[Nouveau] [PATCH] nv50/ir: Propagate third immediate src when folding OP_MAD

[Ilia Mirkin]

That's very odd. LoadPropagation should have picked that up even in
its current form. Should try to figure out why it didn't and that is
likely to "fix" a *lot* more situations.

On Sun, Oct 2, 2016 at 2:24 PM, Tobias Klausmann
<tobias.johannes.klausmann at mni.thm.de> wrote:
>
>
> On 02.10.2016 20:03, Ilia Mirkin wrote:
>>
>> On Sun, Oct 2, 2016 at 1:58 PM, Tobias Klausmann
>> <tobias.johannes.klausmann at mni.thm.de> wrote:
>>>
>>> Previously we'd end up with an unnecessary mov for the thirs immediate
>>> value.
>>>
>>> total instructions in shared programs : 851881 -> 851864 (-0.00%)
>>> total gprs used in shared programs    : 110295 -> 110295 (0.00%)
>>> total local used in shared programs   : 1020 -> 1020 (0.00%)
>>>
>>>                  local        gpr       inst      bytes
>>>      helped           0           0          17          17
>>>        hurt           0           0           0           0
>>>
>>> Suggested-by: Karol Herbst <nouveau at karolherbst.de>
>>> Signed-off-by: Tobias Klausmann <tobias.johannes.klausmann at mni.thm.de>
>>> ---
>>>   src/gallium/drivers/nouveau/codegen/nv50_ir_peephole.cpp | 15
>>> ++++++++++++---
>>>   1 file changed, 12 insertions(+), 3 deletions(-)
>>>
>>> diff --git a/src/gallium/drivers/nouveau/codegen/nv50_ir_peephole.cpp
>>> b/src/gallium/drivers/nouveau/codegen/nv50_ir_peephole.cpp
>>> index 9875738..8bb5cf9 100644
>>> --- a/src/gallium/drivers/nouveau/codegen/nv50_ir_peephole.cpp
>>> +++ b/src/gallium/drivers/nouveau/codegen/nv50_ir_peephole.cpp
>>> @@ -1008,13 +1008,22 @@ ConstantFolding::opnd(Instruction *i,
>>> ImmediateValue &imm0, int s)
>>>         break;
>>>      case OP_MAD:
>>>         if (imm0.isInteger(0)) {
>>> +         ImmediateValue imm1;
>>>            i->setSrc(0, i->getSrc(2));
>>>            i->src(0).mod = i->src(2).mod;
>>>            i->setSrc(1, NULL);
>>>            i->setSrc(2, NULL);
>>> -         i->op = i->src(0).mod.getOp();
>>> -         if (i->op != OP_CVT)
>>> -            i->src(0).mod = 0;
>>> +         if (i->src(0).getImmediate(imm1)) {
>>> +            bld.setPosition(i, false);
>>> +            newi = bld.mkMov(i->getDef(0), bld.mkImm(imm1.reg.data.u64),
>>> +                             i->dType);
>>> +            delete_Instruction(prog, i);
>>
>> What's an example of a situation where this helps? It shouldn't
>> matter, the mov's should get cleaned up. [Clearly 17 shaders
>> disagree...] Is this just a side-effect of the fact that we don't run
>> the opts to a fixed point?
>
>
> It is a second mov that causes a problem for later folding in the imm, here
> output of a testshader[1]:
>
>   0: nop u32 %r56 (0)
>   1: ld  u32 %r31 c0[0x0] (0)
>   2: ld  u32 %r37 c0[0x140] (0)
>   3: mov u32 %r38 0x00000000 (0)
>   4: mov u32 %r39 0x3f800000 (0)
>   5: mad f32 %r40 %r37 %r38 %r39 (0)
>   6: mad f32 %r44 %r37 %r38 %r38 (0)
>   7: add f32 %r53 %r31 %r40 (0)
>   8: add f32 %r54 %r31 %r44 (0)
>   9: add f32 %r57 %r56 %r44 (0)
>
> Constantfolding...
>
> MAIN:-1 ()
> BB:0 (14 instructions) - df = { }
>  -> BB:1 (tree)
>   0: nop u32 %r56 (0)
>   1: ld  u32 %r31 c0[0x0] (0)
>   2: ld  u32 %r37 c0[0x140] (0)
>   3: mov u32 %r38 0x00000000 (0)
>   4: mov u32 %r39 0x3f800000 (0)
>   5: mov f32 %r40 %r39 (0)
>   6: mov f32 %r44 %r38 (0)
>   7: add f32 %r53 %r31 %r40 (0)
>   8: mov f32 %r54 %r31 (0)
>   9: mov f32 %r57 %r56 (0)
>
>
> The outcome:
>   0: ld  u32 $r2 c0[0x0] (8)
>   1: mov u32 $r0 0x3f800000 (8)
>   2: add ftz f32 $r0 $r2 $r0 (8)
>   3: mov f32 $r3 $r1 (8)
>   4: mov u32 $r1 $r2 (8)
>   5: export b128 # o[0x0] $r0q (8)
>
> With patch:
>   0: ld  u32 $r2 c0[0x0] (8)
>   1: add ftz f32 $r0 $r2 1.000000 (8)
>   2: mov f32 $r3 $r1 (8)
>   3: mov u32 $r1 $r2 (8)
>   4: export b128 # o[0x0] $r0q (8)
>
>
> [1]:
> VERT
> PROPERTY NEXT_SHADER FRAG
> DCL OUT[0], GENERIC[0]
> DCL CONST[0]
> DCL TEMP[0..1], LOCAL
> IMM[0] FLT32 {    0.0078,    -1.0000,     0.0000,     0.5000}
> IMM[1] FLT32 {    1.0000,     0.0000, 65535.0000,     0.0100}
>   0: MOV TEMP[0].xyz, CONST[0].xxxx
>  39: MAD TEMP[1], CONST[20].xxxx, IMM[1].yyyy, IMM[1].xyyy
>  41: ADD TEMP[1], TEMP[0], TEMP[1]
> 208: MOV OUT[0], TEMP[1]
> 211: END
>
>
>
>
>>
>>> +         }
>>> +         else {
>>> +            i->op = i->src(0).mod.getOp();
>>> +            if (i->op != OP_CVT)
>>> +               i->src(0).mod = 0;
>>> +         }
>>>         } else
>>>         if (i->subOp != NV50_IR_SUBOP_MUL_HIGH &&
>>>             (imm0.isInteger(1) || imm0.isInteger(-1))) {
>>> --
>>> 2.10.0
>>>
>>> _______________________________________________
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>>> Nouveau at lists.freedesktop.org
>>> https://lists.freedesktop.org/mailman/listinfo/nouveau
>
>