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view graal/com.oracle.graal.bytecode/src/com/oracle/graal/bytecode/BytecodeStream.java @ 9000:c32173f91d0e
PhaseSuite
author | Roland Schatz <roland.schatz@oracle.com> |
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date | Thu, 11 Apr 2013 12:02:19 +0200 |
parents | 7ef66078d837 |
children | 1cde96b96673 |
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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.bytecode; /** * A utility class that makes iterating over bytecodes and reading operands simpler and less error * prone. For example, it handles the {@link Bytecodes#WIDE} instruction and wide variants of * instructions internally. */ public final class BytecodeStream { private final byte[] code; private int opcode; private int curBCI; private int nextBCI; /** * Creates a new {@code BytecodeStream} for the specified bytecode. * * @param code the array of bytes that contains the bytecode */ public BytecodeStream(byte[] code) { assert code != null; this.code = code; setBCI(0); } /** * Advances to the next bytecode. */ public void next() { setBCI(nextBCI); } /** * Gets the next bytecode index (no side-effects). * * @return the next bytecode index */ public int nextBCI() { return nextBCI; } /** * Gets the current bytecode index. * * @return the current bytecode index */ public int currentBCI() { return curBCI; } /** * Gets the bytecode index of the end of the code. * * @return the index of the end of the code */ public int endBCI() { return code.length; } /** * Gets the current opcode. This method will never return the {@link Bytecodes#WIDE WIDE} * opcode, but will instead return the opcode that is modified by the {@code WIDE} opcode. * * @return the current opcode; {@link Bytecodes#END} if at or beyond the end of the code */ public int currentBC() { if (opcode == Bytecodes.WIDE) { return Bytes.beU1(code, curBCI + 1); } else { return opcode; } } /** * Reads the index of a local variable for one of the load or store instructions. The WIDE * modifier is handled internally. * * @return the index of the local variable */ public int readLocalIndex() { // read local variable index for load/store if (opcode == Bytecodes.WIDE) { return Bytes.beU2(code, curBCI + 2); } return Bytes.beU1(code, curBCI + 1); } /** * Read the delta for an {@link Bytecodes#IINC} bytecode. * * @return the delta for the {@code IINC} */ public int readIncrement() { // read the delta for the iinc bytecode if (opcode == Bytecodes.WIDE) { return Bytes.beS2(code, curBCI + 4); } return Bytes.beS1(code, curBCI + 2); } /** * Read the destination of a {@link Bytecodes#GOTO} or {@code IF} instructions. * * @return the destination bytecode index */ public int readBranchDest() { // reads the destination for a branch bytecode if (opcode == Bytecodes.GOTO_W || opcode == Bytecodes.JSR_W) { return curBCI + Bytes.beS4(code, curBCI + 1); } else { return curBCI + Bytes.beS2(code, curBCI + 1); } } /** * Read a signed 4-byte integer from the bytecode stream at the specified bytecode index. * * @param bci the bytecode index * @return the integer value */ public int readInt(int bci) { // reads a 4-byte signed value return Bytes.beS4(code, bci); } /** * Reads an unsigned, 1-byte value from the bytecode stream at the specified bytecode index. * * @param bci the bytecode index * @return the byte */ public int readUByte(int bci) { return Bytes.beU1(code, bci); } /** * Reads a constant pool index for the current instruction. * * @return the constant pool index */ public char readCPI() { if (opcode == Bytecodes.LDC) { return (char) Bytes.beU1(code, curBCI + 1); } return (char) Bytes.beU2(code, curBCI + 1); } /** * Reads a constant pool index for an invokedynamic instruction. * * @return the constant pool index */ public int readCPI4() { assert opcode == Bytecodes.INVOKEDYNAMIC; return Bytes.beS4(code, curBCI + 1); } /** * Reads a signed, 1-byte value for the current instruction (e.g. BIPUSH). * * @return the byte */ public byte readByte() { return code[curBCI + 1]; } /** * Reads a signed, 2-byte short for the current instruction (e.g. SIPUSH). * * @return the short value */ public short readShort() { return (short) Bytes.beS2(code, curBCI + 1); } /** * Sets the bytecode index to the specified value. If {@code bci} is beyond the end of the * array, {@link #currentBC} will return {@link Bytecodes#END} and other methods may throw * {@link ArrayIndexOutOfBoundsException}. * * @param bci the new bytecode index */ public void setBCI(int bci) { curBCI = bci; if (curBCI < code.length) { opcode = Bytes.beU1(code, bci); assert opcode < Bytecodes.BREAKPOINT : "illegal bytecode"; nextBCI = bci + lengthOf(); } else { opcode = Bytecodes.END; nextBCI = curBCI; } } /** * Gets the length of the current bytecode. */ private int lengthOf() { int length = Bytecodes.lengthOf(opcode); if (length == 0) { switch (opcode) { case Bytecodes.TABLESWITCH: { return new BytecodeTableSwitch(this, curBCI).size(); } case Bytecodes.LOOKUPSWITCH: { return new BytecodeLookupSwitch(this, curBCI).size(); } case Bytecodes.WIDE: { int opc = Bytes.beU1(code, curBCI + 1); if (opc == Bytecodes.RET) { return 4; } else if (opc == Bytecodes.IINC) { return 6; } else { return 4; // a load or store bytecode } } default: throw new Error("unknown variable-length bytecode: " + opcode); } } return length; } }