[FFmpeg-devel] [PATCH 4/5] lavu/intmath.h: Fix UB in ff_ctz_c() and ff_ctzll_c()

[Rémi Denis-Courmont]

Le 30 mai 2024 17:03:09 GMT+03:00, "Tomas Härdin" <git at haerdin.se> a écrit :
>> I don't get how that prevents using the GCC and Clang builtins (on
>> GCC and Clang).
>
>Does MSVC have builtins for these?

I don't know, but insofar as MSVC is used for x86, it should use x86 instructions rather than the complex fallback algo anyway, be it via built-ins, or assembler.

Either way, I don't see how that detracts from using the built-ins on compilers that do have them.

> Do all compilers we support?

No, unless all other compilers are C23 (CTZ and CLZ are in stdbit.h). Again, that's hardly a reason not to use built-ins where available.