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1/*
2 * Copyright © 2015 Red Hat
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 "nir.h"
25#include "nir_builder.h"
26
27/* Lower glBitmap().
28 *
29 * This is based on the logic in st_get_bitmap_shader() in TGSI compiler.
30 * From st_cb_bitmap.c:
31 *
32 * glBitmaps are drawn as textured quads. The user's bitmap pattern
33 * is stored in a texture image. An alpha8 texture format is used.
34 * The fragment shader samples a bit (texel) from the texture, then
35 * discards the fragment if the bit is off.
36 *
37 * Note that we actually store the inverse image of the bitmap to
38 * simplify the fragment program. An "on" bit gets stored as texel=0x0
39 * and an "off" bit is stored as texel=0xff. Then we kill the
40 * fragment if the negated texel value is less than zero.
41 *
42 * Note that the texture format will be, according to what driver supports,
43 * in order of preference (with swizzle):
44 *
45 * I8_UNORM - .xxxx
46 * A8_UNORM - .000x
47 * L8_UNORM - .xxx1
48 *
49 * If L8_UNORM, options->swizzle_xxxx is true. Otherwise we can just use
50 * the .w comp.
51 */
52
53static void
54lower_bitmap(nir_shader *shader, nir_builder *b,
55 const nir_lower_bitmap_options *options)
56{
57 nir_def *texcoord;
58 nir_tex_instr *tex;
59 nir_def *cond;
60
61 nir_def *baryc =
62 nir_load_barycentric_pixel(b, 32, .interp_mode = INTERP_MODE_SMOOTH);
63 texcoord = nir_load_interpolated_input(b, 4, 32, baryc, nir_imm_int(b, 0),
64 .io_semantics.location = VARYING_SLOT_TEX0);
65
66 const struct glsl_type *sampler2D =
67 glsl_sampler_type(GLSL_SAMPLER_DIM_2D, false, false, GLSL_TYPE_FLOAT);
68
69 nir_variable *tex_var =
70 nir_variable_create(shader, nir_var_uniform, sampler2D, "bitmap_tex");
71 tex_var->data.binding = options->sampler;
72 tex_var->data.explicit_binding = true;
73 tex_var->data.how_declared = nir_var_hidden;
74
75 nir_deref_instr *tex_deref = nir_build_deref_var(b, tex_var);
76
77 tex = nir_tex_instr_create(shader, 3);
78 tex->op = nir_texop_tex;
79 tex->sampler_dim = GLSL_SAMPLER_DIM_2D;
80 tex->coord_components = 2;
81 tex->dest_type = nir_type_float32;
82 tex->src[0] = nir_tex_src_for_ssa(nir_tex_src_texture_deref,
83 &tex_deref->def);
84 tex->src[1] = nir_tex_src_for_ssa(nir_tex_src_sampler_deref,
85 &tex_deref->def);
86 tex->src[2] = nir_tex_src_for_ssa(nir_tex_src_coord,
87 nir_trim_vector(b, texcoord, tex->coord_components));
88
89 nir_def_init(&tex->instr, &tex->def, 4, 32);
90 nir_builder_instr_insert(b, &tex->instr);
91
92 /* kill if tex != 0.0.. take .x or .w channel according to format: */
93 cond = nir_fneu_imm(b, nir_channel(b, &tex->def, options->swizzle_xxxx ? 0 : 3),
94 0.0);
95
96 nir_discard_if(b, cond);
97
98 shader->info.fs.uses_discard = true;
99}
100
101static void
102lower_bitmap_impl(nir_function_impl *impl,
103 const nir_lower_bitmap_options *options)
104{
105 nir_builder b = nir_builder_at(nir_before_impl(impl));
106
107 lower_bitmap(impl->function->shader, &b, options);
108
109 nir_metadata_preserve(impl, nir_metadata_control_flow);
110}
111
112bool
113nir_lower_bitmap(nir_shader *shader,
114 const nir_lower_bitmap_options *options)
115{
116 assert(shader->info.stage == MESA_SHADER_FRAGMENT);
117 assert(shader->info.io_lowered);
118
119 lower_bitmap_impl(nir_shader_get_entrypoint(shader), options);
120 return true;
121}