1/*
2 * Copyright 2018-2019 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 * on the rights to use, copy, modify, merge, publish, distribute, sub
8 * license, and/or sell copies of the Software, and to permit persons to whom
9 * the 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 NON-INFRINGEMENT. IN NO EVENT SHALL
18 * THE AUTHOR(S) AND/OR THEIR SUPPLIERS BE LIABLE FOR ANY CLAIM,
19 * DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR
20 * OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE
21 * USE OR OTHER DEALINGS IN THE SOFTWARE.
22 */
23
24#include "nir_builder.h"
25
26static void
27lower_pos_write(nir_builder *b, struct nir_instr *instr)
28{
29   if (instr->type != nir_instr_type_intrinsic)
30      return;
31
32   nir_intrinsic_instr *intr = nir_instr_as_intrinsic(instr);
33   if (intr->intrinsic != nir_intrinsic_store_deref)
34      return;
35
36   nir_variable *var = nir_intrinsic_get_var(intr, 0);
37   if (var->data.mode != nir_var_shader_out ||
38       var->data.location != VARYING_SLOT_POS)
39      return;
40
41   b->cursor = nir_before_instr(&intr->instr);
42
43   nir_ssa_def *pos = nir_ssa_for_src(b, intr->src[1], 4);
44   nir_ssa_def *def = nir_vec4(b,
45                               nir_channel(b, pos, 0),
46                               nir_channel(b, pos, 1),
47                               nir_fmul_imm(b,
48                                            nir_fadd(b,
49                                                     nir_channel(b, pos, 2),
50                                                     nir_channel(b, pos, 3)),
51                                            0.5),
52                               nir_channel(b, pos, 3));
53   nir_instr_rewrite_src(&intr->instr, intr->src + 1, nir_src_for_ssa(def));
54}
55
56void
57nir_lower_clip_halfz(nir_shader *shader)
58{
59   if (shader->info.stage != MESA_SHADER_VERTEX &&
60       shader->info.stage != MESA_SHADER_GEOMETRY &&
61       shader->info.stage != MESA_SHADER_TESS_EVAL)
62      return;
63
64   nir_foreach_function(function, shader) {
65      if (function->impl) {
66         nir_builder b;
67         nir_builder_init(&b, function->impl);
68
69         nir_foreach_block(block, function->impl) {
70            nir_foreach_instr_safe(instr, block) {
71               lower_pos_write(&b, instr);
72            }
73         }
74
75         nir_metadata_preserve(function->impl, nir_metadata_block_index |
76                                               nir_metadata_dominance);
77      }
78   }
79}
80