On Thu, Feb 19, 2015 at 1:25 PM, Francisco Jerez <curroje...@riseup.net> wrote:
> Jason Ekstrand <ja...@jlekstrand.net> writes: > > > On Thu, Feb 19, 2015 at 12:13 PM, Francisco Jerez <curroje...@riseup.net > > > > wrote: > > > >> Jason Ekstrand <ja...@jlekstrand.net> writes: > >> > >> > On Fri, Feb 6, 2015 at 4:01 PM, Francisco Jerez < > curroje...@riseup.net> > >> > wrote: > >> > > >> >> Hey Matt, > >> >> > >> >> Matt Turner <matts...@gmail.com> writes: > >> >> > >> >> > On Fri, Feb 6, 2015 at 6:42 AM, Francisco Jerez < > >> curroje...@riseup.net> > >> >> wrote: > >> >> >> MRFs cannot be read from anyway so they cannot possibly be a valid > >> >> >> source of LOAD_PAYLOAD. > >> >> >> --- > >> >> > > >> >> > The function only seems to test inst->dst.file == MRF. I don't see > any > >> >> > code for handling MRF sources. What am I missing? > >> >> > >> >> That test is for "handling" MRF sources -- More precisely, it's > >> >> collecting the writemask and half flags for MRF writes, which can > only > >> >> possibly be useful if we're going to use them later on to read > something > >> >> out of an MRF into a payload, which we shouldn't be doing in the > first > >> >> place. > >> >> > >> >> Aside from simplifying the function somewhat, that allows us to drop > the > >> >> 16 register gap reserved for MRFs at register offset zero, what will > >> >> allow us to drop the vgrf_to_reg[] offset calculation completely > (also > >> >> in split_virtual_grfs()) in a future patch (not sent for review yet). > >> >> > >> > > >> > No, we do read from MRF's sort-of... Send messages have an implicit > >> "read" > >> > from an MRF. > >> > >> Heh, and that's pretty much the only way you "read" from it. > >> > >> > This was written precicely so that we could use LOAD_PAYLOAD > >> > to build MRF payloads. We do on pre-GEN6. > >> > > >> I'm aware, but you don't need any of this meta-data to LOAD_PAYLOAD > >> *into* an MRF, and LOAD_PAYLOAD with an MRF as source should be illegal > >> anyway. > >> > > > > And no one is using it that way. All of the metadata checks you are > > deleting are checks on the *destination*. > > > > Didn't you write this code yourself? The only use for the collected > metadata is initializing the instruction flags of the MOVs subsequent > LOAD_PAYLOAD instructions are lowered to, based on the metadata already > collected for its source registers, which can never be MRFs, so the > metadata you collect from MRF writes is never actually used. > Right... I misred something initially. Yes, we should never be tracking MRF's as a source of a LOAD_PAYLOAD. I'll give it a better look a bit later, but it looks better.
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