1 /*
2 * Copyright © 2015 Red Hat
3 * Copyright © 2016 Intel Corporation
4 *
5 * Permission is hereby granted, free of charge, to any person obtaining a
6 * copy of this software and associated documentation files (the "Software"),
7 * to deal in the Software without restriction, including without limitation
8 * the rights to use, copy, modify, merge, publish, distribute, sublicense,
9 * and/or sell copies of the Software, and to permit persons to whom the
10 * Software is furnished to do so, subject to the following conditions:
11 *
12 * The above copyright notice and this permission notice (including the next
13 * paragraph) shall be included in all copies or substantial portions of the
14 * Software.
15 *
16 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
17 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
18 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
19 * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
20 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
21 * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
22 * IN THE SOFTWARE.
23 */
24
25 #include "nir.h"
26 #include "nir_builder.h"
27
28 /**
29 * This pass adds sample position to gl_FragCoord, intended for Vulkan drivers
30 * on hardware which provides an integer pixel center. Vulkan mandates that the
31 * pixel center must be half-integer, and also that the coordinate system's
32 * origin must be upper left. This means that there's no need for a uniform - we
33 * can always just add a constant. In the case that sample shading is enabled,
34 * Vulkan expects FragCoord to include sample positions.
35 *
36 * Run before nir_lower_io().
37 *
38 * For a more full featured pass, consider using nir_lower_wpos_ytransform(),
39 * which can handle pixel center integer / half integer, and origin lower
40 * left / upper left transformations.
41 */
42
43 static bool
lower_wpos_center_instr(nir_builder * b,nir_intrinsic_instr * intr,void * data)44 lower_wpos_center_instr(nir_builder *b, nir_intrinsic_instr *intr, void *data)
45 {
46 if (intr->intrinsic != nir_intrinsic_load_frag_coord)
47 return false;
48
49 nir_def *wpos = &intr->def;
50 b->cursor = nir_after_instr(&intr->instr);
51
52 nir_def *spos = nir_load_sample_pos_or_center(b);
53 wpos = nir_fadd(b, wpos, nir_pad_vector_imm_int(b, spos, 0, 4));
54
55 nir_def_rewrite_uses_after(&intr->def, wpos, wpos->parent_instr);
56 return true;
57 }
58
59 bool
nir_lower_wpos_center(nir_shader * shader)60 nir_lower_wpos_center(nir_shader *shader)
61 {
62 assert(shader->info.stage == MESA_SHADER_FRAGMENT);
63
64 return nir_shader_intrinsics_pass(shader, lower_wpos_center_instr,
65 nir_metadata_control_flow,
66 NULL);
67 }
68