[llvm] [GVN][PGO] Skip GVN if entry BlockFreq is 0 (PR #166336)

[via llvm-commits]

rightrotate wrote:

Hi,
My company, RRL, is a downstream user of PGO. We find this patch useful as it allows us to skip the pass. GVN has been painful several times, and skipping it on "dead" code is useful.

> I don't think this change makes sense, even on a temporary basis

I disagree. This does make sense. What is the problem of having this and keeping it under a flag? There are numerous other flags that can help.

https://github.com/llvm/llvm-project/pull/166336