summaryrefslogtreecommitdiffstats
path: root/src/compiler/glsl/opt_copy_propagation.cpp
blob: b72ae5a5e11a8ebed5dcd54b5d71d2db0e2d5ecc (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
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
/*
 * Copyright © 2010 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.
 */

/**
 * \file opt_copy_propagation.cpp
 *
 * Moves usage of recently-copied variables to the previous copy of
 * the variable.
 *
 * This should reduce the number of MOV instructions in the generated
 * programs unless copy propagation is also done on the LIR, and may
 * help anyway by triggering other optimizations that live in the HIR.
 */

#include "ir.h"
#include "ir_visitor.h"
#include "ir_basic_block.h"
#include "ir_optimization.h"
#include "compiler/glsl_types.h"
#include "util/hash_table.h"
#include "util/set.h"

namespace {

class ir_copy_propagation_visitor : public ir_hierarchical_visitor {
public:
   ir_copy_propagation_visitor()
   {
      progress = false;
      mem_ctx = ralloc_context(0);
      lin_ctx = linear_alloc_parent(mem_ctx, 0);
      acp = _mesa_hash_table_create(mem_ctx, _mesa_hash_pointer,
                                    _mesa_key_pointer_equal);
      kills = _mesa_set_create(mem_ctx, _mesa_hash_pointer,
                               _mesa_key_pointer_equal);
      killed_all = false;
   }
   ~ir_copy_propagation_visitor()
   {
      ralloc_free(mem_ctx);
   }

   virtual ir_visitor_status visit(class ir_dereference_variable *);
   void handle_loop(class ir_loop *, bool keep_acp);
   virtual ir_visitor_status visit_enter(class ir_loop *);
   virtual ir_visitor_status visit_enter(class ir_function_signature *);
   virtual ir_visitor_status visit_enter(class ir_function *);
   virtual ir_visitor_status visit_leave(class ir_assignment *);
   virtual ir_visitor_status visit_enter(class ir_call *);
   virtual ir_visitor_status visit_enter(class ir_if *);

   void add_copy(ir_assignment *ir);
   void kill(ir_variable *ir);
   void handle_if_block(exec_list *instructions);

   /** Hash of lhs->rhs: The available copies to propagate */
   hash_table *acp;

   /**
    * Set of ir_variables: Whose values were killed in this block.
    */
   set *kills;

   bool progress;

   bool killed_all;

   void *mem_ctx;
   void *lin_ctx;
};

} /* unnamed namespace */

ir_visitor_status
ir_copy_propagation_visitor::visit_enter(ir_function_signature *ir)
{
   /* Treat entry into a function signature as a completely separate
    * block.  Any instructions at global scope will be shuffled into
    * main() at link time, so they're irrelevant to us.
    */
   hash_table *orig_acp = this->acp;
   set *orig_kills = this->kills;
   bool orig_killed_all = this->killed_all;

   acp = _mesa_hash_table_create(NULL, _mesa_hash_pointer,
                                 _mesa_key_pointer_equal);
   kills = _mesa_set_create(NULL, _mesa_hash_pointer,
                            _mesa_key_pointer_equal);
   this->killed_all = false;

   visit_list_elements(this, &ir->body);

   _mesa_hash_table_destroy(acp, NULL);
   _mesa_set_destroy(kills, NULL);

   this->kills = orig_kills;
   this->acp = orig_acp;
   this->killed_all = orig_killed_all;

   return visit_continue_with_parent;
}

ir_visitor_status
ir_copy_propagation_visitor::visit_leave(ir_assignment *ir)
{
   kill(ir->lhs->variable_referenced());

   add_copy(ir);

   return visit_continue;
}

ir_visitor_status
ir_copy_propagation_visitor::visit_enter(ir_function *ir)
{
   (void) ir;
   return visit_continue;
}

/**
 * Replaces dereferences of ACP RHS variables with ACP LHS variables.
 *
 * This is where the actual copy propagation occurs.  Note that the
 * rewriting of ir_dereference means that the ir_dereference instance
 * must not be shared by multiple IR operations!
 */
ir_visitor_status
ir_copy_propagation_visitor::visit(ir_dereference_variable *ir)
{
   if (this->in_assignee)
      return visit_continue;

   struct hash_entry *entry = _mesa_hash_table_search(acp, ir->var);
   if (entry) {
      ir->var = (ir_variable *) entry->data;
      progress = true;
   }

   return visit_continue;
}


ir_visitor_status
ir_copy_propagation_visitor::visit_enter(ir_call *ir)
{
   /* Do copy propagation on call parameters, but skip any out params */
   foreach_two_lists(formal_node, &ir->callee->parameters,
                     actual_node, &ir->actual_parameters) {
      ir_variable *sig_param = (ir_variable *) formal_node;
      ir_rvalue *ir = (ir_rvalue *) actual_node;
      if (sig_param->data.mode != ir_var_function_out
          && sig_param->data.mode != ir_var_function_inout) {
         ir->accept(this);
      }
   }

