aboutsummaryrefslogtreecommitdiffstats
path: root/src/compiler/nir/nir_split_var_copies.c
blob: bc3ceedbdb8b7481770f85442355457750167aa8 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
/*
 * Copyright © 2014 Intel Corporation
 *
 * Permission is hereby granted, free of charge, to any person obtaining a
 * copy of this software and associated documentation files (the "Software"),
 * to deal in the Software without restriction, including without limitation
 * the rights to use, copy, modify, merge, publish, distribute, sublicense,
 * and/or sell copies of the Software, and to permit persons to whom the
 * Software is furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice (including the next
 * paragraph) shall be included in all copies or substantial portions of the
 * Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
 * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
 * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
 * IN THE SOFTWARE.
 *
 * Authors:
 *    Jason Ekstrand (jason@jlekstrand.net)
 *
 */

#include "nir.h"

/*
 * Implements "copy splitting" which is similar to structure splitting only
 * it works on copy operations rather than the datatypes themselves.  The
 * GLSL language allows you to copy one variable to another an entire
 * structure (which may contain arrays or other structures) at a time.
 * Normally, in a language such as C this would be handled by a "structure
 * splitting" pass that breaks up the structures.  Unfortunately for us,
 * structures used in inputs or outputs can't be split.  Therefore,
 * regardlesss of what we do, we have to be able to copy to/from
 * structures.
 *
 * The primary purpose of structure splitting is to allow you to better
 * optimize variable access and lower things to registers where you can.
 * The primary issue here is that, if you lower the copy to a bunch of
 * loads and stores, you loose a lot of information about the copy
 * operation that you would like to keep around.  To solve this problem, we
 * have a "copy splitting" pass that, instead of splitting the structures
 * or lowering the copy into loads and storres, splits the copy operation
 * into a bunch of copy operations one for each leaf of the structure tree.
 * If an intermediate array is encountered, it is referenced with a
 * wildcard reference to indicate that the entire array is to be copied.
 *
 * As things become direct, array copies may be able to be losslessly
 * lowered to having fewer and fewer wildcards.  However, until that
 * happens we want to keep the information about the arrays intact.
 *
 * Prior to the copy splitting pass, there are no wildcard references but
 * there may be incomplete references where the tail of the deref chain is
 * an array or a structure and not a specific element.  After the copy
 * splitting pass has completed, every variable deref will be a full-length
 * dereference pointing to a single leaf in the structure type tree with
 * possibly a few wildcard array dereferences.
 */

struct split_var_copies_state {
   nir_shader *shader;
   void *dead_ctx;
   bool progress;
};

/* Recursively constructs deref chains to split a copy instruction into
 * multiple (if needed) copy instructions with full-length deref chains.
 * External callers of this function should pass the tail and head of the
 * deref chains found as the source and destination of the copy instruction
 * into this function.
 *
 * \param  old_copy  The copy instruction we are splitting
 * \param  dest_head The head of the destination deref chain we are building
 * \param  src_head  The head of the source deref chain we are building
 * \param  dest_tail The tail of the destination deref chain we are building
 * \param  src_tail  The tail of the source deref chain we are building
 * \param  state     The current split_var_copies_state object
 */
static void
split_var_copy_instr(nir_intrinsic_instr *old_copy,
                     nir_deref_var *dest_head, nir_deref_var *src_head,
                     nir_deref *dest_tail, nir_deref *src_tail,
                     struct split_var_copies_state *state)
{
   assert(src_tail->type == dest_tail->type);

   /* Make sure these really are the tails of the deref chains */
   assert(dest_tail->child == NULL);
   assert(src_tail->child == NULL);

   switch (glsl_get_base_type(src_tail->type)) {
   case GLSL_TYPE_ARRAY: {
      /* Make a wildcard dereference */
      nir_deref_array *deref = nir_deref_array_create(state->dead_ctx);
      deref->deref.type = glsl_get_array_element(src_tail->type);
      deref->deref_array_type = nir_deref_array_type_wildcard;

      /* Set the tail of both as the newly created wildcard deref.  It is
       * safe to use the same wildcard in both places because a) we will be
       * copying it before we put it in an actual instruction and b)
       * everything that will potentially add another link in the deref
       * chain will also add the same thing to both chains.
       */
      src_tail->child = &deref->deref;
      dest_tail->child = &deref->deref;

      split_var_copy_instr(old_copy, dest_head, src_head,
                           dest_tail->child, src_tail->child, state);

      /* Set it back to the way we found it */
      src_tail->child = NULL;
      dest_tail->child = NULL;
      break;
   }

   case GLSL_TYPE_STRUCT:
      /* This is the only part that actually does any interesting
       * splitting.  For array types, we just use wildcards and resolve
       * them later.  For structure types, we need to emit one copy
       * instruction for every structure element.  Because we may have
       * structs inside structs, we just recurse and let the next level
       * take care of any additional structures.
       */
      for (unsigned i = 0; i < glsl_get_length(src_tail->type); i++) {
         nir_deref_struct *deref = nir_deref_struct_create(state->dead_ctx, i);
         deref->deref.type = glsl_get_struct_field(src_tail->type, i);

