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
55static nir_variable *
56get_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
80static void
81lower_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 = nir_src_for_ssa(texcoord);
100
101   nir_ssa_dest_init(&tex->instr, &tex->dest, 4, 32, NULL);
102   nir_builder_instr_insert(b, &tex->instr);
103
104   /* kill if tex != 0.0.. take .x or .w channel according to format: */
105   cond = nir_f2b(b, nir_channel(b, &tex->dest.ssa,
106                  options->swizzle_xxxx ? 0 : 3));
107
108   discard = nir_intrinsic_instr_create(shader, nir_intrinsic_discard_if);
109   discard->src[0] = nir_src_for_ssa(cond);
110   nir_builder_instr_insert(b, &discard->instr);
111
112   shader->info->fs.uses_discard = true;
113}
114
115static void
116lower_bitmap_impl(nir_function_impl *impl,
117                  const nir_lower_bitmap_options *options)
118{
119   nir_builder b;
120
121   nir_builder_init(&b, impl);
122   b.cursor = nir_before_cf_list(&impl->body);
123
124   lower_bitmap(impl->function->shader, &b, options);
125
126   nir_metadata_preserve(impl, nir_metadata_block_index |
127                               nir_metadata_dominance);
128}
129
130void
131nir_lower_bitmap(nir_shader *shader,
132                 const nir_lower_bitmap_options *options)
133{
134   assert(shader->stage == MESA_SHADER_FRAGMENT);
135
136   lower_bitmap_impl(nir_shader_get_entrypoint(shader), options);
137}
138