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119 lines
3.6 KiB
119 lines
3.6 KiB
/* CreateExpression 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.GlobalOptions;
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import net.sf.jode.expr.*;
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/**
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* This transformation creates expressions. It transforms
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* <pre>
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* Sequ[expr_1, Sequ[expr_2, ..., Sequ[expr_n, op] ...]]
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* </pre>
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* to
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* <pre>
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* expr(op, [ expr_1, ..., expr_n ])
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* </pre>
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*/
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public class CreateExpression {
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/**
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* This does the transformation.
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* @return true if flow block was simplified.
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*/
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public static boolean transform(InstructionContainer ic,
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StructuredBlock last) {
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int params = ic.getInstruction().getFreeOperandCount();
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if (params == 0)
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return false;
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if (!(last.outer instanceof SequentialBlock))
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return false;
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SequentialBlock sequBlock = (SequentialBlock)last.outer;
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/* First check if Expression can be created, but do nothing yet.
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*/
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Expression lastExpression = ic.getInstruction();
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while (true) {
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if (!(sequBlock.subBlocks[0] instanceof InstructionBlock))
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return false;
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Expression expr =
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((InstructionBlock) sequBlock.subBlocks[0]).getInstruction();
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if (!expr.isVoid())
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break;
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if (expr.getFreeOperandCount() > 0
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|| !(expr instanceof CombineableOperator)
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|| lastExpression.canCombine((CombineableOperator) expr) <= 0)
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return false;
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/* Hmm, we should really set lastExpression to
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* lastExpression.combine(expr), but that may change the
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* expressions :-( XXX
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*
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* We do a conservative approach and check if there are
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* no possible side effects with the skipped expressions.
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* Theoretically we would only have to check expressions,
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* that are combined at an earlier point.
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*/
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SequentialBlock block = sequBlock;
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while (block != last.outer) {
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block = (SequentialBlock) block.subBlocks[1];
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if (((InstructionBlock)block.subBlocks[0])
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.getInstruction().hasSideEffects(expr))
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return false;
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}
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if (!(sequBlock.outer instanceof SequentialBlock))
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return false;
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sequBlock = (SequentialBlock) sequBlock.outer;
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}
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/* Now, do the combination. Everything must succeed now.
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*/
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sequBlock = (SequentialBlock) last.outer;
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lastExpression = ic.getInstruction();
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while (true) {
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Expression expr =
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((InstructionBlock) sequBlock.subBlocks[0]).getInstruction();
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if (!expr.isVoid()) {
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lastExpression = lastExpression.addOperand(expr);
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break;
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}
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lastExpression = lastExpression.combine
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((CombineableOperator) expr);
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sequBlock = (SequentialBlock)sequBlock.outer;
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}
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if (GlobalOptions.verboseLevel > 0
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&& lastExpression.getFreeOperandCount() == 0)
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GlobalOptions.err.print('x');
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ic.setInstruction(lastExpression);
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ic.moveDefinitions(sequBlock, last);
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last.replace(sequBlock);
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return true;
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}
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}
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