[clang] [clang] Implement __builtin_popcountg (PR #82359)

[Eli Friedman via cfe-commits]

efriedma-quic wrote:

Oh, I should have caught that when reviewing.  (I thought I checked the test was doing the right thing when I looked at it, but I guess I'm misremembering.)

Probably need to mark the intrinsic CustomTypeChecking, then make the code in SemaChecking explicitly perform lvalue-to-rvalue conversions, to match gcc.

Yes, please open an issue... or if you're planning to look at it, feel free to just post a fix.

https://github.com/llvm/llvm-project/pull/82359