On Thursday, December 1, 2016 8:53:19 AM PST Iago Toral Quiroga wrote:
> This is ported from the Intel lowering pass that we use with GLSL IR.
> This takes care of lowering texture gradients on shadow samplers other
> than cube maps. Intel hardware requires this for gen < 8.
> ---
> src/compiler/nir/nir.h | 7 +++++++
> src/compiler/nir/nir_lower_tex.c | 40
> ++++++++++++++++++++++++++++++++++++++++
> 2 files changed, 47 insertions(+)
>
> diff --git a/src/compiler/nir/nir.h b/src/compiler/nir/nir.h
> index ed388c6..d494d5f 100644
> --- a/src/compiler/nir/nir.h
> +++ b/src/compiler/nir/nir.h
> @@ -2437,6 +2437,13 @@ typedef struct nir_lower_tex_options {
> * If true, lower nir_texop_txd on cube maps with nir_texop_txl.
> */
> bool lower_txd_cube_map;
> +
> + /**
> + * If true, lower nir_texop_txd on shadow samplers (except cube maps)
> + * with nir_texop_txl. Notice that cube map shadow samplers are lowered
> + * with lower_txd_cube_map.
> + */
> + bool lower_txd_shadow;
> } nir_lower_tex_options;
>
> bool nir_lower_tex(nir_shader *shader,
> diff --git a/src/compiler/nir/nir_lower_tex.c
> b/src/compiler/nir/nir_lower_tex.c
> index c7c3db2..d5ea509 100644
> --- a/src/compiler/nir/nir_lower_tex.c
> +++ b/src/compiler/nir/nir_lower_tex.c
> @@ -556,6 +556,40 @@ lower_gradient_cube_map(nir_builder *b, nir_tex_instr
> *tex)
> }
>
> static void
> +lower_gradient_shadow(nir_builder *b, nir_tex_instr *tex)
> +{
> + assert(tex->sampler_dim != GLSL_SAMPLER_DIM_CUBE);
> + assert(tex->is_shadow);
> + assert(tex->op == nir_texop_txd);
> + assert(tex->dest.is_ssa);
> +
> + /* Use textureSize() to get the width and height of LOD 0 */
> + nir_ssa_def *size = get_texture_size(b, tex);
> +
> + /* Scale the gradients by width and height. Effectively, the incoming
> + * gradients are s'(x,y), t'(x,y), and r'(x,y) from equation 3.19 in the
> + * GL 3.0 spec; we want u'(x,y), which is w_t * s'(x,y).
> + */
> + nir_ssa_def *dPdx = nir_fmul(b, tex->src[2].src.ssa, size);
> + nir_ssa_def *dPdy = nir_fmul(b, tex->src[3].src.ssa, size);
NIR texture sources aren't guaranteed to be in any particular order
(it's kind of annoying)...you should instead do:
nir_ssa_def *dPdx;
nir_ssa_def *dPdy;
for (unsigned i = 0; i < tex->num_srcs; i++) {
switch (tex->src[i].src_type) {
case nir_tex_src_ddx:
dPdx = nir_fmul(b, tex->src[i].src.ssa, size);
break;
case nir_tex_src_ddy:
dPdy = nir_fmul(b, tex->src[i].src.ssa, size);
break;
default:
break;
}
}
Same comment on patch two. Maybe make a get_ddx_ddy() helper?
> +
> + nir_ssa_def *rho;
> + if (dPdx->num_components == 1) {
> + rho = nir_fmax(b, nir_fabs(b, dPdx), nir_fabs(b, dPdy));
> + } else {
> + rho = nir_fmax(b,
> + nir_fsqrt(b, nir_fdot(b, dPdx, dPdx)),
> + nir_fsqrt(b, nir_fdot(b, dPdy, dPdy)));
> + }
> +
> + /* lod = log2(rho). We're ignoring GL state biases for now. */
> + nir_ssa_def *lod = nir_flog2(b, rho);
> +
> + /* Replace the gradient instruction with an equivalent lod instruction */
> + replace_gradient_with_lod(b, lod, tex);
> +}
> +
> +static void
> saturate_src(nir_builder *b, nir_tex_instr *tex, unsigned sat_mask)
> {
> b->cursor = nir_before_instr(&tex->instr);
> @@ -786,6 +820,12 @@ nir_lower_tex_block(nir_block *block, nir_builder *b,
> lower_gradient_cube_map(b, tex);
> progress = true;
> }
> +
> + if (tex->op == nir_texop_txd && options->lower_txd_shadow &&
> + tex->is_shadow && tex->sampler_dim != GLSL_SAMPLER_DIM_CUBE) {
> + lower_gradient_shadow(b, tex);
> + progress = true;
> + }
This seems a bit odd to me - if a driver sets options->lower_txd_shadow
but not options->lower_txd_cube_map, then textureGrad(samplerCubeShadow, ...)
would not be lowered. I would sort of expect that case to be lowered if
either option is set.
I suppose it's not a problem in practice, as we set both, but it might
be nice to fix this anyway.
With the ddx/ddy source finding fixed in both patches, the series is:
Reviewed-by: Kenneth Graunke <kenn...@whitecape.org>
> }
>
> return progress;
>
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