1 /*
2 * Copyright 2019 Advanced Micro Devices, Inc.
3 * Copyright 2021 Valve 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
26 #include "ac_nir.h"
27 #include "nir_builder.h"
28
29 /* This code is adapted from ac_llvm_cull.c, hence the copyright to AMD. */
30
31 typedef struct
32 {
33 nir_ssa_def *w_reflection;
34 nir_ssa_def *w_accepted;
35 nir_ssa_def *all_w_positive;
36 nir_ssa_def *any_w_negative;
37 } position_w_info;
38
39 static void
analyze_position_w(nir_builder * b,nir_ssa_def * pos[3][4],position_w_info * w_info)40 analyze_position_w(nir_builder *b, nir_ssa_def *pos[3][4], position_w_info *w_info)
41 {
42 nir_ssa_def *all_w_negative = nir_imm_bool(b, true);
43
44 w_info->w_reflection = nir_imm_bool(b, false);
45 w_info->any_w_negative = nir_imm_bool(b, false);
46
47 for (unsigned i = 0; i < 3; ++i) {
48 nir_ssa_def *neg_w = nir_flt(b, pos[i][3], nir_imm_float(b, 0.0f));
49 w_info->w_reflection = nir_ixor(b, neg_w, w_info->w_reflection);
50 w_info->any_w_negative = nir_ior(b, neg_w, w_info->any_w_negative);
51 all_w_negative = nir_iand(b, neg_w, all_w_negative);
52 }
53
54 w_info->all_w_positive = nir_inot(b, w_info->any_w_negative);
55 w_info->w_accepted = nir_inot(b, all_w_negative);
56 }
57
58 static nir_ssa_def *
cull_face(nir_builder * b,nir_ssa_def * pos[3][4],const position_w_info * w_info)59 cull_face(nir_builder *b, nir_ssa_def *pos[3][4], const position_w_info *w_info)
60 {
61 nir_ssa_def *det_t0 = nir_fsub(b, pos[2][0], pos[0][0]);
62 nir_ssa_def *det_t1 = nir_fsub(b, pos[1][1], pos[0][1]);
63 nir_ssa_def *det_t2 = nir_fsub(b, pos[0][0], pos[1][0]);
64 nir_ssa_def *det_t3 = nir_fsub(b, pos[0][1], pos[2][1]);
65 nir_ssa_def *det_p0 = nir_fmul(b, det_t0, det_t1);
66 nir_ssa_def *det_p1 = nir_fmul(b, det_t2, det_t3);
67 nir_ssa_def *det = nir_fsub(b, det_p0, det_p1);
68
69 det = nir_bcsel(b, w_info->w_reflection, nir_fneg(b, det), det);
70
71 nir_ssa_def *front_facing_cw = nir_flt(b, det, nir_imm_float(b, 0.0f));
72 nir_ssa_def *front_facing_ccw = nir_flt(b, nir_imm_float(b, 0.0f), det);
73 nir_ssa_def *ccw = nir_load_cull_ccw_amd(b);
74 nir_ssa_def *front_facing = nir_bcsel(b, ccw, front_facing_ccw, front_facing_cw);
75 nir_ssa_def *cull_front = nir_load_cull_front_face_enabled_amd(b);
76 nir_ssa_def *cull_back = nir_load_cull_back_face_enabled_amd(b);
77
78 nir_ssa_def *face_culled = nir_bcsel(b, front_facing, cull_front, cull_back);
79
80 /* Don't reject NaN and +/-infinity, these are tricky.
81 * Just trust fixed-function HW to handle these cases correctly.
