question: public void insertTwin ( Instruction inst , Instruction twin ) { ListIterator < GCIRMapElement > iter = list . listIterator ( ) ; while ( iter . hasNext ( ) ) { GCIRMapElement newPtr = iter . next ( ) ; if ( newPtr . getInstruction ( ) == inst ) { iter . add ( newPtr . createTwin ( twin ) ) ; return ; } } throw new OptimizingCompilerException ( "GCIRMap.createTwin: " + inst + " not found" ) ; }
target:  This method inserts an entry for a "twin" instruction immediately after the original entry. If the instruction is not found in the GC Map an exception is thrown.