1 /*
2 * Copyright (c) 2019 Zodiac Inflight Innovations
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, sub license,
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
12 * next paragraph) shall be included in all copies or substantial portions
13 * of the 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 NON-INFRINGEMENT. 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 * Authors:
24 * Jonathan Marek <jonathan@marek.ca>
25 */
26
27 #include "etnaviv_compiler_nir.h"
28 #include "compiler/nir/nir_worklist.h"
29
30 static void
range_include(struct live_def * def,unsigned index)31 range_include(struct live_def *def, unsigned index)
32 {
33 if (def->live_start > index)
34 def->live_start = index;
35 if (def->live_end < index)
36 def->live_end = index;
37 }
38
39 struct live_defs_state {
40 unsigned num_defs;
41 unsigned bitset_words;
42
43 nir_function_impl *impl;
44 nir_block *block; /* current block pointer */
45 unsigned index; /* current live index */
46
47 struct live_def *defs;
48 unsigned *live_map; /* to map ssa/reg index into defs array */
49
50 nir_block_worklist worklist;
51 };
52
53 static bool
init_liveness_block(nir_block * block,struct live_defs_state * state)54 init_liveness_block(nir_block *block,
55 struct live_defs_state *state)
56 {
57 block->live_in = reralloc(block, block->live_in, BITSET_WORD,
58 state->bitset_words);
59 memset(block->live_in, 0, state->bitset_words * sizeof(BITSET_WORD));
60
61 block->live_out = reralloc(block, block->live_out, BITSET_WORD,
62 state->bitset_words);
63 memset(block->live_out, 0, state->bitset_words * sizeof(BITSET_WORD));
64
65 nir_block_worklist_push_head(&state->worklist, block);
66
67 return true;
68 }
69
70 static bool
set_src_live(nir_src * src,void * void_state)71 set_src_live(nir_src *src, void *void_state)
72 {
73 struct live_defs_state *state = void_state;
74
75 nir_instr *instr = src->ssa->parent_instr;
76
77 if (is_sysval(instr) || instr->type == nir_instr_type_deref)
78 return true;
79
80 switch (instr->type) {
81 case nir_instr_type_load_const:
82 case nir_instr_type_undef:
83 return true;
84 case nir_instr_type_alu: {
85 /* alu op bypass */
86 nir_alu_instr *alu = nir_instr_as_alu(instr);
87 if (instr->pass_flags & BYPASS_SRC) {
88 for (unsigned i = 0; i < nir_op_infos[alu->op].num_inputs; i++)
89 set_src_live(&alu->src[i].src, state);
90 return true;
91 }
92 break;
93 }
94 default:
95 break;
96 }
97
98 unsigned i = state->live_map[src_index(state->impl, src)];
99 assert(i != ~0u);
100
101 BITSET_SET(state->block->live_in, i);
102 range_include(&state->defs[i], state->index);
103
104 return true;
105 }
106
107 static bool
propagate_across_edge(nir_block * pred,nir_block * succ,struct live_defs_state * state)108 propagate_across_edge(nir_block *pred, nir_block *succ,
109 struct live_defs_state *state)
110 {
111 BITSET_WORD progress = 0;
112 for (unsigned i = 0; i < state->bitset_words; ++i) {
113 progress |= succ->live_in[i] & ~pred->live_out[i];
114 pred->live_out[i] |= succ->live_in[i];
115 }
116 return progress != 0;
117 }
118
119 unsigned
etna_live_defs(nir_function_impl * impl,struct live_def * defs,unsigned * live_map)120 etna_live_defs(nir_function_impl *impl, struct live_def *defs, unsigned *live_map)
121 {
122 struct live_defs_state state;
123 unsigned block_live_index[impl->num_blocks + 1];
124
125 state.impl = impl;
126 state.defs = defs;
127 state.live_map = live_map;
128
129 state.num_defs = 0;
130 nir_foreach_block(block, impl) {
131 block_live_index[block->index] = state.num_defs;
132 nir_foreach_instr(instr, block) {
133 nir_def *def = def_for_instr(instr);
134 if (!def)
135 continue;
136
137 unsigned idx = def_index(impl, def);
138 /* register is already in defs */
139 if (live_map[idx] != ~0u)
140 continue;
141
142 defs[state.num_defs] = (struct live_def) {instr, def, state.num_defs, 0};
143
144 /* input live from the start */
145 if (instr->type == nir_instr_type_intrinsic) {
146 nir_intrinsic_instr *intr = nir_instr_as_intrinsic(instr);
147 if (intr->intrinsic == nir_intrinsic_load_input ||
148 intr->intrinsic == nir_intrinsic_load_instance_id)
149 defs[state.num_defs].live_start = 0;
150 }
151
152 live_map[idx] = state.num_defs;
153 state.num_defs++;
154 }
155 }
156 block_live_index[impl->num_blocks] = state.num_defs;
157
158 nir_block_worklist_init(&state.worklist, impl->num_blocks, NULL);
159
160 /* We now know how many unique ssa definitions we have and we can go
161 * ahead and allocate live_in and live_out sets and add all of the
162 * blocks to the worklist.
