1 /*
2 * Copyright © 2021 Valve 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 /**
25 * Lower constant arrays to uniform arrays.
26 *
27 * Some driver backends (such as i965 and nouveau) don't handle constant arrays
28 * gracefully, instead treating them as ordinary writable temporary arrays.
29 * Since arrays can be large, this often means spilling them to scratch memory,
30 * which usually involves a large number of instructions.
31 *
32 * This must be called prior to gl_nir_set_uniform_initializers(); we need the
33 * linker to process our new uniform's constant initializer.
34 *
35 * This should be called after optimizations, since those can result in
36 * splitting and removing arrays that are indexed by constant expressions.
37 */
38 #include "nir.h"
39 #include "nir_builder.h"
40 #include "nir_deref.h"
41
42 struct var_info {
43 nir_variable *var;
44
45 bool is_constant;
46 bool found_read;
47
48 /* Block that has all the variable stores. All the blocks with reads
49 * should be dominated by this block.
50 */
51 nir_block *block;
52 };
53
54 static void
set_const_initialiser(nir_deref_instr ** p,nir_constant * top_level_init,nir_src * const_src,unsigned writemask)55 set_const_initialiser(nir_deref_instr **p, nir_constant *top_level_init,
56 nir_src *const_src, unsigned writemask)
57 {
58 assert(*p);
59
60 nir_constant *ret = top_level_init;
61 for ( ; *p; p++) {
62 if ((*p)->deref_type == nir_deref_type_array) {
63 assert(nir_src_is_const((*p)->arr.index));
64
65 uint64_t idx = nir_src_as_uint((*p)->arr.index);
66
67 /* Just return if this is an out of bounds write */
68 if (idx >= ret->num_elements)
69 return;
70
71 ret = ret->elements[idx];
72 } else if ((*p)->deref_type == nir_deref_type_struct) {
73 ret = ret->elements[(*p)->strct.index];
74 } else {
75 unreachable("Unsupported deref type");
76 }
77 }
78
79 /* Now that we have selected the corrent nir_constant we copy the constant
80 * values to it.
81 */
82 assert(const_src->is_ssa);
83 nir_instr *src_instr = const_src->ssa->parent_instr;
84 assert(src_instr->type == nir_instr_type_load_const);
85 nir_load_const_instr* load = nir_instr_as_load_const(src_instr);
86
87 for (unsigned i = 0; i < load->def.num_components; i++) {
88 if (!(writemask & (1 << i)))
89 continue;
90
91 memcpy(ret->values + i, load->value + i, sizeof(*load->value));
92 }
93
94 return;
95 }
96
97 static nir_constant *
rebuild_const_array_initialiser(const struct glsl_type * type,void * mem_ctx)98 rebuild_const_array_initialiser(const struct glsl_type *type, void *mem_ctx)
99 {
100 nir_constant *ret = rzalloc(mem_ctx, nir_constant);
101
102 if (glsl_type_is_matrix(type) && glsl_get_matrix_columns(type) > 1) {
103 ret->num_elements = glsl_get_matrix_columns(type);
104 ret->elements = ralloc_array(mem_ctx, nir_constant *, ret->num_elements);
105
106 for (unsigned i = 0; i < ret->num_elements; i++) {
107 ret->elements[i] = rzalloc(mem_ctx, nir_constant);
108 }
109
110 return ret;
111 }
112
113 if (glsl_type_is_array(type) || glsl_type_is_struct(type)) {
114 ret->num_elements = glsl_get_length(type);
115 ret->elements = ralloc_array(mem_ctx, nir_constant *, ret->num_elements);
116
117 for (unsigned i = 0; i < ret->num_elements; i++) {
118 if (glsl_type_is_array(type)) {
119 ret->elements[i] =
120 rebuild_const_array_initialiser(glsl_get_array_element(type), mem_ctx);
121 } else {
122 ret->elements[i] =
123 rebuild_const_array_initialiser(glsl_get_struct_field(type, i), mem_ctx);
124 }
125 }
126 }
127
128 return ret;
129 }
130
131 static bool
lower_const_array_to_uniform(nir_shader * shader,struct var_info * info,struct hash_table * const_array_vars,unsigned * free_uni_components,unsigned * const_count,bool * progress)132 lower_const_array_to_uniform(nir_shader *shader, struct var_info *info,
133 struct hash_table *const_array_vars,
134 unsigned *free_uni_components,
135 unsigned *const_count, bool *progress)
136 {
137 nir_variable *var = info->var;
138
139 if (!info->is_constant)
140 return true;
141
142 if (!glsl_type_is_array(var->type))
143 return true;
144
145 /* TODO: Add support for 8bit and 16bit types */
146 if (!glsl_type_is_32bit(glsl_without_array(var->type)) &&
147 !glsl_type_is_64bit(glsl_without_array(var->type)))
148 return true;
149
150 /* How many uniform component slots are required? */
151 unsigned component_slots = glsl_get_component_slots(var->type);
152
153 /* We would utilize more than is available, bail out. */
154 if (component_slots > *free_uni_components)
155 return false;
156
157 *free_uni_components -= component_slots;
158
159 /* In the very unlikely event of 4294967295 constant arrays in a single
160 * shader, don't promote this to a uniform.
