[Mesa-dev] [PATCH 3/4] nvc0/ir: Handle OP_POPCNT when folding constant expressions

[Ilia Mirkin]

On Thu, May 29, 2014 at 3:43 PM, Tobias Klausmann
<tobias.johannes.klausmann at mni.thm.de> wrote:
> Signed-off-by: Tobias Klausmann <tobias.johannes.klausmann at mni.thm.de>
> ---
>  src/gallium/drivers/nouveau/codegen/nv50_ir_peephole.cpp | 10 ++++++++++
>  1 file changed, 10 insertions(+)
>
> diff --git a/src/gallium/drivers/nouveau/codegen/nv50_ir_peephole.cpp b/src/gallium/drivers/nouveau/codegen/nv50_ir_peephole.cpp
> index 93f7c2a..68b9a6d 100644
> --- a/src/gallium/drivers/nouveau/codegen/nv50_ir_peephole.cpp
> +++ b/src/gallium/drivers/nouveau/codegen/nv50_ir_peephole.cpp
> @@ -546,6 +546,16 @@ ConstantFolding::expr(Instruction *i,
>        }
>        break;
>     }
> +   case OP_POPCNT: {
> +      switch (i->dType) {
> +      case TYPE_S32:
> +      case TYPE_U32:
> +         res.data.u32 = util_bitcount(a->data.u32 & b->data.u32); break;
> +      default:
> +        return;
> +      }
> +      break;
> +   }

Why does the data type matter? I think you can handle this like AND is
handled -- just always do it.

Also, please add support for a single-argument version of POPCNT. This
will happen as a result of lowering for sm50 (maxwell), for which it's
a 1-arg instruction. Basically you need to add a case to opnd() which
checks that there's only one argument and does it accordingly. [The
existing function assumes a float op, and it'd be a pain to modify
it.]

>     default:
>        return;
>     }
> --
> 1.8.4.5
>