On Sun, Aug 20, 2023 at 6:44 AM ZiNgA BuRgA via Gcc-patches <gcc-patches@gcc.gnu.org> wrote: > > Hi, > > With the proposed design of these switches, how would I restrict AVX10.1 > to particular AVX-512 subsets? We can't, avx10.1 is taken as an indivisible ISA which contains all AVX512 related instructions.
> We’ve been taking these cases as bugs (but yes, intrinsics are still allowed, > so in some cases it might prove difficult to guarantee this). intel sde support avx10.1-256 target which can be used to validate the binary(if there's invalid 512-bit vector register or 64-bit kmask register is used). > I don’t see any other way of doing what you want within the constraints of > this design. It looks like the requirement is that we want a -mavx10-vector-width=256(or maybe reuse -mprefer-vector-width=256) option that acts on the original -mavx512XXX option to produce avx10.1-256 compatible binary. we can't use -mavx10.1-256 since it may include avx512fp16 directives and thus not be backward compatible SKX/CLX/ICX. > > For example, usage of the |_mm256_rol_epi32| intrinsic should be > compatible on any AVX10/256 implementation, /as well as /any AVX-512VL > without AVX10 implementation (e.g. Skylake-X). But how do I signal that > I want compatibility with both these targets? > > * |-mavx512vl| lets the compiler use 512-bit registers -> incompatible > with 256-bit AVX10. > * |-mavx512vl -mprefer-vector-width=256| might steer the compiler away > from 512-bit registers, but I don't think it guarantees it. > * |-mavx10.1-256| lets the compiler use all Sapphire Rapids AVX-512 > features at 256-bit wide (so in theory, it could choose to compile > it with |vpshldd|) -> incompatible with Skylake-X. > * |-mavx10.1-256 -mno-avx512fp16 -mno-avx512...| will emit a warning > and ignore the attempts at disabling AVX-512 subsets. > * |-mavx10.1-256 -mavx512vl| takes the /union/ of the features, not > the /intersection./ > > Is there something like |-mavx512vl -mmax-vector-width=256|, or am I > misunderstanding the situation? > > Thanks! -- BR, Hongtao
