On Wed, May 18, 2016 at 6:00 PM, Kenneth Graunke <kenn...@whitecape.org> wrote:
> ffma is an explicitly fused multiply add with higher precision.
> The optimizer will take care of promoting mul/add to fma when
> it's beneficial to do so.
>
> This fixes failures on Gen4-5 when using this pass, as those platforms
> don't actually implement fma().
hmm, we can't rely on the opt-algebraic pass to do this?
BR,
-R
> Signed-off-by: Kenneth Graunke <kenn...@whitecape.org>
> ---
> src/compiler/nir/nir_lower_wpos_ytransform.c | 20 ++++++++------------
> 1 file changed, 8 insertions(+), 12 deletions(-)
>
> diff --git a/src/compiler/nir/nir_lower_wpos_ytransform.c
> b/src/compiler/nir/nir_lower_wpos_ytransform.c
> index 36e25b9..ccf0fd3 100644
> --- a/src/compiler/nir/nir_lower_wpos_ytransform.c
> +++ b/src/compiler/nir/nir_lower_wpos_ytransform.c
> @@ -123,19 +123,15 @@ emit_wpos_adjustment(lower_wpos_ytransform_state *state,
> * inversion/identity, or the other way around if we're drawing to an FBO.
> */
> if (invert) {
> - /* MAD wpos_temp.y, wpos_input, wpostrans.xxxx, wpostrans.yyyy
> - */
> - wpos_temp_y = nir_ffma(b,
> - nir_channel(b, wpos_temp, 1),
> - nir_channel(b, wpostrans, 0),
> - nir_channel(b, wpostrans, 1));
> + /* wpos_temp.y = wpos_input * wpostrans.xxxx + wpostrans.yyyy */
> + wpos_temp_y = nir_fadd(b, nir_fmul(b, nir_channel(b, wpos_temp, 1),
> + nir_channel(b, wpostrans, 0)),
> + nir_channel(b, wpostrans, 1));
> } else {
> - /* MAD wpos_temp.y, wpos_input, wpostrans.zzzz, wpostrans.wwww
> - */
> - wpos_temp_y = nir_ffma(b,
> - nir_channel(b, wpos_temp, 1),
> - nir_channel(b, wpostrans, 2),
> - nir_channel(b, wpostrans, 3));
> + /* wpos_temp.y = wpos_input * wpostrans.zzzz + wpostrans.wwww */
> + wpos_temp_y = nir_fadd(b, nir_fmul(b, nir_channel(b, wpos_temp, 1),
> + nir_channel(b, wpostrans, 2)),
> + nir_channel(b, wpostrans, 3));
> }
>
> wpos_temp = nir_vec4(b,
> --
> 2.8.2
>
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