How to handle missing SIMD support with a future rustup component #1289
Description
Cg_clif is missing support for a lot of SIMD intrinsics. To reduce the impact of this on user code cg_clif currently replaces the cpuid call used by is_x86_feature_detected! to return only the bare minimum supported features. This works just fine when the standard library is compiled by cg_clif, but once cg_clif gets shipped as rustup component it will have to work with a cg_llvm compiled standard library which doesn't have this workaround. As it is unrealistic to implement all those SIMD intrinsics in the immediate future, I will need to find a way to make is_x86_feature_detected! return false where necessary when using cg_clif even if the standard library is compiled with cg_llvm.