[llvm] [llvm-profdata] Reject merging single-byte-coverage with count profiles (PR #213177)

[via llvm-commits]

gulfemsavrun wrote:

> Or maybe it makes more sense to "downgrade" the indexed profile to single-byte coverage if we merge any indexed profile with single-byte coverage.

That makes a lot of sense to me.

https://github.com/llvm/llvm-project/pull/213177