[llvm] [SelectionDAG] Allow lowering CTPOP into a libcall (PR #99752)

[Sergei Barannikov via llvm-commits]

s-barannikov wrote:

> > but I don't know if the libcall is available in their libgcc
> 
> Should be easy to find out?

Right. It appears it is available and gcc uses it for `__builtin_popcount[l,ll]` even when optimizing for speed (-Ofast).
There is no 128-bit version though.
I'll update the PR.


https://github.com/llvm/llvm-project/pull/99752