   /* Since this pass can run when unlinked, we don't (necessarily) know
    * the side effects of calls.  (When linked, most calls are inlined
    * anyway, so it doesn't matter much.)
    *
    * One place where this does matter is IR intrinsics.  They're never
    * inlined.  We also know what they do - while some have side effects
    * (such as image writes), none edit random global variables.  So we
    * can assume they're side-effect free (other than the return value
    * and out parameters).
    */
   if (!ir->callee->is_intrinsic()) {
      _mesa_hash_table_clear(acp, NULL);
      this->killed_all = true;
   } else {
      if (ir->return_deref)
         kill(ir->return_deref->var);

      foreach_two_lists(formal_node, &ir->callee->parameters,
                        actual_node, &ir->actual_parameters) {
         ir_variable *sig_param = (ir_variable *) formal_node;
         if (sig_param->data.mode == ir_var_function_out ||
             sig_param->data.mode == ir_var_function_inout) {
            ir_rvalue *ir = (ir_rvalue *) actual_node;
            ir_variable *var = ir->variable_referenced();
            kill(var);
         }
      }
   }

   return visit_continue_with_parent;
}

void
ir_copy_propagation_visitor::handle_if_block(exec_list *instructions)
{
   hash_table *orig_acp = this->acp;
   set *orig_kills = this->kills;
   bool orig_killed_all = this->killed_all;

   acp = _mesa_hash_table_create(NULL, _mesa_hash_pointer,
                                 _mesa_key_pointer_equal);
   kills = _mesa_set_create(NULL, _mesa_hash_pointer,
                            _mesa_key_pointer_equal);
   this->killed_all = false;

   /* Populate the initial acp with a copy of the original */
   struct hash_entry *entry;
   hash_table_foreach(orig_acp, entry) {
      _mesa_hash_table_insert(acp, entry->key, entry->data);
   }

   visit_list_elements(this, instructions);

   if (this->killed_all) {
      _mesa_hash_table_clear(orig_acp, NULL);
   }

   set *new_kills = this->kills;
   this->kills = orig_kills;
   _mesa_hash_table_destroy(acp, NULL);
   this->acp = orig_acp;
   this->killed_all = this->killed_all || orig_killed_all;

   struct set_entry *s_entry;
   set_foreach(new_kills, s_entry) {
      kill((ir_variable *) s_entry->key);
   }

   _mesa_set_destroy(new_kills, NULL);
}

ir_visitor_status
ir_copy_propagation_visitor::visit_enter(ir_if *ir)
{
   ir->condition->accept(this);

   handle_if_block(&ir->then_instructions);
   handle_if_block(&ir->else_instructions);

   /* handle_if_block() already descended into the children. */
   return visit_continue_with_parent;
}

void
ir_copy_propagation_visitor::handle_loop(ir_loop *ir, bool keep_acp)
{
   hash_table *orig_acp = this->acp;
   set *orig_kills = this->kills;
   bool orig_killed_all = this->killed_all;

   acp = _mesa_hash_table_create(NULL, _mesa_hash_pointer,
                                 _mesa_key_pointer_equal);
   kills = _mesa_set_create(NULL, _mesa_hash_pointer,
                            _mesa_key_pointer_equal);
   this->killed_all = false;

   if (keep_acp) {
      struct hash_entry *entry;
      hash_table_foreach(orig_acp, entry) {
         _mesa_hash_table_insert(acp, entry->key, entry->data);
      }
   }

   visit_list_elements(this, &ir->body_instructions);

   if (this->killed_all) {
      _mesa_hash_table_clear(orig_acp, NULL);
   }

   set *new_kills = this->kills;
   this->kills = orig_kills;
   _mesa_hash_table_destroy(acp, NULL);
   this->acp = orig_acp;
   this->killed_all = this->killed_all || orig_killed_all;

   struct set_entry *entry;
   set_foreach(new_kills, entry) {
      kill((ir_variable *) entry->key);
   }

   _mesa_set_destroy(new_kills, NULL);
}

ir_visitor_status
ir_copy_propagation_visitor::visit_enter(ir_loop *ir)
{
   /* Make a conservative first pass over the loop with an empty ACP set.
    * This also removes any killed entries from the original ACP set.
    */
   handle_loop(ir, false);

   /* Then, run it again with the real ACP set, minus any killed entries.
    * This takes care of propagating values from before the loop into it.
    */
   handle_loop(ir, true);

   /* already descended into the children. */
   return visit_continue_with_parent;
}

void
ir_copy_propagation_visitor::kill(ir_variable *var)
{
   assert(var != NULL);

   /* Remove any entries currently in the ACP for this kill. */
   struct hash_entry *entry = _mesa_hash_table_search(acp, var);
   if (entry) {
      _mesa_hash_table_remove(acp, entry);
   }

   hash_table_foreach(acp, entry) {
      if (var == (ir_variable *) entry->data) {
         _mesa_hash_table_remove(acp, entry);
      }
   }

   /* Add the LHS variable to the set of killed variables in this block. */
   _mesa_set_add(kills, var);
}

/**
 * Adds an entry to the available copy list if it's a plain assignment
 * of a variable to a variable.
 */
void
ir_copy_propagation_visitor::add_copy(ir_assignment *ir)
{
   if (ir->condition)
      return;

   ir_variable *lhs_var = ir->whole_variable_written();
   ir_variable *rhs_var = ir->rhs->whole_variable_referenced();

   if ((lhs_var != NULL) && (rhs_var != NULL)) {
      if (lhs_var == rhs_var) {
	 /* This is a dumb assignment, but we've conveniently noticed
	  * it here.  Removing it now would mess up the loop iteration
	  * calling us.  Just flag it to not execute, and someone else
	  * will clean up the mess.
	  */
	 ir->condition = new(ralloc_parent(ir)) ir_constant(false);
	 this->progress = true;
      } else if (lhs_var->data.mode != ir_var_shader_storage &&
                 lhs_var->data.mode != ir_var_shader_shared &&
                 lhs_var->data.precise == rhs_var->data.precise) {
         assert(lhs_var);
         assert(rhs_var);
         _mesa_hash_table_insert(acp, lhs_var, rhs_var);
      }
   }
}

/**
 * Does a copy propagation pass on the code present in the instruction stream.
 */
bool
do_copy_propagation(exec_list *instructions)
{
   ir_copy_propagation_visitor v;

   visit_list_elements(&v, instructions);

   return v.progress;
}