Abstract: GCC compiler is an open source compiler system which has won favour among many researchers,however,it is only able to analyze the dependence of perfect nested loop.In order to efficiently explore the granularity parallelism of nested loop,we deeply analyzed the data dependence of GCC5.1 and put forward a dependence testing method of handling branch nested loop.At first,the branch nested loop is recognized.Then,the relationship between array index and index variable of outer loop is identfied.At last,the distance vector of outer loop is computed,and whether the loop has carried dependence or not is decided by examining the distance vector.The experimental results show that the proposed method can effectively recognize the dependence of branch nested loop.

Key words: Data dependence analysis,GCC,Perfect nested loop,Branch nested loops,Distance vector