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 * Run before nir_lower_io.
53 */
54
55 static nir_variable *
get_texcoord(nir_shader * shader)56 get_texcoord(nir_shader *shader)
57 {
58 nir_variable *texcoord = NULL;
59
60 /* find gl_TexCoord, if it exists: */
61 nir_foreach_variable(var, &shader->inputs) {
62 if (var->data.location == VARYING_SLOT_TEX0) {
63 texcoord = var;
64 break;
65 }
66 }
67
68 /* otherwise create it: */
69 if (texcoord == NULL) {
70 texcoord = nir_variable_create(shader,
71 nir_var_shader_in,
72 glsl_vec4_type(),
73 "gl_TexCoord");
74 texcoord->data.location = VARYING_SLOT_TEX0;
75 }
76
77 return texcoord;
78 }
79
80 static void
lower_bitmap(nir_shader * shader,nir_builder * b,const nir_lower_bitmap_options * options)81 lower_bitmap(nir_shader *shader, nir_builder *b,
82 const nir_lower_bitmap_options *options)
83 {
84 nir_ssa_def *texcoord;
85 nir_tex_instr *tex;
86 nir_ssa_def *cond;
87 nir_intrinsic_instr *discard;
88
89 texcoord = nir_load_var(b, get_texcoord(shader));
90
91 tex = nir_tex_instr_create(shader, 1);
92 tex->op = nir_texop_tex;
93 tex->sampler_dim = GLSL_SAMPLER_DIM_2D;
94 tex->coord_components = 2;
95 tex->sampler_index = options->sampler;
96 tex->texture_index = options->sampler;
97 tex->dest_type = nir_type_float;
98 tex->src[0].src_type = nir_tex_src_coord;
99 tex->src[0].src =
100 nir_src_for_ssa(nir_channels(b, texcoord,
101 (1 << tex->coord_components) - 1));
102
103 nir_ssa_dest_init(&tex->instr, &tex->dest, 4, 32, NULL);
104 nir_builder_instr_insert(b, &tex->instr);
105
106 /* kill if tex != 0.0.. take .x or .w channel according to format: */
107 cond = nir_f2b(b, nir_channel(b, &tex->dest.ssa,
108 options->swizzle_xxxx ? 0 : 3));
109
110 discard = nir_intrinsic_instr_create(shader, nir_intrinsic_discard_if);
111 discard->src[0] = nir_src_for_ssa(cond);
112 nir_builder_instr_insert(b, &discard->instr);
113
114 shader->info.fs.uses_discard = true;
115 }
116
117 static void
lower_bitmap_impl(nir_function_impl * impl,const nir_lower_bitmap_options * options)118 lower_bitmap_impl(nir_function_impl *impl,
119 const nir_lower_bitmap_options *options)
120 {
121 nir_builder b;
122
123 nir_builder_init(&b, impl);
124 b.cursor = nir_before_cf_list(&impl->body);
125
126 lower_bitmap(impl->function->shader, &b, options);
127
128 nir_metadata_preserve(impl, nir_metadata_block_index |
129 nir_metadata_dominance);
130 }
131
132 void
nir_lower_bitmap(nir_shader * shader,const nir_lower_bitmap_options * options)133 nir_lower_bitmap(nir_shader *shader,
134 const nir_lower_bitmap_options *options)
135 {
136 assert(shader->info.stage == MESA_SHADER_FRAGMENT);
137
138 lower_bitmap_impl(nir_shader_get_entrypoint(shader), options);
139 }
140