1 /*
2 * Copyright © 2018 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
24 #include "nir.h"
25 #include "nir_builder.h"
26 #include "nir_deref.h"
27
28 struct var_info {
29 nir_variable *var;
30
31 bool is_constant;
32 bool found_read;
33 bool duplicate;
34
35 /* Block that has all the variable stores. All the blocks with reads
36 * should be dominated by this block.
37 */
38 nir_block *block;
39
40 /* If is_constant, hold the collected constant data for this var. */
41 uint32_t constant_data_size;
42 void *constant_data;
43 };
44
45 static int
var_info_cmp(const void * _a,const void * _b)46 var_info_cmp(const void *_a, const void *_b)
47 {
48 const struct var_info *a = _a;
49 const struct var_info *b = _b;
50 uint32_t a_size = a->constant_data_size;
51 uint32_t b_size = b->constant_data_size;
52
53 if (a->is_constant != b->is_constant) {
54 return (int)a->is_constant - (int)b->is_constant;
55 } else if (a_size < b_size) {
56 return -1;
57 } else if (a_size > b_size) {
58 return 1;
59 } else if (a_size == 0) {
60 /* Don't call memcmp with invalid pointers. */
61 return 0;
62 } else {
63 return memcmp(a->constant_data, b->constant_data, a_size);
64 }
65 }
66
67 static nir_ssa_def *
build_constant_load(nir_builder * b,nir_deref_instr * deref,glsl_type_size_align_func size_align)68 build_constant_load(nir_builder *b, nir_deref_instr *deref,
69 glsl_type_size_align_func size_align)
70 {
71 nir_variable *var = nir_deref_instr_get_variable(deref);
72
73 const unsigned bit_size = glsl_get_bit_size(deref->type);
74 const unsigned num_components = glsl_get_vector_elements(deref->type);
75
76 UNUSED unsigned var_size, var_align;
77 size_align(var->type, &var_size, &var_align);
78 assert(var->data.location % var_align == 0);
79
80 UNUSED unsigned deref_size, deref_align;
81 size_align(deref->type, &deref_size, &deref_align);
82
83 nir_ssa_def *src = nir_build_deref_offset(b, deref, size_align);
84 nir_ssa_def *load =
85 nir_load_constant(b, num_components, bit_size, src,
86 .base = var->data.location,
87 .range = var_size,
88 .align_mul = deref_align,
89 .align_offset = 0);
90
91 if (load->bit_size < 8) {
92 /* Booleans are special-cased to be 32-bit */
93 assert(glsl_type_is_boolean(deref->type));
94 assert(deref_size == num_components * 4);
95 load->bit_size = 32;
96 return nir_b2b1(b, load);
97 } else {
98 assert(deref_size == num_components * bit_size / 8);
99 return load;
100 }
101 }
102
103 static void
handle_constant_store(void * mem_ctx,struct var_info * info,nir_deref_instr * deref,nir_const_value * val,unsigned writemask,glsl_type_size_align_func size_align)104 handle_constant_store(void *mem_ctx, struct var_info *info,
105 nir_deref_instr *deref, nir_const_value *val,
106 unsigned writemask,
107 glsl_type_size_align_func size_align)
108 {
109 assert(!nir_deref_instr_has_indirect(deref));
110 const unsigned bit_size = glsl_get_bit_size(deref->type);
111 const unsigned num_components = glsl_get_vector_elements(deref->type);
112
113 if (info->constant_data_size == 0) {
114 unsigned var_size, var_align;
115 size_align(info->var->type, &var_size, &var_align);
116 info->constant_data_size = var_size;
117 info->constant_data = rzalloc_size(mem_ctx, var_size);
118 }
119
120 const unsigned offset = nir_deref_instr_get_const_offset(deref, size_align);
121 if (offset >= info->constant_data_size)
122 return;
123
124 char *dst = (char *)info->constant_data + offset;
125
126 for (unsigned i = 0; i < num_components; i++) {
127 if (!(writemask & (1 << i)))
128 continue;
129
130 switch (bit_size) {
131 case 1:
132 /* Booleans are special-cased to be 32-bit */
133 ((int32_t *)dst)[i] = -(int)val[i].b;
134 break;
135
136 case 8:
137 ((uint8_t *)dst)[i] = val[i].u8;
138 break;
139
140 case 16:
141 ((uint16_t *)dst)[i] = val[i].u16;
142 break;
143
144 case 32:
145 ((uint32_t *)dst)[i] = val[i].u32;
146 break;
147
148 case 64:
149 ((uint64_t *)dst)[i] = val[i].u64;
150 break;
151
152 default:
153 unreachable("Invalid bit size");
154 }
155 }
156 }
157
158 /** Lower large constant variables to shader constant data
159 *
160 * This pass looks for large (type_size(var->type) > threshold) variables
161 * which are statically constant and moves them into shader constant data.
