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103 lines
3.8 KiB
103 lines
3.8 KiB
/* CombineIfGotoExpressions Copyright (C) 1998-2002 Jochen Hoenicke.
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU Lesser General Public License as published by
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* the Free Software Foundation; either version 2, or (at your option)
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* any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU Lesser General Public License
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* along with this program; see the file COPYING.LESSER. If not, write to
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* the Free Software Foundation, 675 Mass Ave, Cambridge, MA 02139, USA.
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*
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* $Id$
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*/
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package net.sf.jode.flow;
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import net.sf.jode.expr.*;
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import net.sf.jode.type.Type;
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public class CombineIfGotoExpressions {
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public static boolean transform(ConditionalBlock cb,
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StructuredBlock last) {
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if (cb.jump == null
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|| !(last.outer instanceof SequentialBlock))
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return false;
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SequentialBlock sequBlock = (SequentialBlock) cb.outer;
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Expression firstCond, secondCond;
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secondCond = cb.getInstruction();
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Expression lastCombined = secondCond;
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while (sequBlock.subBlocks[0] instanceof InstructionBlock) {
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InstructionBlock ib =
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(InstructionBlock) sequBlock.subBlocks[0];
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if (!(sequBlock.outer instanceof SequentialBlock))
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return false;
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Expression expr = ib.getInstruction();
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if (!(expr instanceof CombineableOperator)
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|| (lastCombined.canCombine((CombineableOperator)expr)
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+ secondCond.canCombine((CombineableOperator)expr) <= 0))
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/* Tricky, the above is true, iff one of the two
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* Expressions conflict, or both fail. */
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return false;
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lastCombined = expr;
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sequBlock = (SequentialBlock) sequBlock.outer;
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}
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if (sequBlock.subBlocks[0] instanceof ConditionalBlock) {
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ConditionalBlock cbprev =
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(ConditionalBlock) sequBlock.subBlocks[0];
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Jump prevJump = cbprev.trueBlock.jump;
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int operator;
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if (prevJump.destination == cb.jump.destination) {
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operator = BinaryOperator.LOG_AND_OP;
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firstCond = cbprev.getInstruction().negate();
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} else if (prevJump.destination == cb.trueBlock.jump.destination) {
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operator = BinaryOperator.LOG_OR_OP;
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firstCond = cbprev.getInstruction();
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} else
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return false;
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/* We have changed some instructions above. We may never
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* return with a failure now.
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*/
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sequBlock = (SequentialBlock) cb.outer;
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while (sequBlock.subBlocks[0] instanceof InstructionBlock) {
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/* Now combine the expression. Everything should
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* succeed, because we have checked above. */
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InstructionBlock ib =
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(InstructionBlock) sequBlock.subBlocks[0];
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Expression expr = ib.getInstruction();
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secondCond = secondCond.combine((CombineableOperator) expr);
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sequBlock = (SequentialBlock) sequBlock.outer;
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}
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cb.flowBlock.removeSuccessor(prevJump);
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prevJump.prev.removeJump();
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Expression cond = new BinaryOperator(Type.tBoolean, operator)
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.addOperand(secondCond).addOperand(firstCond);
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cb.setInstruction(cond);
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cb.moveDefinitions(sequBlock, last);
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last.replace(sequBlock);
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return true;
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}
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return false;
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}
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}
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