Extracting the Parallelism in Program with non-structured statements

Non-structured programs are diicult to parallelize. First, the scope of the non-structured statements may interact and the execution trajectories can overlap, preventing the unique determination of the scope of a control statement. Second, even if the scope of a non-structured statement is determined and is converted into a while loop, this while loop is still diicult to parallelize due to the loop carried dependencies of the control variables. In this paper, a method of program structuring is proposed, which is based on a hammock transformation of the ow graph, and converts non-structured statements into block if-statements and while loops. Furthermore, an algorithm was developed to transform a common type of while loops into do loops. The technique works for while loops of which the control variables appear as a linear recurrence relation. As a result, the loop carried dependencies generated by the control variables are removed. If there are no other loop carried dependencies, the do loop may then be converted into a doall loop. The algorithm was used to test and convert a significant number of while loops into doall loops for a suite of well-known numerical algorithms. Abstract Non-structured programs are diicult to parallelize. First, the scope of the non-structured statements may interact and the execution trajectories can overlap, preventing the unique determination of the scope of a control statement. Second, even if the scope of a non-structured statement is determined and is converted into a while loop, this while loop is still diicult to parallelize due to the loop carried dependencies of the control variables. In this paper, a method of program structuring is proposed, which is based on a hammock transformation of the ow graph, and converts non-structured statements into block if-statements and while loops. Furthermore, an algorithm was developed to transform a common type of while loops into do loops. The technique works for while loops of which the control variables appear as a linear recurrence relation. As a result, the loop carried dependencies generated by the control variables are removed. If there are no other loop carried dependencies, the do loop may then be converted into a doall loop. The algorithm was used to test and convert a significant number of while loops into doall loops for a suite of well-known numerical algorithms.