Richard Biener <richard.guent...@gmail.com> writes: > On Thu, Nov 26, 2020 at 6:18 PM Kyrylo Tkachov via Gcc-patches > <gcc-patches@gcc.gnu.org> wrote: >> >> Hi all, >> >> This is a patch that introduces the aarch64-autovec-preference that can take >> values from 0 - 4, 0 being the default. >> It can be used to override the autovectorisation preferences in the backend: >> 0 - use default scheme >> 1 - only use Advanced SIMD >> 2 - only use SVE >> 3 - use Advanced SIMD and SVE, prefer Advanced SIMD in the event of a tie >> (as determined by costs) >> 4 - use Advanced SIMD and SVE, prefer SVE in the event of a tie (as >> determined by costs) >> >> It can valuable for experimentation when comparing SVE and Advanced SIMD >> autovectorisation strategies. >> >> It achieves this adjusting the order of the interleaved SVE and Advanced >> SIMD modes in aarch64_autovectorize_vector_modes. >> It also adjusts aarch64_preferred_simd_mode to use the new comparison >> function to pick Advanced SIMD or SVE to start with. >> >> Bootstrapped and tested on aarch64-none-linux-gnu. >> Ok for master (since it touches much SVE-related code by Richard I'd feel >> more comfortable with a second pair of eyes)?
LGTM. > Is this supposed to be used internally or for development purposes? > If users are supposed > to use this then a -m switch would be more appropriate (x86 for example has > -mprefer-vector-width) I think it's more production vs. experimentation rather than developer vs. user. Users shouldn't have to worry about this kind of thing when they're doing production builds: specifying -mcpu or -mtune should be enough to get the right behaviour. But having a --param like this that we can point users at is useful for getting feedback or as an interim workaround until an optimisation bug is fixed. And like you say, it's also useful for running experiments for development. Thanks, Richard
