1/*
2 * Copyright (C) 2019 Collabora, Ltd.
3 *
4 * Permission is hereby granted, free of charge, to any person obtaining a
5 * copy of this software and associated documentation files (the "Software"),
6 * to deal in the Software without restriction, including without limitation
7 * the rights to use, copy, modify, merge, publish, distribute, sublicense,
8 * and/or sell copies of the Software, and to permit persons to whom the
9 * Software is furnished to do so, subject to the following conditions:
10 *
11 * The above copyright notice and this permission notice (including the next
12 * paragraph) shall be included in all copies or substantial portions of the
13 * Software.
14 *
15 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
16 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
17 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
18 * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
19 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
20 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
21 * SOFTWARE.
22 */
23
24#include "compiler/nir/nir.h"
25#include "compiler/nir/nir_builder.h"
26
27bool midgard_nir_lod_errata(nir_shader *shader);
28
29/* Workarounds errata pertaining to early Midgard chips where the settings for
30 * min_lod/max_lod/lod_bias are ignored in the sampler descriptor when
31 * texturing with a textureLod instruction. The workaround is to load these
32 * constants in as system values and perform the bias/clamp in the shader.
33 */
34
35static bool
36nir_lod_errata_instr(nir_builder *b, nir_instr *instr, void *data)
37{
38        if (instr->type != nir_instr_type_tex)
39                return false;
40
41        nir_tex_instr *tex = nir_instr_as_tex(instr);
42        b->cursor = nir_before_instr(instr);
43
44        /* The errata only applies to textureLod ("TEXGRD") */
45        if (tex->op != nir_texop_txl)
46                return false;
47
48        /* Let's grab the sampler parameters */
49        nir_intrinsic_instr *l = nir_intrinsic_instr_create(b->shader,
50                        nir_intrinsic_load_sampler_lod_parameters_pan);
51        l->num_components = 3;
52        nir_ssa_dest_init(&l->instr, &l->dest, 3, 32, NULL);
53
54        /* TODO: Indirect samplers, separate sampler objects XXX */
55        nir_src idx = nir_src_for_ssa(nir_imm_int(b, tex->texture_index));
56        nir_src_copy(&l->src[0], &idx);
57
58        nir_builder_instr_insert(b, &l->instr);
59        nir_ssa_def *params = &l->dest.ssa;
60
61        /* Extract the individual components */
62        nir_ssa_def *min_lod = nir_channel(b, params, 0);
63        nir_ssa_def *max_lod = nir_channel(b, params, 1);
64        nir_ssa_def *lod_bias = nir_channel(b, params, 2);
65
66        /* Rewrite the LOD with bias/clamps. Order sensitive. */
67        for (unsigned i = 0; i < tex->num_srcs; i++) {
68                if (tex->src[i].src_type != nir_tex_src_lod)
69                        continue;
70
71                nir_ssa_def *lod = nir_ssa_for_src(b, tex->src[i].src, 1);
72
73                nir_ssa_def *biased = nir_fadd(b, lod, lod_bias);
74                nir_ssa_def *clamped = nir_fmin(b,
75                                nir_fmax(b, biased, min_lod), max_lod);
76
77                nir_instr_rewrite_src(&tex->instr, &tex->src[i].src,
78                                nir_src_for_ssa(clamped));
79        }
80
81        return true;
82}
83
84bool
85midgard_nir_lod_errata(nir_shader *shader)
86{
87        return nir_shader_instructions_pass(shader,
88                                            nir_lod_errata_instr,
89                                            nir_metadata_block_index | nir_metadata_dominance,
90                                            NULL);
91}
92