1 /*
2 * Copyright © 2020 Mike Blumenkrantz
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
20 * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
21 * IN THE SOFTWARE.
22 *
23 * Authors:
24 * Mike Blumenkrantz <michael.blumenkrantz@gmail.com>
25 */
26
27 #include "nir.h"
28 #include "nir_builder.h"
29
30
31 /**
32 * This pass uses the enabled clip planes from the rasterizer state to rewrite
33 * vertex shader store operations and store a 0 to the corresponding gl_ClipDistance[n]
34 * value if the plane is disabled
35 */
36
37 /* recursively nest if/else blocks until we get to an array index,
38 * then overwrite it if that plane isn't enabled
39 */
40 static void
recursive_if_chain(nir_builder * b,nir_deref_instr * deref,nir_ssa_def * value,unsigned clip_plane_enable,nir_ssa_def * index,unsigned start,unsigned end)41 recursive_if_chain(nir_builder *b, nir_deref_instr *deref, nir_ssa_def *value, unsigned clip_plane_enable, nir_ssa_def *index, unsigned start, unsigned end)
42 {
43 if (start == end - 1) {
44 /* store the original value again if the clip plane is enabled */
45 if (clip_plane_enable & (1 << start))
46 nir_store_deref(b, deref, value, 1 << start);
47 else
48 nir_store_deref(b, deref, nir_imm_int(b, 0), 1 << start);
49 return;
50 }
51
52 unsigned mid = start + (end - start) / 2;
53 nir_push_if(b, nir_ilt(b, index, nir_imm_int(b, mid)));
54 recursive_if_chain(b, deref, value, clip_plane_enable, index, start, mid);
55 nir_push_else(b, NULL);
56 recursive_if_chain(b, deref, value, clip_plane_enable, index, mid, end);
57 nir_pop_if(b, NULL);
58 }
59
60 /* vulkan (and some drivers) provides no concept of enabling clip planes through api,
61 * so we rewrite disabled clip planes to a zero value in order to disable them
62 */
63 static bool
lower_clip_plane_store(nir_intrinsic_instr * instr,unsigned clip_plane_enable,nir_builder * b)64 lower_clip_plane_store(nir_intrinsic_instr *instr, unsigned clip_plane_enable, nir_builder *b)
65 {
66 nir_variable *out;
67 unsigned plane;
68
69 if (instr->intrinsic != nir_intrinsic_store_deref)
70 return false;
71
72 nir_deref_instr *deref = nir_src_as_deref(instr->src[0]);
73
74 out = nir_deref_instr_get_variable(deref);
75 if ((out->data.location != VARYING_SLOT_CLIP_DIST0 &&
76 out->data.location != VARYING_SLOT_CLIP_DIST1) ||
77 out->data.mode != nir_var_shader_out)
78 return false;
79
80 b->cursor = nir_after_instr(&instr->instr);
81 if (deref->deref_type == nir_deref_type_var) {
82 int wrmask = nir_intrinsic_write_mask(instr);
83
84 nir_ssa_def *components[4];
85 int start = out->data.location == VARYING_SLOT_CLIP_DIST1 ? 4 : 0;
86 /* rewrite components as zeroes for planes that aren't enabled */
87 for (int i = 0; i < 4; i++) {
88 if (wrmask & (1 << i)) {
89 if (!(clip_plane_enable & (1 << (start + i))))
90 components[i] = nir_imm_int(b, 0);
91 else
92 components[i] = nir_channel(b, nir_ssa_for_src(b, instr->src[1], nir_src_num_components(instr->src[1])), i);
93 } else
94 components[i] = nir_ssa_undef(b, 1, 32);
95 }
96 nir_store_deref(b, deref, nir_vec(b, components, instr->num_components), wrmask);
97 } else if (nir_src_is_const(deref->arr.index)) {
98 /* storing using a constant index */
99 plane = nir_src_as_uint(deref->arr.index);
100 /* no need to make changes if the clip plane is enabled */
101 if (clip_plane_enable & (1 << plane))
102 return false;
103
104 assert(nir_intrinsic_write_mask(instr) == 1);
105 nir_store_deref(b, deref, nir_imm_int(b, 0), 1);
106 } else {
107 /* storing using a variable index */
108 nir_ssa_def *index = nir_ssa_for_src(b, deref->arr.index, 1);
109 unsigned length = glsl_get_length(nir_deref_instr_parent(deref)->type);
110
111 recursive_if_chain(b, deref, instr->src[1].ssa, clip_plane_enable, index, 0, length);
112 }
113 nir_instr_remove(&instr->instr);
114 return true;
115 }
116
117 bool
nir_lower_clip_disable(nir_shader * shader,unsigned clip_plane_enable)118 nir_lower_clip_disable(nir_shader *shader, unsigned clip_plane_enable)
119 {
120 bool progress = false;
121
122 /* if all user planes are enabled in API that are written in the array, always ignore;
123 * this explicitly covers the 2x vec4 case
124 */
125 if (clip_plane_enable == u_bit_consecutive(0, shader->info.clip_distance_array_size))
126 return false;
127
128 nir_foreach_function(function, shader) {
129 if (function->impl) {
130 nir_builder builder;
131 nir_builder_init(&builder, function->impl);
132 nir_foreach_block(block, function->impl) {
133 nir_foreach_instr_safe(instr, block) {
134 if (instr->type == nir_instr_type_intrinsic)
135 progress |= lower_clip_plane_store(nir_instr_as_intrinsic(instr),
136 clip_plane_enable,
137 &builder);
138 }
139 }
140
141 nir_metadata_preserve(function->impl, nir_metadata_block_index | nir_metadata_dominance);
142 }
143 }
144
145 return progress;
146 }
147