On Wed, May 30, 2018 at 4:25 PM Jason Ekstrand <ja...@jlekstrand.net> wrote:
>
> On g4x through Sandy Bridge, src1 (the coordinates) of the PLN
> instruction is required to be an even register number. When it's odd
> (which can happen with SIMD32), we have to emit a LINE+MAC combination
> instead. Unfortunately, we can't just fall through to the gen4 case
> because the input registers are still set up for PLN which lays out the
> four src1 registers differently in SIMD16 than LINE.
>
> v2 (Jason Ekstrand):
> - Take advantage of both accumulators and emit LINE LINE MAC MAC
> (Based on a patch from Francisco Jerez)
> - Unify the gen4 and gen4x-6 cases using a loop
>
> v3 (Jason Ekstrand):
> - Don't unify gen4 with gen4x-6 as this turns out to be more fragile
> than first thought without reworking the gen4 barycentric coordinate
> layout.
> ---
> src/intel/compiler/brw_fs_generator.cpp | 63
> ++++++++++++++++++++++++++++-----
> src/intel/compiler/brw_shader.cpp | 3 +-
> 2 files changed, 56 insertions(+), 10 deletions(-)
>
> diff --git a/src/intel/compiler/brw_fs_generator.cpp
> b/src/intel/compiler/brw_fs_generator.cpp
> index 548a208..906c9c4 100644
> --- a/src/intel/compiler/brw_fs_generator.cpp
> +++ b/src/intel/compiler/brw_fs_generator.cpp
> @@ -761,16 +761,61 @@ fs_generator::generate_linterp(fs_inst *inst,
>
> return true;
> } else if (devinfo->has_pln) {
> - /* From the Sandy Bridge PRM Vol. 4, Pt. 2, Section 8.3.53, "Plane":
> - *
> - * "[DevSNB]:<src1> must be even register aligned.
> - *
> - * This restriction is lifted on Ivy Bridge.
> - */
> - assert(devinfo->gen >= 7 || (delta_x.nr & 1) == 0);
> - brw_PLN(p, dst, interp, delta_x);
> + if (devinfo->gen <= 6 && (delta_x.nr & 1) != 0) {
> + /* From the Sandy Bridge PRM Vol. 4, Pt. 2, Section 8.3.53, "Plane":
> + *
> + * "[DevSNB]:<src1> must be even register aligned.
> + *
> + * This restriction is lifted on Ivy Bridge.
> + *
> + * This means that we need to split PLN into LINE+MAC on-the-fly.
> + * Unfortunately, the inputs are laid out for PLN and not LIN+MAC so
s/LIN/LINE/
Reviewed-by: Matt Turner <matts...@gmail.com>
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