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109 lines
4.1 KiB
109 lines
4.1 KiB
/*
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* CreateIfStatements (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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public class CreateIfStatements extends FlowTransformation
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implements Transformation {
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public InstructionHeader transform(InstructionHeader ifgoto) {
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if (ifgoto.getFlowType() != ifgoto.IFGOTO ||
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ifgoto.nextInstruction == null ||
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ifgoto.getSuccessors()[1].getAddress() <=
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ifgoto.getSuccessors()[0].getAddress())
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return null;
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/* elseBlock points to the first instruction of the
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* elseBlock or is null if the else block is empty.
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* next points to the next instruction after this block
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* or is null, if this if is the last instruction in
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* this block.
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*/
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InstructionHeader elseBlock = null, next = null;
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if (ifgoto.outer != ifgoto.successors[1].outer) {
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if (ifgoto.outer.getEndBlock() != ifgoto.successors[1].getShadow())
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/* This doesn't seem to be an if but a if-break
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*/
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return null;
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/* This is an if without else that goes to the end
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* of the current block. May be this was a continue,
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* but who would know it?
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*
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* If you like breaks and continues more than ifs,
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* simply do the break transformation before the
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* if transformation.
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*/
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next = null;
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} else {
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/* This is a normal if, let us first assume, that there is
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* no else part. Then end is successors[1], but that may
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* be a while loop, so unoptimized it...
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*/
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next = UnoptimizeWhileLoops(ifgoto.successors[1]);
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if (next != ifgoto.successors[1]) {
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ifgoto.successors[1].predecessors.removeElement(ifgoto);
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ifgoto.successors[1] = next;
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ifgoto.successors[1].predecessors.addElement(ifgoto);
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}
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/* next.prevInstruction is the end of the `then' block.
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* If this a goto statement that jumps downward, this is
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* probably an `if-then-else'.
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*/
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InstructionHeader thenEnd = next.prevInstruction;
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if (thenEnd.flowType == thenEnd.GOTO) {
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if (thenEnd.successors[0].outer == next.outer &&
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thenEnd.successors[0].addr >= next.addr) {
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/* this is a normal if-then-else that is
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* fully contained in this block.
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*/
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elseBlock = next;
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next = UnoptimizeWhileLoops(thenEnd.successors[0]);
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} else if (thenEnd.successors[0].getShadow() ==
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ifgoto.outer.getEndBlock()) {
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/* this is a normal if-then-else that goes
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* to the end of the block.
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*
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* Again this may also be a continue/break statement,
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* but again, who knows.
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*/
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elseBlock = next;
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next = null;
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}
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}
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}
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/* This was all, the rest is done in the constructor of
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* IfInstructionHeader.
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*/
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if(Decompiler.isVerbose)
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System.err.print("i");
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return new IfInstructionHeader
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(ifgoto, elseBlock, next);
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}
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}
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