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

[Nikita Popov via llvm-commits]

nikic wrote:

The problem is that this is papering over the issue in a way that might benefit some specific users, but still leaves it for everyone else (especially as this is behind a flag). *Everyone* will be better off if the problematic case can be addressed directly.

Is it possible to share any test cases that exhibit the compile time issue this PR is trying to address?

At this point it's mainly not clear to me that it's really impossible (with reasonable effort) to fix this in a way that does not rely on PGO plus an internal option.

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