1 /*
2 * Copyright © 2014 Intel Corporation
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 * Jason Ekstrand (jason@jlekstrand.net)
25 *
26 */
27
28 #include "nir.h"
29
30 /*
31 * This pass lowers the neg, abs, and sat operations to source modifiers on
32 * ALU operations to make things nicer for the backend. It's just much
33 * easier to not have them when we're doing optimizations.
34 */
35
36 static bool
nir_lower_to_source_mods_block(nir_block * block)37 nir_lower_to_source_mods_block(nir_block *block)
38 {
39 nir_foreach_instr(instr, block) {
40 if (instr->type != nir_instr_type_alu)
41 continue;
42
43 nir_alu_instr *alu = nir_instr_as_alu(instr);
44
45 for (unsigned i = 0; i < nir_op_infos[alu->op].num_inputs; i++) {
46 if (!alu->src[i].src.is_ssa)
47 continue;
48
49 if (alu->src[i].src.ssa->parent_instr->type != nir_instr_type_alu)
50 continue;
51
52 nir_alu_instr *parent = nir_instr_as_alu(alu->src[i].src.ssa->parent_instr);
53
54 if (parent->dest.saturate)
55 continue;
56
57 switch (nir_alu_type_get_base_type(nir_op_infos[alu->op].input_types[i])) {
58 case nir_type_float:
59 if (parent->op != nir_op_fmov)
60 continue;
61 break;
62 case nir_type_int:
63 if (parent->op != nir_op_imov)
64 continue;
65 break;
66 default:
67 continue;
68 }
69
70 /* We can only do a rewrite if the source we are copying is SSA.
71 * Otherwise, moving the read might invalidly reorder reads/writes
72 * on a register.
73 */
74 if (!parent->src[0].src.is_ssa)
75 continue;
76
77 nir_instr_rewrite_src(instr, &alu->src[i].src, parent->src[0].src);
78 if (alu->src[i].abs) {
79 /* abs trumps both neg and abs, do nothing */
80 } else {
81 alu->src[i].negate = (alu->src[i].negate != parent->src[0].negate);
82 alu->src[i].abs |= parent->src[0].abs;
83 }
84
85 for (int j = 0; j < 4; ++j) {
86 if (!nir_alu_instr_channel_used(alu, i, j))
87 continue;
88 alu->src[i].swizzle[j] = parent->src[0].swizzle[alu->src[i].swizzle[j]];
89 }
90
91 if (list_empty(&parent->dest.dest.ssa.uses) &&
92 list_empty(&parent->dest.dest.ssa.if_uses))
93 nir_instr_remove(&parent->instr);
94 }
95
96 switch (alu->op) {
97 case nir_op_fsat:
98 alu->op = nir_op_fmov;
99 alu->dest.saturate = true;
100 break;
101 case nir_op_ineg:
102 alu->op = nir_op_imov;
103 alu->src[0].negate = !alu->src[0].negate;
104 break;
105 case nir_op_fneg:
106 alu->op = nir_op_fmov;
107 alu->src[0].negate = !alu->src[0].negate;
108 break;
109 case nir_op_iabs:
110 alu->op = nir_op_imov;
111 alu->src[0].abs = true;
112 alu->src[0].negate = false;
113 break;
114 case nir_op_fabs:
115 alu->op = nir_op_fmov;
116 alu->src[0].abs = true;
117 alu->src[0].negate = false;
118 break;
119 default:
120 break;
121 }
122
123 /* We've covered sources. Now we're going to try and saturate the
124 * destination if we can.
125 */
126
127 if (!alu->dest.dest.is_ssa)
128 continue;
129
130 /* We can only saturate float destinations */
131 if (nir_alu_type_get_base_type(nir_op_infos[alu->op].output_type) !=
132 nir_type_float)
133 continue;
134
135 if (!list_empty(&alu->dest.dest.ssa.if_uses))
136 continue;
137
138 bool all_children_are_sat = true;
139 nir_foreach_use(child_src, &alu->dest.dest.ssa) {
140 assert(child_src->is_ssa);
141 nir_instr *child = child_src->parent_instr;
142 if (child->type != nir_instr_type_alu) {
143 all_children_are_sat = false;
144 continue;
145 }
146
147 nir_alu_instr *child_alu = nir_instr_as_alu(child);
148 if (child_alu->src[0].negate || child_alu->src[0].abs) {
149 all_children_are_sat = false;
150 continue;
151 }
152
153 if (child_alu->op != nir_op_fsat &&
154 !(child_alu->op == nir_op_fmov && child_alu->dest.saturate)) {
155 all_children_are_sat = false;
156 continue;
157 }
158 }
159
160 if (!all_children_are_sat)
161 continue;
162
163 alu->dest.saturate = true;
164
165 nir_foreach_use(child_src, &alu->dest.dest.ssa) {
166 assert(child_src->is_ssa);
167 nir_alu_instr *child_alu = nir_instr_as_alu(child_src->parent_instr);
168
169 child_alu->op = nir_op_fmov;
170 child_alu->dest.saturate = false;
171 /* We could propagate the dest of our instruction to the
172 * destinations of the uses here. However, one quick round of
173 * copy propagation will clean that all up and then we don't have
174 * the complexity.
175 */
176 }
177 }
178
179 return true;
180 }
181
182 void
nir_lower_to_source_mods(nir_shader * shader)183 nir_lower_to_source_mods(nir_shader *shader)
184 {
185 nir_foreach_function(function, shader) {
186 if (function->impl) {
187 nir_foreach_block(block, function->impl) {
188 nir_lower_to_source_mods_block(block);
189 }
190 }
191 }
192 }
193