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

Francisco Jerez currojerez at riseup.net
Thu Feb 19 12:13:00 PST 2015

Jason Ekstrand <jason at jlekstrand.net> writes:

> 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.

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

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