         /* Set the tail of both as the newly created structure deref.  It
          * is safe to use the same wildcard in both places because a) we
          * will be copying it before we put it in an actual instruction
          * and b) everything that will potentially add another link in the
          * deref chain will also add the same thing to both chains.
          */
         src_tail->child = &deref->deref;
         dest_tail->child = &deref->deref;

         split_var_copy_instr(old_copy, dest_head, src_head,
                              dest_tail->child, src_tail->child, state);
      }
      /* Set it back to the way we found it */
      src_tail->child = NULL;
      dest_tail->child = NULL;
      break;

   case GLSL_TYPE_UINT:
   case GLSL_TYPE_UINT16:
   case GLSL_TYPE_UINT64:
   case GLSL_TYPE_INT:
   case GLSL_TYPE_INT16:
   case GLSL_TYPE_INT64:
   case GLSL_TYPE_FLOAT:
   case GLSL_TYPE_FLOAT16:
   case GLSL_TYPE_DOUBLE:
   case GLSL_TYPE_BOOL:
      if (glsl_type_is_matrix(src_tail->type)) {
         nir_deref_array *deref = nir_deref_array_create(state->dead_ctx);
         deref->deref.type = glsl_get_column_type(src_tail->type);
         deref->deref_array_type = nir_deref_array_type_wildcard;

         /* Set the tail of both as the newly created wildcard deref.  It
          * is safe to use the same wildcard in both places because a) we
          * will be copying it before we put it in an actual instruction
          * and b) everything that will potentially add another link in the
          * deref chain will also add the same thing to both chains.
          */
         src_tail->child = &deref->deref;
         dest_tail->child = &deref->deref;

         split_var_copy_instr(old_copy, dest_head, src_head,
                              dest_tail->child, src_tail->child, state);

         /* Set it back to the way we found it */
         src_tail->child = NULL;
         dest_tail->child = NULL;
      } else {
         /* At this point, we have fully built our deref chains and can
          * actually add the new copy instruction.
          */
         nir_intrinsic_instr *new_copy =
            nir_intrinsic_instr_create(state->shader, nir_intrinsic_copy_var);

         /* We need to make copies because a) this deref chain actually
          * belongs to the copy instruction and b) the deref chains may
          * have some of the same links due to the way we constructed them
          */
         new_copy->variables[0] = nir_deref_var_clone(dest_head, new_copy);
         new_copy->variables[1] = nir_deref_var_clone(src_head, new_copy);

         /* Emit the copy instruction after the old instruction.  We'll
          * remove the old one later.
          */
         nir_instr_insert_after(&old_copy->instr, &new_copy->instr);
         state->progress = true;
      }
      break;

   case GLSL_TYPE_SAMPLER:
   case GLSL_TYPE_IMAGE:
   case GLSL_TYPE_ATOMIC_UINT:
   case GLSL_TYPE_INTERFACE:
   default:
      unreachable("Cannot copy these types");
   }
}

static bool
split_var_copies_block(nir_block *block, struct split_var_copies_state *state)
{
   nir_foreach_instr_safe(instr, block) {
      if (instr->type != nir_instr_type_intrinsic)
         continue;

      nir_intrinsic_instr *intrinsic = nir_instr_as_intrinsic(instr);
      if (intrinsic->intrinsic != nir_intrinsic_copy_var)
         continue;

      nir_deref_var *dest_head = intrinsic->variables[0];
      nir_deref_var *src_head = intrinsic->variables[1];
      nir_deref *dest_tail = nir_deref_tail(&dest_head->deref);
      nir_deref *src_tail = nir_deref_tail(&src_head->deref);

      switch (glsl_get_base_type(src_tail->type)) {
      case GLSL_TYPE_ARRAY:
      case GLSL_TYPE_STRUCT:
         split_var_copy_instr(intrinsic, dest_head, src_head,
                              dest_tail, src_tail, state);
         nir_instr_remove(&intrinsic->instr);
         ralloc_steal(state->dead_ctx, instr);
         break;
      case GLSL_TYPE_FLOAT:
      case GLSL_TYPE_FLOAT16:
      case GLSL_TYPE_DOUBLE:
         if (glsl_type_is_matrix(src_tail->type)) {
            split_var_copy_instr(intrinsic, dest_head, src_head,
                                 dest_tail, src_tail, state);
            nir_instr_remove(&intrinsic->instr);
            ralloc_steal(state->dead_ctx, instr);
         }
         break;
      case GLSL_TYPE_INT:
      case GLSL_TYPE_UINT:
      case GLSL_TYPE_INT16:
      case GLSL_TYPE_UINT16:
      case GLSL_TYPE_INT64:
      case GLSL_TYPE_UINT64:
      case GLSL_TYPE_BOOL:
         assert(!glsl_type_is_matrix(src_tail->type));
         break;
      default:
         unreachable("Invalid type");
         break;
      }
   }

   return true;
}

static bool
split_var_copies_impl(nir_function_impl *impl)
{
   struct split_var_copies_state state;

   state.shader = impl->function->shader;
   state.dead_ctx = ralloc_context(NULL);
   state.progress = false;

   nir_foreach_block(block, impl) {
      split_var_copies_block(block, &state);
   }

   ralloc_free(state.dead_ctx);

   if (state.progress) {
      nir_metadata_preserve(impl, nir_metadata_block_index |
                                  nir_metadata_dominance);
   }

   return state.progress;
}

bool
nir_split_var_copies(nir_shader *shader)
{
   bool progress = false;

   nir_foreach_function(function, shader) {
      if (function->impl)
         progress = split_var_copies_impl(function->impl) || progress;
   }

   return progress;
}