[Mesa-dev] [PATCH 06/13] nir/lower_double_ops: lower floor()

[Jason Ekstrand]

On Tue, Apr 12, 2016 at 1:05 AM, Samuel Iglesias Gonsálvez <
siglesias at igalia.com> wrote:

> From: Iago Toral Quiroga <itoral at igalia.com>
>
> At least i965 hardware does not have native support for floor on doubles.
> ---
>  src/compiler/nir/nir.h                  |  1 +
>  src/compiler/nir/nir_lower_double_ops.c | 29 +++++++++++++++++++++++++++++
>  2 files changed, 30 insertions(+)
>
> diff --git a/src/compiler/nir/nir.h b/src/compiler/nir/nir.h
> index f83b2e0..b7231a7 100644
> --- a/src/compiler/nir/nir.h
> +++ b/src/compiler/nir/nir.h
> @@ -2287,6 +2287,7 @@ typedef enum {
>     nir_lower_dsqrt = (1 << 1),
>     nir_lower_drsq = (1 << 2),
>     nir_lower_dtrunc = (1 << 3),
> +   nir_lower_dfloor = (1 << 4),
>  } nir_lower_doubles_options;
>
>  void nir_lower_doubles(nir_shader *shader, nir_lower_doubles_options
> options);
> diff --git a/src/compiler/nir/nir_lower_double_ops.c
> b/src/compiler/nir/nir_lower_double_ops.c
> index 9eec858..e1ec6da 100644
> --- a/src/compiler/nir/nir_lower_double_ops.c
> +++ b/src/compiler/nir/nir_lower_double_ops.c
> @@ -377,6 +377,27 @@ lower_trunc(nir_builder *b, nir_ssa_def *src)
>     return nir_pack_double_2x32_split(b, new_src_lo, new_src_hi);
>  }
>
> +static nir_ssa_def *
> +lower_floor(nir_builder *b, nir_ssa_def *src)
> +{
> +   /*
> +    * For x >= 0, floor(x) = trunc(x)
> +    * For x < 0,
> +    *    - if x is integer, floor(x) = x
> +    *    - otherwise, floor(x) = trunc(x) - 1
> +    */
> +   nir_ssa_def *tr = nir_ftrunc(b, src);
> +   return nir_bcsel(b,
> +                    nir_fge(b, src, nir_imm_double(b, 0.0)),
> +                    tr,
> +                    nir_bcsel(b,
> +                              nir_fne(b,
> +                                      nir_fsub(b, src, tr),
> +                                      nir_imm_double(b, 0.0)),
>

As an aside, you can just as easily check "x is integer" by "x ==
truc(x)".  That might be simpler.  Same goes for ceil().


> +                              nir_fsub(b, tr, nir_imm_double(b, 1.0)),
> +                              src));
> +}
> +
>  static void
>  lower_doubles_instr(nir_alu_instr *instr, nir_lower_doubles_options
> options)
>  {
> @@ -405,6 +426,11 @@ lower_doubles_instr(nir_alu_instr *instr,
> nir_lower_doubles_options options)
>           return;
>        break;
>
> +   case nir_op_ffloor:
> +      if (!(options & nir_lower_dfloor))
> +         return;
> +      break;
> +
>     default:
>        return;
>     }
> @@ -431,6 +457,9 @@ lower_doubles_instr(nir_alu_instr *instr,
> nir_lower_doubles_options options)
>     case nir_op_ftrunc:
>        result = lower_trunc(&bld, src);
>        break;
> +   case nir_op_ffloor:
> +      result = lower_floor(&bld, src);
> +      break;
>     default:
>        unreachable("unhandled opcode");
>     }
> --
> 2.5.0
>
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