[Mesa-dev] [PATCH 10/32] i965/fs: Remove logic to keep track of MRF metadata in lower_load_payload().

Jason Ekstrand jason at jlekstrand.net
Thu Feb 19 11:35:04 PST 2015


On Fri, Feb 6, 2015 at 4:01 PM, Francisco Jerez <currojerez at riseup.net>
wrote:

> Hey Matt,
>
> Matt Turner <mattst88 at gmail.com> writes:
>
> > On Fri, Feb 6, 2015 at 6:42 AM, Francisco Jerez <currojerez at 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.  This was written precicely so that we could use LOAD_PAYLOAD
to build MRF payloads.  We do on pre-GEN6.


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