162 * This is especially useful when large tables are baked into the shader
163 * source code because they can be moved into a UBO by the driver to reduce
164 * register pressure and make indirect access cheaper.
165 */
166 bool
nir_opt_large_constants(nir_shader * shader,glsl_type_size_align_func size_align,unsigned threshold)167 nir_opt_large_constants(nir_shader *shader,
168 glsl_type_size_align_func size_align,
169 unsigned threshold)
170 {
171 /* Default to a natural alignment if none is provided */
172 if (size_align == NULL)
173 size_align = glsl_get_natural_size_align_bytes;
174
175 /* This only works with a single entrypoint */
176 nir_function_impl *impl = nir_shader_get_entrypoint(shader);
177
178 unsigned num_locals = nir_function_impl_index_vars(impl);
179
180 if (num_locals == 0) {
181 nir_shader_preserve_all_metadata(shader);
182 return false;
183 }
184
185 struct var_info *var_infos = ralloc_array(NULL, struct var_info, num_locals);
186 nir_foreach_function_temp_variable(var, impl) {
187 var_infos[var->index] = (struct var_info) {
188 .var = var,
189 .is_constant = true,
190 .found_read = false,
191 };
192 }
193
194 nir_metadata_require(impl, nir_metadata_dominance);
195
196 /* First, walk through the shader and figure out what variables we can
197 * lower to the constant blob.
198 */
199 nir_foreach_block(block, impl) {
200 nir_foreach_instr(instr, block) {
201 if (instr->type == nir_instr_type_deref) {
202 /* If we ever see a complex use of a deref_var, we have to assume
203 * that variable is non-constant because we can't guarantee we
204 * will find all of the writers of that variable.
205 */
206 nir_deref_instr *deref = nir_instr_as_deref(instr);
207 if (deref->deref_type == nir_deref_type_var &&
208 deref->var->data.mode == nir_var_function_temp &&
209 nir_deref_instr_has_complex_use(deref))
210 var_infos[deref->var->index].is_constant = false;
211 continue;
212 }
213
214 if (instr->type != nir_instr_type_intrinsic)
215 continue;
216
217 nir_intrinsic_instr *intrin = nir_instr_as_intrinsic(instr);
218
219 bool src_is_const = false;
220 nir_deref_instr *src_deref = NULL, *dst_deref = NULL;
221 unsigned writemask = 0;
222 switch (intrin->intrinsic) {
223 case nir_intrinsic_store_deref:
224 dst_deref = nir_src_as_deref(intrin->src[0]);
225 src_is_const = nir_src_is_const(intrin->src[1]);
226 writemask = nir_intrinsic_write_mask(intrin);
227 break;
228
229 case nir_intrinsic_load_deref:
230 src_deref = nir_src_as_deref(intrin->src[0]);
231 break;
232
233 case nir_intrinsic_copy_deref:
234 assert(!"Lowering of copy_deref with large constants is prohibited");
235 break;
236
237 default:
238 continue;
239 }
240
241 if (dst_deref && nir_deref_mode_must_be(dst_deref, nir_var_function_temp)) {
242 nir_variable *var = nir_deref_instr_get_variable(dst_deref);
243 if (var == NULL)
244 continue;
245
246 assert(var->data.mode == nir_var_function_temp);
247
248 struct var_info *info = &var_infos[var->index];
249 if (!info->is_constant)
250 continue;
251
252 if (!info->block)
253 info->block = block;
254
255 /* We only consider variables constant if they only have constant
256 * stores, all the stores come before any reads, and all stores
257 * come from the same block. We also can't handle indirect stores.
258 */
259 if (!src_is_const || info->found_read || block != info->block ||
260 nir_deref_instr_has_indirect(dst_deref)) {
261 info->is_constant = false;
262 } else {
263 nir_const_value *val = nir_src_as_const_value(intrin->src[1]);
264 handle_constant_store(var_infos, info, dst_deref, val, writemask,
265 size_align);
266 }
267 }
268
269 if (src_deref && nir_deref_mode_must_be(src_deref, nir_var_function_temp)) {
270 nir_variable *var = nir_deref_instr_get_variable(src_deref);
271 if (var == NULL)
272 continue;
273
274 assert(var->data.mode == nir_var_function_temp);
275
276 /* We only consider variables constant if all the reads are
277 * dominated by the block that writes to it.
