[llvm] [BOLT] Avoid repeated hash lookups (NFC) (PR #140426)

[Kazu Hirata via llvm-commits]

kazutakahirata wrote:

> Thank you for the cleanup. We have similar helpers in `DataReader::parse` – would you mind covering them as well?

@aaupov Sure.  I've revised this PR instead of creating another one.  Please take a look.  Thanks!


https://github.com/llvm/llvm-project/pull/140426