[Mesa-dev] [PATCH 1/2] nir: add a helper function for getting the number of source components

[Jason Ekstrand]

On Sun, Jan 25, 2015 at 8:56 AM, Connor Abbott <cwabbott0 at gmail.com> wrote:

> Unlike with non-SSA ALU instructions, where if they're per-component
> you have to look at the writemask to know which source channels are
> being used, SSA ALU instructions always have all the possible channels
> enabled so we can just look at the number of components in the SSA
> definition for per-component instructions to say how many source
> components are being used.
>
> Signed-off-by: Connor Abbott <cwabbott0 at gmail.com>
> ---
>  src/glsl/nir/nir.h | 15 +++++++++++++++
>  1 file changed, 15 insertions(+)
>
> diff --git a/src/glsl/nir/nir.h b/src/glsl/nir/nir.h
> index 0ef83a1..efcaa9d 100644
> --- a/src/glsl/nir/nir.h
> +++ b/src/glsl/nir/nir.h
> @@ -652,6 +652,21 @@ nir_alu_instr_channel_used(nir_alu_instr *instr,
> unsigned src, unsigned channel)
>     return (instr->dest.write_mask >> channel) & 1;
>  }
>
> +/*
> + * For instructions whose destinations are SSA, get the number of channels
> + * used for a source
> + */
> +static inline unsigned
> +nir_alu_instr_ssa_src_components(nir_alu_instr *instr, unsigned src)
>

The name instr_ssa_src_components is kind of deceiving when the source
isn't what has to be SSA.  It's the destination that's SSA.  I'm not coming
up with a better name off hand, but we should try and find one.

Also, There are a lot of other places that need this than just constant
folding.  A quick grep for input_sizes would probably reveal the ones that
are open-coding it.  Other than that, I like the series.
--Jason


> +{
> +   assert(instr->dest.dest.is_ssa);
> +
> +   if (nir_op_infos[instr->op].input_sizes[src] > 0)
> +      return nir_op_infos[instr->op].input_sizes[src];
> +
> +   return instr->dest.dest.ssa.num_components;
> +}
> +
>  typedef enum {
>     nir_deref_type_var,
>     nir_deref_type_array,
> --
> 2.1.0
>
>
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