Richard Biener <rguent...@suse.de> writes: > On Tue, 26 May 2020, Jim Wilson wrote: > >> On Tue, May 26, 2020 at 12:12 AM Richard Biener <rguent...@suse.de> wrote: >> > From a look at the series description below you seem to add a new way >> > of doing loads for this. Did you review other ISAs (those I'm not >> > familiar with myself too much are SVE, RISC-V and GCN) in GCC whether >> > they have similar support and whether your approach can be supported >> > there? ISTR SVE must have some similar support - what's the reason >> > you do not piggy-back on that? >> >> There isn't any RISC-V Vector support in GCC yet. The RVV spec is >> still in draft and still occasionally changing in incompatible ways. >> We've done some experimenting with gcc patches, but all we have are >> intrinsics. We haven't implemented any auto vectorization support, so >> we haven't defined tree representations for anything yet, other than >> the types we need for intrinsics support. But if it looks OK for SVE >> then it probably will be OK for RVV. > > Btw, I'm specifically looking for other load/store with length > implementations and as to whether they agree on taking bytes for > the length rather than, for example the number of lanes. I guess > exposing this detail on GIMPLE can help IV selection but if we'd > ever get a differing semantics ISA we'd have to add another set > of IFNs, so maybe the PPC ones should be named in a more specific > way like _WITH_BYTES or _BYTES or _WITH_BYTE_LENGTH or so to > allow _WITH_LANES?
Maybe that detail is another thing that a cookie could hide. We'd then potentially need one IFN per approach to calculating the length parameter (bytes vs. elements, self-capping vs. explicit capping, etc.), but it would only be one IFN per approach, rather than the combinatorial explosion we'd get from one IFN per approach*load/store-kind. It doesn't make much difference when we only have one LOAD and one STORE per approach. But I imagine this will be useful for MVE, and there we'll want extending loads, truncating stores, gathers and scatters too. Thanks, Richard
