[llvm] [llvm-exegesis] Use hex values when parsing memory mappings (PR #72620)

[Aiden Grossman via llvm-commits]

boomanaiden154 wrote:

@ondrasej 

There are relatively few (known) users of the memory annotations in `llvm-exegesis`, so I don't believe this change should have any significant impact on existing users and will probably make it easier to use for those existing users (have had at least one question about that so far).

https://github.com/llvm/llvm-project/pull/72620