Compilation flags for AWS CPUs

I'm using AWS and would like to optimize some apps running on ARM architecture -I'm referring to instances a1 & m6g (and future c6g) instances-. I was able to dig some technical specs about the CPUs but was wondering if anyone is familiar with the GNU compilation flags to optimize performance. More specifically, and looking at, does anyone have any suggestion on which values to use for the flags -march, -mtune, and -mcpu? For example, for an a1 instance, the -march flag is probably going to be armv8 but there are like 11 different options. Thanks.

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