1 /*
2 * Copyright © 2016 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
21 * DEALINGS IN THE SOFTWARE.
22 */
23
24 #include "nir.h"
25
26 static void
add_src(nir_src * src,struct set * invariants)27 add_src(nir_src *src, struct set *invariants)
28 {
29 if (src->is_ssa) {
30 _mesa_set_add(invariants, src->ssa);
31 } else {
32 _mesa_set_add(invariants, src->reg.reg);
33 }
34 }
35
36 static bool
add_src_cb(nir_src * src,void * state)37 add_src_cb(nir_src *src, void *state)
38 {
39 add_src(src, state);
40 return true;
41 }
42
43 static bool
dest_is_invariant(nir_dest * dest,struct set * invariants)44 dest_is_invariant(nir_dest *dest, struct set *invariants)
45 {
46 if (dest->is_ssa) {
47 return _mesa_set_search(invariants, &dest->ssa);
48 } else {
49 return _mesa_set_search(invariants, dest->reg.reg);
50 }
51 }
52
53 static void
add_cf_node(nir_cf_node * cf,struct set * invariants)54 add_cf_node(nir_cf_node *cf, struct set *invariants)
55 {
56 if (cf->type == nir_cf_node_if) {
57 nir_if *if_stmt = nir_cf_node_as_if(cf);
58 add_src(&if_stmt->condition, invariants);
59 }
60
61 if (cf->parent)
62 add_cf_node(cf->parent, invariants);
63 }
64
65 static void
add_var(nir_variable * var,struct set * invariants)66 add_var(nir_variable *var, struct set *invariants)
67 {
68 /* Because we pass the result of nir_intrinsic_get_var directly to this
69 * function, it's possible for var to be NULL if, for instance, there's a
70 * cast somewhere in the chain.
71 */
72 if (var != NULL)
73 _mesa_set_add(invariants, var);
74 }
75
76 static bool
var_is_invariant(nir_variable * var,struct set * invariants)77 var_is_invariant(nir_variable *var, struct set * invariants)
78 {
79 /* Because we pass the result of nir_intrinsic_get_var directly to this
80 * function, it's possible for var to be NULL if, for instance, there's a
81 * cast somewhere in the chain.
82 */
83 return var && (var->data.invariant || _mesa_set_search(invariants, var));
84 }
85
86 static void
propagate_invariant_instr(nir_instr * instr,struct set * invariants)87 propagate_invariant_instr(nir_instr *instr, struct set *invariants)
88 {
89 switch (instr->type) {
90 case nir_instr_type_alu: {
91 nir_alu_instr *alu = nir_instr_as_alu(instr);
92 if (!dest_is_invariant(&alu->dest.dest, invariants))
93 break;
94
95 alu->exact = true;
96 nir_foreach_src(instr, add_src_cb, invariants);
97 break;
98 }
99
100 case nir_instr_type_tex: {
101 nir_tex_instr *tex = nir_instr_as_tex(instr);
102 if (dest_is_invariant(&tex->dest, invariants))
103 nir_foreach_src(instr, add_src_cb, invariants);
104 break;
105 }
106
107 case nir_instr_type_intrinsic: {
108 nir_intrinsic_instr *intrin = nir_instr_as_intrinsic(instr);
109 switch (intrin->intrinsic) {
110 case nir_intrinsic_copy_deref:
111 /* If the destination is invariant then so is the source */
112 if (var_is_invariant(nir_intrinsic_get_var(intrin, 0), invariants))
113 add_var(nir_intrinsic_get_var(intrin, 1), invariants);
114 break;
115
116 case nir_intrinsic_load_deref:
117 if (dest_is_invariant(&intrin->dest, invariants))
118 add_var(nir_intrinsic_get_var(intrin, 0), invariants);
119 break;
120
121 case nir_intrinsic_store_deref:
122 if (var_is_invariant(nir_intrinsic_get_var(intrin, 0), invariants))
123 add_src(&intrin->src[1], invariants);
124 break;
125
126 default:
127 /* Nothing to do */
128 break;
129 }
130 FALLTHROUGH;
131 }
132
133 case nir_instr_type_deref:
134 case nir_instr_type_jump:
135 case nir_instr_type_ssa_undef:
136 case nir_instr_type_load_const:
137 break; /* Nothing to do */
138
139 case nir_instr_type_phi: {
140 nir_phi_instr *phi = nir_instr_as_phi(instr);
141 if (!dest_is_invariant(&phi->dest, invariants))
142 break;
143
144 nir_foreach_phi_src(src, phi) {
145 add_src(&src->src, invariants);
146 add_cf_node(&src->pred->cf_node, invariants);
147 }
148 break;
149 }
150
151 case nir_instr_type_call:
152 unreachable("This pass must be run after function inlining");
153
154 case nir_instr_type_parallel_copy:
155 default:
156 unreachable("Cannot have this instruction type");
157 }
158 }
159
160 static bool
propagate_invariant_impl(nir_function_impl * impl,struct set * invariants)161 propagate_invariant_impl(nir_function_impl *impl, struct set *invariants)
162 {
163 bool progress = false;
164
165 while (true) {
166 uint32_t prev_entries = invariants->entries;
167
168 nir_foreach_block_reverse(block, impl) {
169 nir_foreach_instr_reverse(instr, block)
170 propagate_invariant_instr(instr, invariants);
171 }
172
173 /* Keep running until we make no more progress. */
174 if (invariants->entries > prev_entries) {
175 progress = true;
176 continue;
177 } else {
178 break;
179 }
180 }
181
182 if (progress) {
183 nir_metadata_preserve(impl, nir_metadata_block_index |
184 nir_metadata_dominance |
185 nir_metadata_live_ssa_defs);
186 } else {
187 nir_metadata_preserve(impl, nir_metadata_all);
188 }
189
190 return progress;
191 }
192
193 /* If invariant_prim=true, this pass considers all geometry-affecting
194 * outputs as invariant. Doing this works around a common class of application
195 * bugs appearing as flickering.
196 */
197 bool
nir_propagate_invariant(nir_shader * shader,bool invariant_prim)198 nir_propagate_invariant(nir_shader *shader, bool invariant_prim)
199 {
200 /* Hash set of invariant things */
201 struct set *invariants = _mesa_pointer_set_create(NULL);
202
203 if (shader->info.stage != MESA_SHADER_FRAGMENT && invariant_prim) {
204 nir_foreach_shader_out_variable(var, shader) {
205 switch (var->data.location) {
206 case VARYING_SLOT_POS:
207 case VARYING_SLOT_PSIZ:
208 case VARYING_SLOT_CLIP_DIST0:
209 case VARYING_SLOT_CLIP_DIST1:
210 case VARYING_SLOT_CULL_DIST0:
211 case VARYING_SLOT_CULL_DIST1:
212 case VARYING_SLOT_TESS_LEVEL_OUTER:
213 case VARYING_SLOT_TESS_LEVEL_INNER:
214 if (!var->data.invariant)
215 _mesa_set_add(invariants, var);
216 break;
217 default:
218 break;
219 }
220 }
221 }
222
223 bool progress = false;
224 nir_foreach_function(function, shader) {
225 if (function->impl && propagate_invariant_impl(function->impl, invariants))
226 progress = true;
227 }
228
229 _mesa_set_destroy(invariants, NULL);
230
231 return progress;
232 }
233