[Mesa-dev] [PATCH] nv50/ir: Add mul and mod constant optimizations

[Ilia Mirkin]

You handle 1/n but not 1%n? TBH, the 1/n code isn't 100% obvious to
me... 1/n = |n|-1 > 0 ? .... i forget how SLCT works, but I can't
think of a way to finish that expression in terms of |n|-1 and n. And
what about n == 0. I'd just as soon drop that case.

On Tue, Jul 23, 2019 at 10:20 AM Mark Menzynski <mmenzyns at redhat.com> wrote:
>
> Optimizations for 0/n, 1/n and 0%n.
> No changes in shader db tests, because it is never used here, but it
> should become handy.
>
> Signed-off-by: Mark Menzynski <mmenzyns at redhat.com>
> ---
>  .../nouveau/codegen/nv50_ir_peephole.cpp      | 30 +++++++++++++++++--
>  1 file changed, 28 insertions(+), 2 deletions(-)
>
> diff --git a/src/gallium/drivers/nouveau/codegen/nv50_ir_peephole.cpp b/src/gallium/drivers/nouveau/codegen/nv50_ir_peephole.cpp
> index 0b3220903b9..12069e19808 100644
> --- a/src/gallium/drivers/nouveau/codegen/nv50_ir_peephole.cpp
> +++ b/src/gallium/drivers/nouveau/codegen/nv50_ir_peephole.cpp
> @@ -1177,10 +1177,28 @@ ConstantFolding::opnd(Instruction *i, ImmediateValue &imm0, int s)
>        break;
>
>     case OP_DIV:
> -      if (s != 1 || (i->dType != TYPE_S32 && i->dType != TYPE_U32))
> +      if (i->dType != TYPE_S32 && i->dType != TYPE_U32)
>           break;
> +
>        bld.setPosition(i, false);
> -      if (imm0.reg.data.u32 == 0) {
> +      if (s == 0) {
> +         if (imm0.reg.data.u32 == 0) {
> +            i->op = OP_MOV;
> +            i->setSrc(1, NULL);
> +         }
> +         else if (imm0.reg.data.u32 == 1) {
> +            Value *tA, *tB;
> +            Instruction *slct;
> +
> +            tA = bld.mkOp1v(OP_ABS, TYPE_U32, bld.getSSA(), i->getSrc(1));
> +            tB = bld.mkOp2v(OP_ADD, TYPE_S32, bld.getSSA(), tA, bld.loadImm(NULL, -1));
> +            slct = bld.mkCmp(OP_SLCT, CC_GT, i->dType, bld.getSSA(), TYPE_U32, bld.loadImm(NULL, 0), i->getSrc(1), tB);
> +            i->def(0).replace(slct->getDef(0), false);
> +         }
> +         break;
> +      }
> +
> +      if (s != 1 || imm0.reg.data.u32 == 0) {
>           break;
>        } else
>        if (imm0.reg.data.u32 == 1) {
> @@ -1259,6 +1277,14 @@ ConstantFolding::opnd(Instruction *i, ImmediateValue &imm0, int s)
>        break;
>
>     case OP_MOD:
> +      if (s == 0) {
> +         if (imm0.reg.data.u32 == 0) {
> +            i->op = OP_MOV;
> +            i->setSrc(1, NULL);
> +         }
> +         break;
> +      }
> +
>        if (s == 1 && imm0.isPow2()) {
>           bld.setPosition(i, false);
>           if (i->sType == TYPE_U32) {
> --
> 2.21.0
>
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