[llvm] [IntrinsicLowering] Allow implicit truncation of ctpop masks (PR #229373)

[Aochang Liu via llvm-commits]

HelloWorldU wrote:

> Note that the interpreter, which is the only place where this is used, will be removed (https://discourse.llvm.org/t/rfc-delete-executionengine-interpreter/91720).
> 
> I'm willing to merge this given that the fix is trivial, but generally I'm not willing to accept fixes to the interpreter anymore.

I see. If moved to Interpreter/, the test would only run with `LLVM_ENABLE_FFI`, which is not in premerge CI. Or I could just close this PR since the interpreter is going away.

https://github.com/llvm/llvm-project/pull/229373