161 */
162 unsigned limit = ~0;
163 if (*const_count == limit)
164 return false;
165
166 nir_variable *uni = rzalloc(shader, nir_variable);
167
168 /* Rebuild constant initialiser */
169 nir_constant *const_init = rebuild_const_array_initialiser(var->type, uni);
170
171 /* Set constant initialiser */
172 nir_function_impl *impl = nir_shader_get_entrypoint(shader);
173 nir_foreach_block(block, impl) {
174 nir_foreach_instr(instr, block) {
175 if (instr->type != nir_instr_type_intrinsic)
176 continue;
177
178 nir_intrinsic_instr *intrin = nir_instr_as_intrinsic(instr);
179 assert(intrin->intrinsic != nir_intrinsic_copy_deref);
180 if (intrin->intrinsic != nir_intrinsic_store_deref)
181 continue;
182
183 nir_deref_instr *deref = nir_src_as_deref(intrin->src[0]);
184 nir_variable *deref_var = nir_deref_instr_get_variable(deref);
185 if (var != deref_var)
186 continue;
187
188 nir_deref_path path;
189 nir_deref_path_init(&path, deref, NULL);
190 assert(path.path[0]->deref_type == nir_deref_type_var);
191
192 nir_deref_instr **p = &path.path[1];
193 set_const_initialiser(p, const_init, &intrin->src[1],
194 nir_intrinsic_write_mask(intrin));
195
196 nir_deref_path_finish(&path);
197 }
198 }
199
200 uni->constant_initializer = const_init;
201 uni->data.how_declared = nir_var_hidden;
202 uni->data.read_only = true;
203 uni->data.mode = nir_var_uniform;
204 uni->type = info->var->type;
205 uni->name = ralloc_asprintf(uni, "constarray_%x_%u",
206 *const_count, shader->info.stage);
207
208 nir_shader_add_variable(shader, uni);
209
210 *const_count = *const_count + 1;
211
212 _mesa_hash_table_insert(const_array_vars, info->var, uni);
213
214 *progress = true;
215
216 return true;
217 }
218
219 static unsigned
count_uniforms(nir_shader * shader)220 count_uniforms(nir_shader *shader)
221 {
222 unsigned total = 0;
223
224 nir_foreach_variable_with_modes(var, shader, nir_var_uniform) {
225 total += glsl_get_component_slots(var->type);
226 }
227
228 return total;
229 }
230
231 bool
nir_lower_const_arrays_to_uniforms(nir_shader * shader,unsigned max_uniform_components)232 nir_lower_const_arrays_to_uniforms(nir_shader *shader,
233 unsigned max_uniform_components)
234 {
235 /* This only works with a single entrypoint */
236 nir_function_impl *impl = nir_shader_get_entrypoint(shader);
237
238 unsigned num_locals = nir_function_impl_index_vars(impl);
239 if (num_locals == 0) {
240 nir_shader_preserve_all_metadata(shader);
241 return false;
242 }
243
244 bool progress = false;
245 unsigned uniform_components = count_uniforms(shader);
246 unsigned free_uni_components = max_uniform_components - uniform_components;
247 unsigned const_count = 0;
248
249 struct var_info *var_infos = ralloc_array(NULL, struct var_info, num_locals);
250 nir_foreach_function_temp_variable(var, impl) {
251 var_infos[var->index] = (struct var_info) {
252 .var = var,
253 .is_constant = true,
254 .found_read = false,
255 };
256 }
257
258 nir_metadata_require(impl, nir_metadata_dominance);
259
260 struct hash_table *const_array_vars =
261 _mesa_hash_table_create(NULL, _mesa_hash_pointer, _mesa_key_pointer_equal);
262
263 /* First, walk through the shader and figure out what variables we can
264 * lower to a uniform.
265 */
266 nir_foreach_block(block, impl) {
267 nir_foreach_instr(instr, block) {
268 if (instr->type == nir_instr_type_deref) {
269 /* If we ever see a complex use of a deref_var, we have to assume
270 * that variable is non-constant because we can't guarantee we
271 * will find all of the writers of that variable.
