[Mesa-dev] [PATCH 11/14] i965/compaction: Add support for G45.

[Jason Ekstrand]

On Tue, Sep 23, 2014 at 1:28 PM, Matt Turner <mattst88 at gmail.com> wrote:

> On Tue, Sep 23, 2014 at 1:19 PM, Jason Ekstrand <jason at jlekstrand.net>
> wrote:
> > On Thu, Aug 28, 2014 at 8:10 PM, Matt Turner <mattst88 at gmail.com> wrote:
> >>     int offset = 0;
> >> @@ -1319,17 +1323,22 @@ brw_compact_instructions(struct brw_compile *p,
> >> int start_offset,
> >>           offset += sizeof(brw_compact_inst);
> >>        } else {
> >>           /* It appears that the end of thread SEND instruction needs to
> >> be
> >> -          * aligned, or the GPU hangs.
> >> +          * aligned, or the GPU hangs. All uncompacted instructions
> need
> >> to be
> >> +          * aligned on G45.
> >>            */
> >> -         if ((brw_inst_opcode(brw, src) == BRW_OPCODE_SEND ||
> >> -              brw_inst_opcode(brw, src) == BRW_OPCODE_SENDC) &&
> >> -             brw_inst_eot(brw, src) &&
> >> -             (offset & sizeof(brw_compact_inst)) != 0) {
> >> +         if ((offset & sizeof(brw_compact_inst)) != 0 &&
> >> +             (((brw_inst_opcode(brw, src) == BRW_OPCODE_SEND ||
> >> +                brw_inst_opcode(brw, src) == BRW_OPCODE_SENDC) &&
> >> +               brw_inst_eot(brw, src)) ||
> >> +              brw->is_g4x)) {
> >>              brw_compact_inst *align = store + offset;
> >>              memset(align, 0, sizeof(*align));
> >> -            brw_compact_inst_set_opcode(align, BRW_OPCODE_NOP);
> >> +            brw_compact_inst_set_opcode(align, brw->is_g4x ?
> >> BRW_OPCODE_NENOP :
> >> +
> >> BRW_OPCODE_NOP);
> >>              brw_compact_inst_set_cmpt_control(align, true);
> >>              offset += sizeof(brw_compact_inst);
> >> +            compacted_count--;
> >> +            compacted_counts[src_offset / sizeof(brw_inst)] =
> >> compacted_count;
> >
> >
> > Do these two lines really belong in this patch?  They seem completely
> > unrelated to stuff on G45.
>
> Yes, because if you have to insert a padding NENOP, you need to update
> the compaction_count (which is really a metric of how far offset you
> are because of the space saved by compacted instructions).
>
> So, really what it's doing is not considering compacted instructions
> as saving space if we had to insert a padding NENOP after it.
>

Why didn't we need that post-gen5 and, if we didn't, why are we doing it
unconditionally?
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