278 */
279 struct var_info *info = &var_infos[var->index];
280 if (!info->is_constant)
281 continue;
282
283 if (!info->block || !nir_block_dominates(info->block, block))
284 info->is_constant = false;
285
286 info->found_read = true;
287 }
288 }
289 }
290
291 /* Allocate constant data space for each variable that just has constant
292 * data. We sort them by size and content so we can easily find
293 * duplicates.
294 */
295 const unsigned old_constant_data_size = shader->constant_data_size;
296 qsort(var_infos, num_locals, sizeof(struct var_info), var_info_cmp);
297 for (int i = 0; i < num_locals; i++) {
298 struct var_info *info = &var_infos[i];
299
300 /* Fix up indices after we sorted. */
301 info->var->index = i;
302
303 if (!info->is_constant)
304 continue;
305
306 unsigned var_size, var_align;
307 size_align(info->var->type, &var_size, &var_align);
308 if (var_size <= threshold || !info->found_read) {
309 /* Don't bother lowering small stuff or data that's never read */
310 info->is_constant = false;
311 continue;
312 }
313
314 if (i > 0 && var_info_cmp(info, &var_infos[i - 1]) == 0) {
315 info->var->data.location = var_infos[i - 1].var->data.location;
316 info->duplicate = true;
317 } else {
318 info->var->data.location = ALIGN_POT(shader->constant_data_size, var_align);
319 shader->constant_data_size = info->var->data.location + var_size;
320 }
321 }
322
323 if (shader->constant_data_size == old_constant_data_size) {
324 nir_shader_preserve_all_metadata(shader);
325 ralloc_free(var_infos);
326 return false;
327 }
328
329 assert(shader->constant_data_size > old_constant_data_size);
330 shader->constant_data = rerzalloc_size(shader, shader->constant_data,
331 old_constant_data_size,
332 shader->constant_data_size);
333 for (int i = 0; i < num_locals; i++) {
334 struct var_info *info = &var_infos[i];
335 if (!info->duplicate && info->is_constant) {
336 memcpy((char *)shader->constant_data + info->var->data.location,
337 info->constant_data, info->constant_data_size);
338 }
339 }
340
341 nir_builder b;
342 nir_builder_init(&b, impl);
343
344 nir_foreach_block(block, impl) {
345 nir_foreach_instr_safe(instr, block) {
346 if (instr->type != nir_instr_type_intrinsic)
347 continue;
348
349 nir_intrinsic_instr *intrin = nir_instr_as_intrinsic(instr);
350
351 switch (intrin->intrinsic) {
352 case nir_intrinsic_load_deref: {
353 nir_deref_instr *deref = nir_src_as_deref(intrin->src[0]);
354 if (!nir_deref_mode_is(deref, nir_var_function_temp))
355 continue;
356
357 nir_variable *var = nir_deref_instr_get_variable(deref);
358 if (var == NULL)
359 continue;
360
361 struct var_info *info = &var_infos[var->index];
362 if (info->is_constant) {
363 b.cursor = nir_after_instr(&intrin->instr);
364 nir_ssa_def *val = build_constant_load(&b, deref, size_align);
365 nir_ssa_def_rewrite_uses(&intrin->dest.ssa,
366 val);
367 nir_instr_remove(&intrin->instr);
368 nir_deref_instr_remove_if_unused(deref);
369 }
370 break;
371 }
372
373 case nir_intrinsic_store_deref: {
374 nir_deref_instr *deref = nir_src_as_deref(intrin->src[0]);
375 if (!nir_deref_mode_is(deref, nir_var_function_temp))
376 continue;
377
378 nir_variable *var = nir_deref_instr_get_variable(deref);
379 if (var == NULL)
380 continue;
381
382 struct var_info *info = &var_infos[var->index];
383 if (info->is_constant) {
384 nir_instr_remove(&intrin->instr);
385 nir_deref_instr_remove_if_unused(deref);
386 }
387 break;
388 }
389 case nir_intrinsic_copy_deref:
390 default:
391 continue;
392 }
393 }
394 }
395
396 /* Clean up the now unused variables */
397 for (int i = 0; i < num_locals; i++) {
398 struct var_info *info = &var_infos[i];
399 if (info->is_constant)
400 exec_node_remove(&info->var->node);
401 }
402
403 ralloc_free(var_infos);
404
405 nir_metadata_preserve(impl, nir_metadata_block_index |
406 nir_metadata_dominance);
407 return true;
408 }
409