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 #include "program/prog_instruction.h"
28
29 /**
30 * This pass adds <0.5, 0.5> to all uses of gl_FragCoord.
31 *
32 * Run before nir_lower_io().
33 *
34 * For a more full featured pass, consider using nir_lower_wpos_ytransform(),
35 * which can handle pixel center integer / half integer, and origin lower
36 * left / upper left transformations.
37 *
38 * This simple pass is primarily intended for use by Vulkan drivers on
39 * hardware which provides an integer pixel center. Vulkan mandates that
40 * the pixel center must be half-integer, and also that the coordinate
41 * system's origin must be upper left. This means that there's no need
42 * for a uniform - we can always just add a constant.
43 */
44
45 static void
add_half_to_fragcoord(nir_builder * b,nir_intrinsic_instr * intr)46 add_half_to_fragcoord(nir_builder *b, nir_intrinsic_instr *intr)
47 {
48 nir_ssa_def *wpos = &intr->dest.ssa;
49
50 assert(intr->dest.is_ssa);
51
52 b->cursor = nir_after_instr(&intr->instr);
53
54 wpos = nir_fadd(b, wpos, nir_imm_vec4(b, 0.5f, 0.5f, 0.0f, 0.0f));
55
56 nir_ssa_def_rewrite_uses_after(&intr->dest.ssa, nir_src_for_ssa(wpos),
57 wpos->parent_instr);
58 }
59
60 static bool
lower_wpos_center_block(nir_builder * b,nir_block * block)61 lower_wpos_center_block(nir_builder *b, nir_block *block)
62 {
63 bool progress = false;
64
65 nir_foreach_instr(instr, block) {
66 if (instr->type == nir_instr_type_intrinsic) {
67 nir_intrinsic_instr *intr = nir_instr_as_intrinsic(instr);
68 if (intr->intrinsic == nir_intrinsic_load_var) {
69 nir_deref_var *dvar = intr->variables[0];
70 nir_variable *var = dvar->var;
71
72 if (var->data.mode == nir_var_shader_in &&
73 var->data.location == VARYING_SLOT_POS) {
74 /* gl_FragCoord should not have array/struct deref's: */
75 assert(dvar->deref.child == NULL);
76 add_half_to_fragcoord(b, intr);
77 progress = true;
78 }
79 }
80 }
81 }
82
83 return progress;
84 }
85
86 bool
nir_lower_wpos_center(nir_shader * shader)87 nir_lower_wpos_center(nir_shader *shader)
88 {
89 bool progress = false;
90 nir_builder b;
91
92 assert(shader->stage == MESA_SHADER_FRAGMENT);
93
94 nir_foreach_function(function, shader) {
95 if (function->impl) {
96 nir_builder_init(&b, function->impl);
97
98 nir_foreach_block(block, function->impl) {
99 progress = lower_wpos_center_block(&b, block) || progress;
100 }
101 nir_metadata_preserve(function->impl, nir_metadata_block_index |
102 nir_metadata_dominance);
103 }
104 }
105
106 return progress;
107 }
108