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

[Madhur Amilkanthwar via llvm-commits]

madhur13490 wrote:

> Missing justification for the change. This looks very wrong to me, as partial profiles are common. The optimization for the non-profiled parts should be the same as absence of the profile.

Some of the internal workloads have GVN in the top 5 when profiled for compile-time. Is there a way to disambiguate from a partial profile?

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