272 */
273 nir_deref_instr *deref = nir_instr_as_deref(instr);
274 if (deref->deref_type == nir_deref_type_var &&
275 deref->var->data.mode == nir_var_function_temp &&
276 nir_deref_instr_has_complex_use(deref, 0))
277 var_infos[deref->var->index].is_constant = false;
278 continue;
279 }
280
281 if (instr->type != nir_instr_type_intrinsic)
282 continue;
283
284 nir_intrinsic_instr *intrin = nir_instr_as_intrinsic(instr);
285
286 bool src_is_const = false;
287 nir_deref_instr *src_deref = NULL, *dst_deref = NULL;
288 switch (intrin->intrinsic) {
289 case nir_intrinsic_store_deref:
290 dst_deref = nir_src_as_deref(intrin->src[0]);
291 src_is_const = nir_src_is_const(intrin->src[1]);
292 break;
293
294 case nir_intrinsic_load_deref:
295 src_deref = nir_src_as_deref(intrin->src[0]);
296 break;
297
298 case nir_intrinsic_copy_deref:
299 assert(!"Lowering of copy_deref with const arrays to uniform is prohibited");
300 break;
301
302 default:
303 continue;
304 }
305
306 if (dst_deref && nir_deref_mode_must_be(dst_deref, nir_var_function_temp)) {
307 nir_variable *var = nir_deref_instr_get_variable(dst_deref);
308 if (var == NULL)
309 continue;
310
311 assert(var->data.mode == nir_var_function_temp);
312
313 struct var_info *info = &var_infos[var->index];
314 if (!info->is_constant)
315 continue;
316
317 if (!info->block)
318 info->block = block;
319
320 /* We only consider variables constant if they only have constant
321 * stores, all the stores come before any reads, and all stores
322 * come from the same block. We also can't handle indirect stores.
323 */
324 if (!src_is_const || info->found_read || block != info->block ||
325 nir_deref_instr_has_indirect(dst_deref)) {
326 info->is_constant = false;
327 }
328 }
329
330 if (src_deref && nir_deref_mode_must_be(src_deref, nir_var_function_temp)) {
331 nir_variable *var = nir_deref_instr_get_variable(src_deref);
332 if (var == NULL)
333 continue;
334
335 assert(var->data.mode == nir_var_function_temp);
336
337 /* We only consider variables constant if all the reads are
338 * dominated by the block that writes to it.
339 */
340 struct var_info *info = &var_infos[var->index];
341 if (!info->is_constant)
342 continue;
343
344 if (!info->block || !nir_block_dominates(info->block, block))
345 info->is_constant = false;
346
347 info->found_read = true;
348 }
349 }
350 }
351
352 /* Now lower the constants to uniforms */
353 for (int i = 0; i < num_locals; i++) {
354 struct var_info *info = &var_infos[i];
355 if (!lower_const_array_to_uniform(shader, info, const_array_vars,
356 &free_uni_components, &const_count,
357 &progress))
358 break;
359 }
360
361 /* Finally rewrite its uses */
362 nir_builder b;
363 nir_builder_init(&b, impl);
364 nir_foreach_block(block, impl) {
365 nir_foreach_instr_safe(instr, block) {
366
367 if (instr->type != nir_instr_type_intrinsic)
368 continue;
369
370 nir_intrinsic_instr *intrin = nir_instr_as_intrinsic(instr);
371 if (intrin->intrinsic != nir_intrinsic_load_deref)
372 continue;
373
374 nir_deref_instr *deref = nir_src_as_deref(intrin->src[0]);
375 nir_variable *var = nir_deref_instr_get_variable(deref);
376
377 struct hash_entry *entry =
378 _mesa_hash_table_search(const_array_vars, var);
379 if (!entry)
380 continue;
381
382 b.cursor = nir_before_instr(instr);
383
384 nir_variable *uni = (nir_variable *) entry->data;
385 nir_deref_instr *new_deref_instr = nir_build_deref_var(&b, uni);
386
387 nir_deref_path path;
388 nir_deref_path_init(&path, deref, NULL);
389 assert(path.path[0]->deref_type == nir_deref_type_var);
390
391 nir_deref_instr **p = &path.path[1];
392 for (; *p; p++) {
393 if ((*p)->deref_type == nir_deref_type_array) {
394 new_deref_instr = nir_build_deref_array(&b, new_deref_instr,
395 (*p)->arr.index.ssa);
396 } else if ((*p)->deref_type == nir_deref_type_struct) {
397 new_deref_instr = nir_build_deref_struct(&b, new_deref_instr,
398 (*p)->strct.index);
399 } else {
400 unreachable("Unsupported deref type");
401 }
402 }
403 nir_deref_path_finish(&path);
404
405 nir_ssa_def *new_def = nir_load_deref(&b, new_deref_instr);
406
407 nir_ssa_def_rewrite_uses(&intrin->dest.ssa, new_def);
408 nir_instr_remove(&intrin->instr);
409 }
410 }
411
412 nir_metadata_preserve(impl, nir_metadata_block_index |
413 nir_metadata_dominance);
414
415 ralloc_free(var_infos);
416 _mesa_hash_table_destroy(const_array_vars, NULL);
417
418 return progress;
419 }
420