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70 lines
2.4 KiB
70 lines
2.4 KiB
/*
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* CombineIfGotoExpressions (c) 1998 Jochen Hoenicke
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*
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* You may distribute under the terms of the GNU General Public License.
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*
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* IN NO EVENT SHALL JOCHEN HOENICKE BE LIABLE TO ANY PARTY FOR DIRECT,
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* INDIRECT, SPECIAL, INCIDENTAL, OR CONSEQUENTIAL DAMAGES ARISING OUT OF
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* THE USE OF THIS SOFTWARE AND ITS DOCUMENTATION, EVEN IF JOCHEN HOENICKE
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* HAS BEEN ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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*
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* JOCHEN HOENICKE SPECIFICALLY DISCLAIMS ANY WARRANTIES, INCLUDING, BUT NOT
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* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A
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* PARTICULAR PURPOSE. THE SOFTWARE PROVIDED HEREUNDER IS ON AN "AS IS"
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* BASIS, AND JOCHEN HOENICKE HAS NO OBLIGATION TO PROVIDE MAINTENANCE,
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* SUPPORT, UPDATES, ENHANCEMENTS, OR MODIFICATIONS.
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*
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* $Id$
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*/
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package jode;
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import java.util.Vector;
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public class CombineIfGotoExpressions implements Transformation{
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public InstructionHeader transform(InstructionHeader ih2) {
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InstructionHeader ih1;
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Expression[] e;
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int operator;
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try {
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if (ih2.getFlowType() != ih2.IFGOTO)
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return null;
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InstructionHeader[] dests2 = ih2.getSuccessors();
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/* if ih2.getSimpleUniquePredecessor.getOperator().isVoid() XXX */
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Vector predec = ih2.getPredecessors();
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if (predec.size() != 1)
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return null;
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ih1 = (InstructionHeader) predec.elementAt(0);
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if (ih1.getFlowType() != ih1.IFGOTO)
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return null;
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InstructionHeader[] dests1 = ih1.getSuccessors();
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if (dests1[0] != ih2)
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return null;
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if (dests1[1] == dests2[0]) {
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e = new Expression[2];
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operator = Operator.LOG_AND_OP;
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e[1] = (Expression)ih2.getInstruction();
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e[0] = ((Expression)ih1.getInstruction()).negate();
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} else if (dests1[1] == dests2[1]) {
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e = new Expression[2];
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operator = Operator.LOG_OR_OP;
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e[1] = (Expression)ih2.getInstruction();
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e[0] = (Expression)ih1.getInstruction();
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} else
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return null;
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} catch (ClassCastException ex) {
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return null;
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} catch (NullPointerException ex) {
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return null;
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}
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Expression cond =
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new Expression(new BinaryOperator(MyType.tBoolean, operator), e);
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return ih1.combineConditional(cond);
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}
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}
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