[Mesa-dev] [PATCH 2/3] i965: Add a NIR-based cubemap normalizing pass

[Eric Anholt]

Jason Ekstrand <jason at jlekstrand.net> writes:

> ---
>  src/mesa/drivers/dri/i965/Makefile.sources         |   1 +
>  src/mesa/drivers/dri/i965/brw_nir.h                |   2 +
>  .../drivers/dri/i965/brw_nir_cubemap_normalize.c   | 111 +++++++++++++++++++++
>  3 files changed, 114 insertions(+)
>  create mode 100644 src/mesa/drivers/dri/i965/brw_nir_cubemap_normalize.c

Could this go in src/glsl/nir?  vc4 also lowers cubemaps the same way,
so I might want to use it.

(Probably won't immediately, due to the same "do I really want to make
my rcp that accurate for this operation?  probably not." concern as for
txp).

> diff --git a/src/mesa/drivers/dri/i965/brw_nir_cubemap_normalize.c b/src/mesa/drivers/dri/i965/brw_nir_cubemap_normalize.c
> new file mode 100644
> index 0000000..6464f41
> --- /dev/null
> +++ b/src/mesa/drivers/dri/i965/brw_nir_cubemap_normalize.c
> @@ -0,0 +1,111 @@
> +/*
> + * Copyright © 2015 Intel Corporation
> + *
> + * Permission is hereby granted, free of charge, to any person obtaining a
> + * copy of this software and associated documentation files (the "Software"),
> + * to deal in the Software without restriction, including without limitation
> + * the rights to use, copy, modify, merge, publish, distribute, sublicense,
> + * and/or sell copies of the Software, and to permit persons to whom the
> + * Software is furnished to do so, subject to the following conditions:
> + *
> + * The above copyright notice and this permission notice (including the next
> + * paragraph) shall be included in all copies or substantial portions of the
> + * Software.
> + *
> + * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
> + * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
> + * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
> + * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
> + * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
> + * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
> + * IN THE SOFTWARE.
> + *
> + * Authors:
> + *    Jason Ekstrand <jason at jlekstrand.net>
> + */
> +
> +#include "brw_nir.h"
> +#include "glsl/nir/nir_builder.h"
> +
> +/**
> + * This file implements a NIR lowering pass to perform the normalization of
> + * the cubemap coordinates to have the largest magnitude component be -1.0
> + * or 1.0.  This is based on the old GLSL IR based pass by Eric.
> + */
> +
> +static nir_ssa_def *
> +channel(nir_builder *b, nir_ssa_def *def, int c)
> +{
> +   return nir_swizzle(b, def, (unsigned[4]){c, c, c, c}, 1, false);
> +}
> +
> +static bool
> +cubemap_normalize_block(nir_block *block, void *void_state)
> +{
> +   nir_builder *b = void_state;
> +
> +   nir_foreach_instr(block, instr) {
> +      if (instr->type != nir_instr_type_tex)
> +         continue;
> +
> +      nir_tex_instr *tex = nir_instr_as_tex(instr);
> +      if (tex->sampler_dim != GLSL_SAMPLER_DIM_CUBE)
> +         continue;
> +
> +      nir_builder_insert_before_instr(b, &tex->instr);
> +
> +      for (unsigned i = 0; i < tex->num_srcs; i++) {
> +         if (tex->src[i].src_type != nir_tex_src_coord)
> +            continue;
> +
> +         nir_ssa_def *orig_coord =
> +            nir_ssa_for_src(b, tex->src[i].src, nir_tex_instr_src_size(tex, i));
> +         assert(orig_coord->num_components >= 3);
> +
> +         nir_ssa_def *abs0 = nir_fabs(b, channel(b, orig_coord, 0));
> +         nir_ssa_def *abs1 = nir_fabs(b, channel(b, orig_coord, 1));
> +         nir_ssa_def *abs2 = nir_fabs(b, channel(b, orig_coord, 2));
> +
> +         nir_ssa_def *norm1 = nir_fmax(b, abs0, nir_fmax(b, abs1, abs2));

This could just be:

nir_ssa_def *abs = nir_fabs(b, orig_coord);
nir_ssa_def *norm = nir_fmax(b, channel(b, abs, 0),
                             nir_fmax(b, channel(b, abs, 1),
                                         channel(b, abs, 2)));

right?  Just in case vec4 NIR ends up being a thing.

Other than these little comments,

Reviewed-by: Eric Anholt <eric at anholt.net>
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