[Mesa-dev] [PATCH] gm107/ir: use CS2R for SV_CLOCK

[Karol Herbst]

playing a bout around with nvdisasm, there seems to be some
complications with certain sched opcodes. I think we should figure out
if this is simply nvdisasm crashing or if this is a real hardware
thing.

On Tue, Jul 17, 2018 at 9:26 PM, Rhys Perry <pendingchaos02 at gmail.com> wrote:
> After some testing and looking at traces of the blob or nvcc output,
> it seems the only system value CS2R is useful for is SV_CLOCK.
>
> On Tue, Jul 17, 2018 at 1:09 PM, Karol Herbst <kherbst at redhat.com> wrote:
>> that seems like a good enough improvement. I think looking onto other
>> sysvals would be worthwhile as SV_CLOCK isn't used that often. The
>> invocation ID and related ones would be interesting to look into as
>> they are much more common.
>>
>> On Tue, Jul 17, 2018 at 1:59 PM, Rhys Perry <pendingchaos02 at gmail.com> wrote:
>>> I'm getting ~28 cycles for the S2R and ~6 cycles (unsurprisingly) for the CS2R.
>>>
>>> nvcc with SM30 seems to use the same instruction as the nvc0 emission code.
>>>
>>> The SV_LANE* system values don't work with CS2R and I haven't looked
>>> too deeply into the others.
>>>
>>> On Tue, Jul 17, 2018 at 12:13 PM, Karol Herbst <kherbst at redhat.com> wrote:
>>>> interesting, do you have some numbers on that? Wondering if we could
>>>> switch more sysvals over to it and what about older gens?
>>>>
>>>> On Tue, Jul 17, 2018 at 12:46 PM, Rhys Perry <pendingchaos02 at gmail.com> wrote:
>>>>> This instruction seems to be faster than S2R and requires no barrier,
>>>>> though the range of special registers it can read from is limited.
>>>>>
>>>>> Signed-off-by: Rhys Perry <pendingchaos02 at gmail.com>
>>>>> ---
>>>>>  src/gallium/drivers/nouveau/codegen/nv50_ir_emit_gm107.cpp | 14 +++++++++++++-
>>>>>  .../drivers/nouveau/codegen/nv50_ir_target_gm107.cpp       |  4 +++-
>>>>>  2 files changed, 16 insertions(+), 2 deletions(-)
>>>>>
>>>>> diff --git a/src/gallium/drivers/nouveau/codegen/nv50_ir_emit_gm107.cpp b/src/gallium/drivers/nouveau/codegen/nv50_ir_emit_gm107.cpp
>>>>> index 694d1b10a3..c306a4680b 100644
>>>>> --- a/src/gallium/drivers/nouveau/codegen/nv50_ir_emit_gm107.cpp
>>>>> +++ b/src/gallium/drivers/nouveau/codegen/nv50_ir_emit_gm107.cpp
>>>>> @@ -124,6 +124,7 @@ private:
>>>>>
>>>>>     void emitMOV();
>>>>>     void emitS2R();
>>>>> +   void emitCS2R();
>>>>>     void emitF2F();
>>>>>     void emitF2I();
>>>>>     void emitI2F();
>>>>> @@ -749,6 +750,14 @@ CodeEmitterGM107::emitS2R()
>>>>>     emitGPR (0x00, insn->def(0));
>>>>>  }
>>>>>
>>>>> +void
>>>>> +CodeEmitterGM107::emitCS2R()
>>>>> +{
>>>>> +   emitInsn(0x50c80000);
>>>>> +   emitSYS (0x14, insn->src(0));
>>>>> +   emitGPR (0x00, insn->def(0));
>>>>> +}
>>>>> +
>>>>>  void
>>>>>  CodeEmitterGM107::emitF2F()
>>>>>  {
>>>>> @@ -3192,7 +3201,10 @@ CodeEmitterGM107::emitInstruction(Instruction *i)
>>>>>        emitMOV();
>>>>>        break;
>>>>>     case OP_RDSV:
>>>>> -      emitS2R();
>>>>> +      if (insn->getSrc(0)->reg.data.id == SV_CLOCK)
>>>>> +         emitCS2R();
>>>>> +      else
>>>>> +         emitS2R();
>>>>>        break;
>>>>>     case OP_ABS:
>>>>>     case OP_NEG:
>>>>> diff --git a/src/gallium/drivers/nouveau/codegen/nv50_ir_target_gm107.cpp b/src/gallium/drivers/nouveau/codegen/nv50_ir_target_gm107.cpp
>>>>> index 04cbd402a1..009470fb93 100644
>>>>> --- a/src/gallium/drivers/nouveau/codegen/nv50_ir_target_gm107.cpp
>>>>> +++ b/src/gallium/drivers/nouveau/codegen/nv50_ir_target_gm107.cpp
>>>>> @@ -153,9 +153,10 @@ TargetGM107::isBarrierRequired(const Instruction *insn) const
>>>>>        case OP_AFETCH:
>>>>>        case OP_PFETCH:
>>>>>        case OP_PIXLD:
>>>>> -      case OP_RDSV:
>>>>>        case OP_SHFL:
>>>>>           return true;
>>>>> +      case OP_RDSV:
>>>>> +         return insn->getSrc(0)->reg.data.id != SV_CLOCK;
>>>>>        default:
>>>>>           break;
>>>>>        }
>>>>> @@ -229,6 +230,7 @@ TargetGM107::getLatency(const Instruction *insn) const
>>>>>     case OP_SUB:
>>>>>     case OP_VOTE:
>>>>>     case OP_XOR:
>>>>> +   case OP_RDSV:
>>>>>        if (insn->dType != TYPE_F64)
>>>>>           return 6;
>>>>>        break;
>>>>> --
>>>>> 2.14.4
>>>>>