| 摘要 |
An optimization method to be carried out within a digital computer under programmed control for eliminating or removing from a loop body alternate exit tests substantially of the form alpha i+ beta cond phi , where alpha , beta and phi are loop invariant expressions, i is the innermost loop index variable, and cond is one of the relational operators (=, NOTEQUAL ,>,>/=,<,</=). Each alternate exit test is compared to a list of elimination conditions. If an alternate exit test matches one of the elimination conditions, it is eliminated entirely from the loop body. If the alternate exit test cannot be eliminated, it is then compared to a list of restriction conditions. If the alternate exit test matches one of the restriction conditions, the loop index upper bound is modified if necessary and the alternate exit test is moved from inside to outside of the loop body. The resulting altered loop body is near optimum in terms of both the storage area utilized and the program execution time.
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