * Replaces sequential {@link AMD64StackMove}s of the same type with a single * {@link AMD64MultiStackMove} to avoid storing/restoring the scratch register multiple times. * * Note: this phase must be inserted <b>after</b> {@link RedundantMoveElimination} phase because * {@link AMD64MultiStackMove} are not probably detected. */
public class StackMoveOptimizationPhase extends PostAllocationOptimizationPhase { public static class Options { // @formatter:off @Option(help = "", type = OptionType.Debug) public static final NestedBooleanOptionKey LIROptStackMoveOptimizer = new NestedBooleanOptionKey(LIROptimization, true); // @formatter:on } private static final CounterKey eliminatedBackup = DebugContext.counter("StackMoveOptimizer[EliminatedScratchBackupRestore]"); @Override protected void run(TargetDescription target, LIRGenerationResult lirGenRes, PostAllocationOptimizationContext context) { LIR lir = lirGenRes.getLIR(); DebugContext debug = lir.getDebug(); for (AbstractBlockBase<?> block : lir.getControlFlowGraph().getBlocks()) { ArrayList<LIRInstruction> instructions = lir.getLIRforBlock(block); new Closure().process(debug, instructions); } } private static class Closure { private static final int NONE = -1; private int begin = NONE; private Register reg = null; private List<AllocatableValue> dst; private List<Value> src; private AllocatableValue slot; private boolean removed = false; public void process(DebugContext debug, List<LIRInstruction> instructions) { for (int i = 0; i < instructions.size(); i++) { LIRInstruction inst = instructions.get(i); if (isStackMove(inst)) { AMD64StackMove move = asStackMove(inst); if (reg != null && !reg.equals(move.getScratchRegister())) { // end of trace & start of new replaceStackMoves(debug, instructions); } // lazy initialize if (dst == null) { assert src == null; dst = new ArrayList<>(); src = new ArrayList<>(); } dst.add(move.getResult()); src.add(move.getInput()); if (begin == NONE) { // trace begin begin = i; reg = move.getScratchRegister(); slot = move.getBackupSlot(); } } else if (begin != NONE) { // end of trace replaceStackMoves(debug, instructions); } } // remove instructions if (removed) { instructions.removeAll(Collections.singleton(null)); } } private void replaceStackMoves(DebugContext debug, List<LIRInstruction> instructions) { int size = dst.size(); if (size > 1) { AMD64MultiStackMove multiMove = new AMD64MultiStackMove(dst.toArray(new AllocatableValue[size]), src.toArray(new AllocatableValue[size]), reg, slot); // replace first instruction instructions.set(begin, multiMove); // and null out others Collections.fill(instructions.subList(begin + 1, begin + size), null); // removed removed = true; eliminatedBackup.add(debug, size - 1); } // reset dst.clear(); src.clear(); begin = NONE; reg = null; slot = null; } } private static AMD64StackMove asStackMove(LIRInstruction inst) { assert isStackMove(inst); return (AMD64StackMove) inst; } private static boolean isStackMove(LIRInstruction inst) { return inst instanceof AMD64StackMove; } }