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 if (src->is_ssa) {
76 nir_instr *instr = src->ssa->parent_instr;
77
78 if (is_sysval(instr) || instr->type == nir_instr_type_deref)
79 return true;
80
81 switch (instr->type) {
82 case nir_instr_type_load_const:
83 case nir_instr_type_ssa_undef:
84 return true;
85 case nir_instr_type_alu: {
86 /* alu op bypass */
87 nir_alu_instr *alu = nir_instr_as_alu(instr);
88 if (instr->pass_flags & BYPASS_SRC) {
89 for (unsigned i = 0; i < nir_op_infos[alu->op].num_inputs; i++)
90 set_src_live(&alu->src[i].src, state);
91 return true;
92 }
93 } break;
94 default:
95 break;
96 }
97 }
98
99 unsigned i = state->live_map[src_index(state->impl, src)];
100 assert(i != ~0u);
101
102 BITSET_SET(state->block->live_in, i);
103 range_include(&state->defs[i], state->index);
104
105 return true;
106 }
107
108 static bool
propagate_across_edge(nir_block * pred,nir_block * succ,struct live_defs_state * state)109 propagate_across_edge(nir_block *pred, nir_block *succ,
110 struct live_defs_state *state)
111 {
112 BITSET_WORD progress = 0;
113 for (unsigned i = 0; i < state->bitset_words; ++i) {
114 progress |= succ->live_in[i] & ~pred->live_out[i];
115 pred->live_out[i] |= succ->live_in[i];
116 }
117 return progress != 0;
118 }
119
120 unsigned
etna_live_defs(nir_function_impl * impl,struct live_def * defs,unsigned * live_map)121 etna_live_defs(nir_function_impl *impl, struct live_def *defs, unsigned *live_map)
122 {
123 struct live_defs_state state;
124 unsigned block_live_index[impl->num_blocks + 1];
125
126 state.impl = impl;
127 state.defs = defs;
128 state.live_map = live_map;
129
130 state.num_defs = 0;
131 nir_foreach_block(block, impl) {
132 block_live_index[block->index] = state.num_defs;
133 nir_foreach_instr(instr, block) {
134 nir_dest *dest = dest_for_instr(instr);
135 if (!dest)
136 continue;
137
138 unsigned idx = dest_index(impl, dest);
139 /* register is already in defs */
140 if (live_map[idx] != ~0u)
141 continue;
142
143 defs[state.num_defs] = (struct live_def) {instr, dest, state.num_defs, 0};
144
145 /* input live from the start */
146 if (instr->type == nir_instr_type_intrinsic) {
147 nir_intrinsic_instr *intr = nir_instr_as_intrinsic(instr);
148 if (intr->intrinsic == nir_intrinsic_load_input ||
149 intr->intrinsic == nir_intrinsic_load_instance_id)
150 defs[state.num_defs].live_start = 0;
151 }
152
153 live_map[idx] = state.num_defs;
154 state.num_defs++;
155 }
156 }
157 block_live_index[impl->num_blocks] = state.num_defs;
158
159 nir_block_worklist_init(&state.worklist, impl->num_blocks, NULL);
160
161 /* We now know how many unique ssa definitions we have and we can go
162 * ahead and allocate live_in and live_out sets and add all of the
163 * blocks to the worklist.
164 */
165 state.bitset_words = BITSET_WORDS(state.num_defs);
166 nir_foreach_block(block, impl) {
167 init_liveness_block(block, &state);
168 }
169
170 /* We're now ready to work through the worklist and update the liveness
171 * sets of each of the blocks. By the time we get to this point, every
172 * block in the function implementation has been pushed onto the
173 * worklist in reverse order. As long as we keep the worklist
174 * up-to-date as we go, everything will get covered.
175 */
176 while (!nir_block_worklist_is_empty(&state.worklist)) {
177 /* We pop them off in the reverse order we pushed them on. This way
178 * the first walk of the instructions is backwards so we only walk
179 * once in the case of no control flow.
180 */
181 nir_block *block = nir_block_worklist_pop_head(&state.worklist);
182 state.block = block;
183
184 memcpy(block->live_in, block->live_out,
185 state.bitset_words * sizeof(BITSET_WORD));
186
187 state.index = block_live_index[block->index + 1];
188
189 nir_if *following_if = nir_block_get_following_if(block);
190 if (following_if)
191 set_src_live(&following_if->condition, &state);
192
193 nir_foreach_instr_reverse(instr, block) {
194 /* when we come across the next "live" instruction, decrement index */
195 if (state.index && instr == defs[state.index - 1].instr) {
196 state.index--;
197 /* the only source of writes to registers is phis:
198 * we don't expect any partial write_mask alus
199 * so clearing live_in here is OK
200 */
201 BITSET_CLEAR(block->live_in, state.index);
202 }
203
204 /* don't set_src_live for not-emitted instructions */
205 if (instr->pass_flags)
206 continue;
207
208 unsigned index = state.index;
209
210 /* output live till the end */
211 if (instr->type == nir_instr_type_intrinsic) {
212 nir_intrinsic_instr *intr = nir_instr_as_intrinsic(instr);
213 if (intr->intrinsic == nir_intrinsic_store_deref)
214 state.index = ~0u;
215 }
216
217 nir_foreach_src(instr, set_src_live, &state);
218
219 state.index = index;
220 }
221 assert(state.index == block_live_index[block->index]);
222
223 /* Walk over all of the predecessors of the current block updating
224 * their live in with the live out of this one. If anything has
225 * changed, add the predecessor to the work list so that we ensure
226 * that the new information is used.
227 */
228 set_foreach(block->predecessors, entry) {
229 nir_block *pred = (nir_block *)entry->key;
230 if (propagate_across_edge(pred, block, &state))
231 nir_block_worklist_push_tail(&state.worklist, pred);
232 }
233 }
234
235 nir_block_worklist_fini(&state.worklist);
236
237 /* apply live_in/live_out to ranges */
238
239 nir_foreach_block(block, impl) {
240 int i;
241
242 BITSET_FOREACH_SET(i, block->live_in, state.num_defs)
243 range_include(&state.defs[i], block_live_index[block->index]);
244
245 BITSET_FOREACH_SET(i, block->live_out, state.num_defs)
246 range_include(&state.defs[i], block_live_index[block->index + 1]);
247 }
248
249 return state.num_defs;
250 }
251