/*
* Copyright (c) 2013, 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.
*
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package org.graalvm.compiler.lir;
import java.util.ArrayList;
import org.graalvm.compiler.core.common.cfg.AbstractBlockBase;
import org.graalvm.compiler.lir.StandardOp.ImplicitNullCheck;
import org.graalvm.compiler.lir.StandardOp.NullCheck;
import org.graalvm.compiler.lir.gen.LIRGenerationResult;
import org.graalvm.compiler.lir.phases.PostAllocationOptimizationPhase;
import jdk.vm.ci.code.TargetDescription;
public final class NullCheckOptimizer extends PostAllocationOptimizationPhase {
@Override
protected void run(TargetDescription target, LIRGenerationResult lirGenRes, PostAllocationOptimizationContext context) {
LIR ir = lirGenRes.getLIR();
AbstractBlockBase<?>[] blocks = ir.codeEmittingOrder();
NullCheckOptimizer.foldNullChecks(ir, blocks, target.implicitNullCheckLimit);
}
private static void foldNullChecks(LIR ir, AbstractBlockBase<?>[] blocks, int implicitNullCheckLimit) {
for (AbstractBlockBase<?> block : blocks) {
if (block == null) {
continue;
}
ArrayList<LIRInstruction> list = ir.getLIRforBlock(block);
if (!list.isEmpty()) {
LIRInstruction lastInstruction = list.get(0);
for (int i = 0; i < list.size(); i++) {
LIRInstruction instruction = list.get(i);
if (instruction instanceof ImplicitNullCheck && lastInstruction instanceof NullCheck) {
NullCheck nullCheck = (NullCheck) lastInstruction;
ImplicitNullCheck implicitNullCheck = (ImplicitNullCheck) instruction;
if (implicitNullCheck.makeNullCheckFor(nullCheck.getCheckedValue(), nullCheck.getState(), implicitNullCheckLimit)) {
list.remove(i - 1);
if (i < list.size()) {
instruction = list.get(i);
}
}
}
lastInstruction = instruction;
}
}
}
}
}