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51 lines
1.7 KiB
51 lines
1.7 KiB
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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