D43208 extracted useEmulatedMaskMemRefHack() from legality into cost model.
What it essentially does is prevents scalarized vectorization of masked memory operations:
// TODO: Cost model for emulated masked load/store is completely // broken. This hack guides the cost model to use an artificially // high enough value to practically disable vectorization with such // operations, except where previously deployed legality hack allowed // using very low cost values. This is to avoid regressions coming simply // from moving "masked load/store" check from legality to cost model. // Masked Load/Gather emulation was previously never allowed. // Limited number of Masked Store/Scatter emulation was allowed.
While i don't really understand about what specifically is completely broken
was talking about, i believe that at least on X86 with AVX2-or-later,
this is no longer true. (or at least, i would like to know what is still broken).
So i would like to follow suit after D111460, and like wise disable that hack for AVX2+.
But since this was added for X86 specifically, let's just instead completely remove this hack.