001/*
002 * Copyright (c) 2013, Oracle and/or its affiliates. All rights reserved.
003 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
004 *
005 * This code is free software; you can redistribute it and/or modify it
006 * under the terms of the GNU General Public License version 2 only, as
007 * published by the Free Software Foundation.
008 *
009 * This code is distributed in the hope that it will be useful, but WITHOUT
010 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
011 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
012 * version 2 for more details (a copy is included in the LICENSE file that
013 * accompanied this code).
014 *
015 * You should have received a copy of the GNU General Public License version
016 * 2 along with this work; if not, write to the Free Software Foundation,
017 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
018 *
019 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
020 * or visit www.oracle.com if you need additional information or have any
021 * questions.
022 */
023package com.oracle.graal.lir;
024
025import java.util.*;
026
027import jdk.internal.jvmci.code.*;
028
029import com.oracle.graal.compiler.common.cfg.*;
030import com.oracle.graal.lir.StandardOp.ImplicitNullCheck;
031import com.oracle.graal.lir.StandardOp.NullCheck;
032import com.oracle.graal.lir.gen.*;
033import com.oracle.graal.lir.phases.*;
034
035public final class NullCheckOptimizer extends PostAllocationOptimizationPhase {
036
037    @Override
038    protected <B extends AbstractBlockBase<B>> void run(TargetDescription target, LIRGenerationResult lirGenRes, List<B> codeEmittingOrder, List<B> linearScanOrder,
039                    BenchmarkCounterFactory counterFactory) {
040        LIR ir = lirGenRes.getLIR();
041        List<? extends AbstractBlockBase<?>> blocks = ir.codeEmittingOrder();
042        NullCheckOptimizer.foldNullChecks(ir, blocks, target.implicitNullCheckLimit);
043    }
044
045    private static void foldNullChecks(LIR ir, List<? extends AbstractBlockBase<?>> blocks, int implicitNullCheckLimit) {
046        for (AbstractBlockBase<?> block : blocks) {
047            List<LIRInstruction> list = ir.getLIRforBlock(block);
048
049            if (!list.isEmpty()) {
050
051                LIRInstruction lastInstruction = list.get(0);
052                for (int i = 0; i < list.size(); i++) {
053                    LIRInstruction instruction = list.get(i);
054
055                    if (instruction instanceof ImplicitNullCheck && lastInstruction instanceof NullCheck) {
056                        NullCheck nullCheck = (NullCheck) lastInstruction;
057                        ImplicitNullCheck implicitNullCheck = (ImplicitNullCheck) instruction;
058                        if (implicitNullCheck.makeNullCheckFor(nullCheck.getCheckedValue(), nullCheck.getState(), implicitNullCheckLimit)) {
059                            list.remove(i - 1);
060                            if (i < list.size()) {
061                                instruction = list.get(i);
062                            }
063                        }
064                    }
065                    lastInstruction = instruction;
066                }
067            }
068        }
069    }
070
071}