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85 lines
2.9 KiB
85 lines
2.9 KiB
/*
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* RemoveEmpty (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.flow;
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import jode.Instruction;
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import jode.NopOperator;
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public class RemoveEmpty implements Transformation {
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public boolean transform (FlowBlock fb) {
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return (removeNop(fb) || removeEmpty(fb));
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}
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public boolean removeNop(FlowBlock flow) {
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StructuredBlock block;
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SequentialBlock sequBlock;
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Instruction instr;
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try {
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block = flow.lastModified;
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if (!(((InstructionContainer)block).getInstruction()
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instanceof NopOperator))
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return false;
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sequBlock = (SequentialBlock)block.outer;
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if (sequBlock.getSubBlocks()[1] != block)
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return false;
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InstructionBlock prev =
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(InstructionBlock) sequBlock.getSubBlocks()[0];
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if (prev.jump != null)
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return false;
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instr = (Instruction) prev.getInstruction();
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} catch (NullPointerException ex) {
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return false;
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} catch (ClassCastException ex) {
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return false;
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}
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((InstructionContainer)block).setInstruction(instr);
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block.replace(sequBlock, block);
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flow.lastModified = block;
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return true;
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}
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public boolean removeEmpty(FlowBlock flow) {
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StructuredBlock lastBlock = flow.lastModified;
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if (lastBlock instanceof EmptyBlock &&
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lastBlock.outer instanceof SequentialBlock &&
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lastBlock.outer.getSubBlocks()[1] == lastBlock) {
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StructuredBlock block = lastBlock.outer.getSubBlocks()[0];
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block.replace(block.outer, block);
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if (block.jump == null)
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block.moveJump(lastBlock);
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else
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lastBlock.removeJump();
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flow.lastModified = block;
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return true;
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}
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if (lastBlock.outer instanceof SequentialBlock &&
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lastBlock.outer.getSubBlocks()[0] instanceof EmptyBlock &&
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lastBlock.outer.getSubBlocks()[0].jump == null) {
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lastBlock.replace(lastBlock.outer, lastBlock);
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flow.lastModified = lastBlock;
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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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