[llvm] Enable logf128 constant folding for hosts with 128bit long double (PR #104929)

[Amy Kwan via llvm-commits]

amy-kwan wrote:

I would also be ok with a revert of this patch for now. Would that be possible?
It's still causing issues on three of the PPC buildbots:
https://lab.llvm.org/buildbot/#/builders/95/builds/2838
https://lab.llvm.org/buildbot/#/builders/76/builds/2182
https://lab.llvm.org/buildbot/#/builders/168/builds/2502

https://github.com/llvm/llvm-project/pull/104929