On Wed, Mar 22, 2023 at 12:02 PM Andrew Stubbs <a...@codesourcery.com> wrote: > > On 22/03/2023 10:09, Richard Biener wrote: > > On Tue, Mar 21, 2023 at 6:00 PM Andrew Stubbs <a...@codesourcery.com> wrote: > >> > >> Hi all, > >> > >> I want to be able to vectorize divide operators (softfp and integer), > >> but amdgcn only has hardware instructions suitable for -ffast-math. > >> > >> We have recently implemented vector versions of all the libm functions, > >> but the libgcc functions aren't builtins and therefore don't use those > >> hooks. > >> > >> What's the best way to achieve this? Add a new __builtin_div (and > >> __builtin_mod) that tree-vectorize can find, perhaps? Or something else? > > > > What do you want to do? Vectorize the out-of-line libgcc copy? Or > > emit inline vectorized code for int/softfp operations? In the latter > > case just emit the code from the pattern expanders? > > I'd like to investigate having vectorized versions of the libgcc > instruction functions, like we do for libm. > > The inline code expansion is certainly an option, but I think there's > quite a lot of code in those routines. I know how to do that option at > least (except, maybe not the errno handling without making assumptions > about the C runtime). > > Basically, the -ffast-math instructions will always be the fastest way, > but the goal is that the default optimization shouldn't just disable > vectorization entirely for any loop that has a divide in it.
We try to express division as multiplication, but yes, I think there's currently no way to tell the vectorizer that vectorized division is available as libcall (nor for any other arithmetic operator that is not a call in the first place). > Andrew
