Mercurial > hg > graal-jvmci-8
view graal/com.oracle.graal.lir/src/com/oracle/graal/lir/ControlFlowOptimizer.java @ 14787:6ce74db1c9fb
Use List<T> instead of Iterable<T> in AbstractBlock to (temporary) allow editing.
author | Josef Eisl <josef.eisl@jku.at> |
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date | Wed, 12 Mar 2014 13:38:12 +0100 |
parents | a6595f1b55b0 |
children | a8723f1ff542 |
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/* * Copyright (c) 2009, 2011, 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 com.oracle.graal.lir; import static com.oracle.graal.lir.LIR.*; import java.util.*; import com.oracle.graal.debug.*; import com.oracle.graal.nodes.cfg.*; /** * This class performs basic optimizations on the control flow graph after LIR generation. */ public final class ControlFlowOptimizer { /** * Performs control flow optimizations on the given LIR graph. */ public static <T extends AbstractBlock<T>> void optimize(LIR lir, List<T> codeEmittingOrder) { ControlFlowOptimizer.deleteEmptyBlocks(lir, codeEmittingOrder); } private ControlFlowOptimizer() { } private static final DebugMetric BLOCKS_DELETED = Debug.metric("BlocksDeleted"); /** * Checks whether a block can be deleted. Only blocks with exactly one successor and an * unconditional branch to this successor are eligable. * * @param block the block checked for deletion * @return whether the block can be deleted */ private static boolean canDeleteBlock(LIR lir, AbstractBlock<?> block) { if (block.getSuccessorCount() != 1 || block.getPredecessorCount() == 0 || block.getSuccessors().iterator().next() == block) { return false; } List<LIRInstruction> instructions = lir.lir(block); assert instructions.size() >= 2 : "block must have label and branch"; assert instructions.get(0) instanceof StandardOp.LabelOp : "first instruction must always be a label"; assert instructions.get(instructions.size() - 1) instanceof StandardOp.JumpOp : "last instruction must always be a branch"; assert ((StandardOp.JumpOp) instructions.get(instructions.size() - 1)).destination().label() == ((StandardOp.LabelOp) lir.lir(block.getSuccessors().iterator().next()).get(0)).getLabel() : "branch target must be the successor"; // Block must have exactly one successor. return instructions.size() == 2 && !instructions.get(instructions.size() - 1).hasState() && !block.isExceptionEntry(); } private static void alignBlock(LIR lir, AbstractBlock<?> block) { if (!block.isAligned()) { block.setAlign(true); List<LIRInstruction> instructions = lir.lir(block); assert instructions.get(0) instanceof StandardOp.LabelOp : "first instruction must always be a label"; StandardOp.LabelOp label = (StandardOp.LabelOp) instructions.get(0); instructions.set(0, new StandardOp.LabelOp(label.getLabel(), true)); } } private static <T extends AbstractBlock<T>> void deleteEmptyBlocks(LIR lir, List<T> blocks) { assert verifyBlocks(lir, blocks); Iterator<T> iterator = blocks.iterator(); while (iterator.hasNext()) { T block = iterator.next(); if (canDeleteBlock(lir, block)) { // adjust successor and predecessor lists T other = block.getSuccessors().iterator().next(); for (AbstractBlock<T> pred : block.getPredecessors()) { Collections.replaceAll(pred.getSuccessors(), block, other); } for (int i = 0; i < other.getPredecessorCount(); i++) { if (other.getPredecessors().get(i) == block) { other.getPredecessors().remove(i); other.getPredecessors().addAll(i, block.getPredecessors()); } } block.getSuccessors().clear(); block.getPredecessors().clear(); if (block.isAligned()) { alignBlock(lir, other); } BLOCKS_DELETED.increment(); iterator.remove(); } } assert verifyBlocks(lir, blocks); } }