1 /* 2 * Copyright (c) 2011, 2011, Oracle and/or its affiliates. All rights reserved. 3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. 4 * 5 * This code is free software; you can redistribute it and/or modify it 6 * under the terms of the GNU General Public License version 2 only, as 7 * published by the Free Software Foundation. 8 * 9 * This code is distributed in the hope that it will be useful, but WITHOUT 10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or 11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License 12 * version 2 for more details (a copy is included in the LICENSE file that 13 * accompanied this code). 14 * 15 * You should have received a copy of the GNU General Public License version 16 * 2 along with this work; if not, write to the Free Software Foundation, 17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. 18 * 19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA 20 * or visit www.oracle.com if you need additional information or have any 21 * questions. 22 */ 23 package org.graalvm.compiler.lir; 24 25 import org.graalvm.compiler.asm.Label; 26 import org.graalvm.compiler.core.common.cfg.AbstractBlockBase; 27 import org.graalvm.compiler.lir.StandardOp.BranchOp; 28 import org.graalvm.compiler.lir.StandardOp.JumpOp; 29 30 /** 31 * LIR instructions such as {@link JumpOp} and {@link BranchOp} need to reference their target 32 * {@link AbstractBlockBase}. However, direct references are not possible since the control flow 33 * graph (and therefore successors lists) can be changed by optimizations - and fixing the 34 * instructions is error prone. Therefore, we represent an edge to block B from block A via the 35 * tuple {@code (A, 36 * successor-index-of-B)}. That is, indirectly by storing the index into the successor list of A. 37 * Note therefore that the successor list cannot be re-ordered. 38 */ 39 public final class LabelRef { 40 41 private final LIR lir; 42 private final AbstractBlockBase<?> block; 43 private final int suxIndex; 44 45 /** 46 * Returns a new reference to a successor of the given block. 47 * 48 * @param block The base block that contains the successor list. 49 * @param suxIndex The index of the successor. 50 * @return The newly created label reference. 51 */ 52 public static LabelRef forSuccessor(final LIR lir, final AbstractBlockBase<?> block, final int suxIndex) { 53 return new LabelRef(lir, block, suxIndex); 54 } 55 56 /** 57 * Returns a new reference to a successor of the given block. 58 * 59 * @param block The base block that contains the successor list. 60 * @param suxIndex The index of the successor. 61 */ 62 private LabelRef(final LIR lir, final AbstractBlockBase<?> block, final int suxIndex) { 63 this.lir = lir; 64 this.block = block; 65 this.suxIndex = suxIndex; 66 } 67 68 public AbstractBlockBase<?> getSourceBlock() { 69 return block; 70 } 71 72 public AbstractBlockBase<?> getTargetBlock() { 73 return block.getSuccessors()[suxIndex]; 74 } 75 76 public Label label() { 77 return ((StandardOp.LabelOp) lir.getLIRforBlock(getTargetBlock()).get(0)).getLabel(); 78 } 79 80 @Override 81 public String toString() { 82 return getSourceBlock() + " -> " + (suxIndex < block.getSuccessors().length ? getTargetBlock() : "?"); 83 } 84 }