163 */
164 state.bitset_words = BITSET_WORDS(state.num_defs);
165 nir_foreach_block(block, impl) {
166 init_liveness_block(block, &state);
167 }
168
169 /* We're now ready to work through the worklist and update the liveness
170 * sets of each of the blocks. By the time we get to this point, every
171 * block in the function implementation has been pushed onto the
172 * worklist in reverse order. As long as we keep the worklist
173 * up-to-date as we go, everything will get covered.
174 */
175 while (!nir_block_worklist_is_empty(&state.worklist)) {
176 /* We pop them off in the reverse order we pushed them on. This way
177 * the first walk of the instructions is backwards so we only walk
178 * once in the case of no control flow.
179 */
180 nir_block *block = nir_block_worklist_pop_head(&state.worklist);
181 state.block = block;
182
183 memcpy(block->live_in, block->live_out,
184 state.bitset_words * sizeof(BITSET_WORD));
185
186 state.index = block_live_index[block->index + 1];
187
188 nir_if *following_if = nir_block_get_following_if(block);
189 if (following_if)
190 set_src_live(&following_if->condition, &state);
191
192 nir_foreach_instr_reverse(instr, block) {
193 /* when we come across the next "live" instruction, decrement index */
194 if (state.index && instr == defs[state.index - 1].instr) {
195 state.index--;
196 /* the only source of writes to registers is phis:
197 * we don't expect any partial write_mask alus
198 * so clearing live_in here is OK
199 */
200 BITSET_CLEAR(block->live_in, state.index);
201 }
202
203 /* don't set_src_live for not-emitted instructions */
204 if (is_dead_instruction(instr))
205 continue;
206
207 unsigned index = state.index;
208
209 /* output live till the end */
210 if (instr->type == nir_instr_type_intrinsic) {
211 nir_intrinsic_instr *intr = nir_instr_as_intrinsic(instr);
212 if (intr->intrinsic == nir_intrinsic_store_deref)
213 state.index = ~0u;
214 }
215
216 bool processed = false;
217
218 if (instr->type == nir_instr_type_intrinsic) {
219 nir_intrinsic_instr *intr = nir_instr_as_intrinsic(instr);
220 if (intr->intrinsic == nir_intrinsic_decl_reg ||
221 intr->intrinsic == nir_intrinsic_store_reg)
222 processed = true;
223 }
224
225 if (!processed)
226 nir_foreach_src(instr, set_src_live, &state);
227
228 state.index = index;
229 }
230 assert(state.index == block_live_index[block->index]);
231
232 /* Walk over all of the predecessors of the current block updating
233 * their live in with the live out of this one. If anything has
234 * changed, add the predecessor to the work list so that we ensure
235 * that the new information is used.
236 */
237 set_foreach(block->predecessors, entry) {
238 nir_block *pred = (nir_block *)entry->key;
239 if (propagate_across_edge(pred, block, &state))
240 nir_block_worklist_push_tail(&state.worklist, pred);
241 }
242 }
243
244 nir_block_worklist_fini(&state.worklist);
245
246 /* apply live_in/live_out to ranges */
247
248 nir_foreach_block(block, impl) {
249 int i;
250
251 BITSET_FOREACH_SET(i, block->live_in, state.num_defs)
252 range_include(&state.defs[i], block_live_index[block->index]);
253
254 BITSET_FOREACH_SET(i, block->live_out, state.num_defs)
255 range_include(&state.defs[i], block_live_index[block->index + 1]);
256 }
257
258 return state.num_defs;
259 }
260