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

[Rhys Perry]

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
>>