[clang] [clang] Fix sub-integer __builtin_elementwise_(add|sub)_sat (PR #119423)

[Fraser Cormack via cfe-commits]

frasercrmck wrote:

> I thought bitreverse/popcount are only supposed to work with unsigned types?

Good question. The [documentation](https://clang.llvm.org/docs/LanguageExtensions.html) doesn't mention they're only for signed types, as `abs` does, for example. So if there is such a restriction, it's not documented, nor checked in the code.

Tangentially, in OpenCL (where I'm coming from) there's no restriction on `popcount` to be only on unsigned types.

https://github.com/llvm/llvm-project/pull/119423