[Mesa-dev] [PATCH 2/3] nv50/ir: optimize slct(b, c, set(a, 0)) to slct(b, c, a)

[Ilia Mirkin]

On Fri, Dec 14, 2018 at 6:12 PM Karol Herbst <kherbst at redhat.com> wrote:
>
> From: Karol Herbst <karolherbst at gmail.com>
>
> helps mainly feral ported games
>
> shader-db changes:
> total instructions in shared programs     : 7614782 -> 7565661 (-0.65%)
> total gprs used in shared programs        : 798045 -> 797213 (-0.10%)
> total shared used in shared programs      : 639636 -> 639636 (0.00%)
> total local used in shared programs       : 24648 -> 24648 (0.00%)
> total bytes used in shared programs       : 81330696 -> 80806160 (-0.64%)
>
>                 local     shared        gpr       inst      bytes
>     helped          0          0        701       7940       7940
>       hurt          0          0         44          4          4
>
> Signed-off-by: Karol Herbst <kherbst at redhat.com>
> ---
>  .../nouveau/codegen/nv50_ir_peephole.cpp      | 47 +++++++++++++++++--
>  1 file changed, 44 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 a8bd4f868bf..37e9edc49f4 100644
> --- a/src/gallium/drivers/nouveau/codegen/nv50_ir_peephole.cpp
> +++ b/src/gallium/drivers/nouveau/codegen/nv50_ir_peephole.cpp
> @@ -1763,7 +1763,8 @@ private:
>     bool tryADDToMADOrSAD(Instruction *, operation toOp);
>     void handleMINMAX(Instruction *);
>     void handleRCP(Instruction *);
> -   void handleSLCT(Instruction *);
> +   void handleSLCT(CmpInstruction *);
> +   bool tryMergeSLCTSET(CmpInstruction *slct, CmpInstruction *set);

SLCT_SET or SET_SLCT. Otherwise it all runs together.

>     void handleLOGOP(Instruction *);
>     void handleCVT_NEG(Instruction *);
>     void handleCVT_CVT(Instruction *);
> @@ -1956,8 +1957,12 @@ AlgebraicOpt::handleRCP(Instruction *rcp)
>  }
>
>  void
> -AlgebraicOpt::handleSLCT(Instruction *slct)
> +AlgebraicOpt::handleSLCT(CmpInstruction *slct)
>  {
> +   Instruction *insn = slct->getSrc(2)->getInsn();
> +   while(insn && insn->op == OP_SET && tryMergeSLCTSET(slct, insn->asCmp())) {

while (

> +      insn = slct->getSrc(2)->getInsn();
> +   }
>     if (slct->getSrc(2)->reg.file == FILE_IMMEDIATE) {
>        if (slct->getSrc(2)->asImm()->compare(slct->asCmp()->setCond, 0.0f))
>           slct->setSrc(0, slct->getSrc(1));
> @@ -1970,6 +1975,42 @@ AlgebraicOpt::handleSLCT(Instruction *slct)
>     slct->setSrc(2, NULL);
>  }
>
> +bool
> +AlgebraicOpt::tryMergeSLCTSET(CmpInstruction *slct, CmpInstruction *set)
> +{
> +   assert(slct->op == OP_SLCT && set->op == OP_SET);
> +
> +   if (typeSizeof(set->sType) != 4)
> +      return false;
> +
> +   CondCode setCC = set->getCondition();
> +   CondCode slctCC = slct->getCondition();
> +   CondCode newCC = setCC;
> +
> +   if (slctCC != CC_NE && slctCC != CC_EQ)
> +      return false;
> +
> +   ImmediateValue imm0;
> +   int s;
> +
> +   if (set->src(0).getImmediate(imm0) && imm0.isInteger(0))
> +      s = 1;
> +   else if (set->src(1).getImmediate(imm0) && imm0.isInteger(0))
> +      s = 0;
> +   else
> +      return false;
> +
> +   slct->setSrc(2, set->getSrc(s));
> +   if (s)
> +      newCC = reverseCondCode(newCC);
> +   if (slctCC == CC_EQ)
> +      newCC = inverseCondCode(newCC);

While not wrong, this is all pretty confusing. I won't require it, but
I'd like to encourage you to write a paragraph about the theory about
wtf is going on here.

> +
> +   slct->sType = set->sType;
> +   slct->setCondition(newCC);
> +   return true;
> +}
> +
>  void
>  AlgebraicOpt::handleLOGOP(Instruction *logop)
>  {
> @@ -2340,7 +2381,7 @@ AlgebraicOpt::visit(BasicBlock *bb)
>           handleMINMAX(i);
>           break;
>        case OP_SLCT:
> -         handleSLCT(i);
> +         handleSLCT(i->asCmp());
>           break;
>        case OP_AND:
>        case OP_OR:
> --
> 2.19.2
>