82 */
83 face_culled = nir_iand(b, face_culled, nir_fisfinite(b, det));
84
85 return nir_inot(b, face_culled);
86 }
87
88 static nir_ssa_def *
cull_bbox(nir_builder * b,nir_ssa_def * pos[3][4],nir_ssa_def * accepted,const position_w_info * w_info)89 cull_bbox(nir_builder *b, nir_ssa_def *pos[3][4], nir_ssa_def *accepted, const position_w_info *w_info)
90 {
91 nir_ssa_def *bbox_accepted = NULL;
92 nir_ssa_def *try_cull_bbox = nir_iand(b, accepted, w_info->all_w_positive);
93
94 nir_if *if_cull_bbox = nir_push_if(b, try_cull_bbox);
95 {
96 nir_ssa_def *bbox_min[3] = {0}, *bbox_max[3] = {0};
97
98 for (unsigned chan = 0; chan < 2; ++chan) {
99 bbox_min[chan] = nir_fmin(b, pos[0][chan], nir_fmin(b, pos[1][chan], pos[2][chan]));
100 bbox_max[chan] = nir_fmax(b, pos[0][chan], nir_fmax(b, pos[1][chan], pos[2][chan]));
101 }
102
103 nir_ssa_def *vp_scale[2] = { nir_load_viewport_x_scale(b), nir_load_viewport_y_scale(b), };
104 nir_ssa_def *vp_translate[2] = { nir_load_viewport_x_offset(b), nir_load_viewport_y_offset(b), };
105 nir_ssa_def *prim_outside_view = nir_imm_false(b);
106
107 /* Frustrum culling - eliminate triangles that are fully outside the view. */
108 for (unsigned chan = 0; chan < 2; ++chan) {
109 prim_outside_view = nir_ior(b, prim_outside_view, nir_flt(b, bbox_max[chan], nir_imm_float(b, -1.0f)));
110 prim_outside_view = nir_ior(b, prim_outside_view, nir_flt(b, nir_imm_float(b, 1.0f), bbox_min[chan]));
111 }
112
113 nir_ssa_def *prim_is_small = NULL;
114 nir_ssa_def *prim_is_small_else = nir_imm_false(b);
115
116 /* Small primitive filter - eliminate triangles that are too small to affect a sample. */
117 nir_if *if_cull_small_prims = nir_push_if(b, nir_load_cull_small_primitives_enabled_amd(b));
118 {
119 nir_ssa_def *small_prim_precision = nir_load_cull_small_prim_precision_amd(b);
120 prim_is_small = nir_imm_false(b);
121
122 for (unsigned chan = 0; chan < 2; ++chan) {
123 /* Convert the position to screen-space coordinates. */
124 nir_ssa_def *min = nir_ffma(b, bbox_min[chan], vp_scale[chan], vp_translate[chan]);
125 nir_ssa_def *max = nir_ffma(b, bbox_max[chan], vp_scale[chan], vp_translate[chan]);
126
127 /* Scale the bounding box according to precision. */
128 min = nir_fsub(b, min, small_prim_precision);
129 max = nir_fadd(b, max, small_prim_precision);
130
131 /* Determine if the bbox intersects the sample point, by checking if the min and max round to the same int. */
132 min = nir_fround_even(b, min);
133 max = nir_fround_even(b, max);
134
135 nir_ssa_def *rounded_to_eq = nir_feq(b, min, max);
136 prim_is_small = nir_ior(b, prim_is_small, rounded_to_eq);
137 }
138 }
139 nir_pop_if(b, if_cull_small_prims);
140
141 prim_is_small = nir_if_phi(b, prim_is_small, prim_is_small_else);
142 nir_ssa_def *prim_invisible = nir_ior(b, prim_outside_view, prim_is_small);
143
144 bbox_accepted = nir_inot(b, prim_invisible);
145 }
146 nir_pop_if(b, if_cull_bbox);
147 return nir_if_phi(b, bbox_accepted, accepted);
148 }
149
150 nir_ssa_def *
ac_nir_cull_triangle(nir_builder * b,nir_ssa_def * initially_accepted,nir_ssa_def * pos[3][4])151 ac_nir_cull_triangle(nir_builder *b,
152 nir_ssa_def *initially_accepted,
153 nir_ssa_def *pos[3][4])
154 {
155 position_w_info w_info = {0};
156 analyze_position_w(b, pos, &w_info);
157
158 nir_ssa_def *accepted = initially_accepted;
159 accepted = nir_iand(b, accepted, w_info.w_accepted);
160 accepted = nir_iand(b, accepted, cull_face(b, pos, &w_info));
161 accepted = nir_iand(b, accepted, cull_bbox(b, pos, accepted, &w_info));
162
163 return accepted;
164 }
165