How to improve the speed of afl-cov's calculation of coverage?

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Currently, afl-cov needs the output file of afl-fuzz to calculate coverage, which means that two processes are required. But if there are multiple files and the target program is very large, the calculation speed will be very slow. Does afl-cov support reading the bitmap to calculate the coverage, which will speed up the calculation?

Or, to think about this more simply, afl-cov now generates the coverage of each file. Which option allows me to get the overall coverage without so many details?