[llvm] ConstantFold logl calls (PR #94944)

[Matthew Devereau via llvm-commits]

MDevereau wrote:

> > Done, I've removed the zero and negative checks as well to keep it consistent with the logf.128 behaviour.
> 
> It needs to produce the same errno and fpexeption values. I can see that the intrinsic remains, but would recommend making it work the same as floats: https://godbolt.org/z/T5x7foe4Y

I think I've done what you asked for. I'm a bit unsure about the infinity test case though.

https://github.com/llvm/llvm-project/pull/94944