aboutsummaryrefslogtreecommitdiff
path: root/mesalib/src/glsl/opt_constant_propagation.cpp
blob: 4425f4211934a0dd5f913e1048a2365f24419fda (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
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
/*
 * Copyright © 2010 Intel Corporation
 *
 * Permission is hereby granted, free of charge, to any person obtaining a
 * constant of this software and associated documentation files (the "Software"),
 * to deal in the Software without restriction, including without limitation
 * the rights to use, constant, 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 constantright 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 CONSTANTRIGHT 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_constant_propagation.cpp
 *
 * Tracks assignments of constants to channels of variables, and
 * usage of those constant channels with direct usage of the constants.
 *
 * This can lead to constant folding and algebraic optimizations in
 * those later expressions, while causing no increase in instruction
 * count (due to constants being generally free to load from a
 * constant push buffer or as instruction immediate values) and
 * possibly reducing register pressure.
 */

#include "ir.h"
#include "ir_visitor.h"
#include "ir_rvalue_visitor.h"
#include "ir_basic_block.h"
#include "ir_optimization.h"
#include "glsl_types.h"

class acp_entry : public exec_node
{
public:
   acp_entry(ir_variable *var, unsigned write_mask, ir_constant *constant)
   {
      assert(var);
      assert(constant);
      this->var = var;
      this->write_mask = write_mask;
      this->constant = constant;
   }

   ir_variable *var;
   ir_constant *constant;
   unsigned write_mask;
};


class kill_entry : public exec_node
{
public:
   kill_entry(ir_variable *var, unsigned write_mask)
   {
      assert(var);
      this->var = var;
      this->write_mask = write_mask;
   }

   ir_variable *var;
   unsigned write_mask;
};

class ir_constant_propagation_visitor : public ir_rvalue_visitor {
public:
   ir_constant_propagation_visitor()
   {
      progress = false;
      mem_ctx = ralloc_context(0);
      this->acp = new(mem_ctx) exec_list;
      this->kills = new(mem_ctx) exec_list;
   }
   ~ir_constant_propagation_visitor()
   {
      ralloc_free(mem_ctx);
   }

   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_constant(ir_assignment *ir);
   void kill(ir_variable *ir, unsigned write_mask);
   void handle_if_block(exec_list *instructions);
   void handle_rvalue(ir_rvalue **rvalue);

   /** List of acp_entry: The available constants to propagate */
   exec_list *acp;

   /**
    * List of kill_entry: The masks of variables whose values were
    * killed in this block.
    */
   exec_list *kills;

   bool progress;

   bool killed_all;

   void *mem_ctx;
};


void
ir_constant_propagation_visitor::handle_rvalue(ir_rvalue **rvalue)
{
   if (this->in_assignee || !*rvalue)
      return;

   const glsl_type *type = (*rvalue)->type;
   if (!type->is_scalar() && !type->is_vector())
      return;

   ir_swizzle *swiz = NULL;
   ir_dereference_variable *deref = (*rvalue)->as_dereference_variable();
   if (!deref) {
      swiz = (*rvalue)->as_swizzle();
      if (!swiz)
	 return;

      deref = swiz->val->as_dereference_variable();
      if (!deref)
	 return;
   }

   ir_constant_data data;
   memset(&data, 0, sizeof(data));

   for (unsigned int i = 0; i < type->components(); i++) {
      int channel;
      acp_entry *found = NULL;

      if (swiz) {
	 switch (i) {
	 case 0: channel = swiz->mask.x; break;
	 case 1: channel = swiz->mask.y; break;
	 case 2: channel = swiz->mask.z; break;
	 case 3: channel = swiz->mask.w; break;
	 default: assert(!"shouldn't be reached"); channel = 0; break;
	 }
      } else {
	 channel = i;
      }

      foreach_iter(exec_list_iterator, iter, *this->acp) {
	 acp_entry *entry = (acp_entry *)iter.get();
	 if (entry->var == deref->var && entry->write_mask & (1 << channel)) {
	    found = entry;
	    break;
	 }
      }

      if (!found)
	 return;

      int rhs_channel = 0;
      for (int j = 0; j < 4; j++) {
	 if (j == channel)
	    break;
	 if (found->write_mask & (1 << j))
	    rhs_channel++;
      }

      switch (type->base_type) {
      case GLSL_TYPE_FLOAT:
	 data.f[i] = found->constant->value.f[rhs_channel];
	 break;
      case GLSL_TYPE_INT:
	 data.i[i] = found->constant->value.i[rhs_channel];
	 break;
      case GLSL_TYPE_UINT:
	 data.u[i] = found->constant->value.u[rhs_channel];
	 break;
      case GLSL_TYPE_BOOL:
	 data.b[i] = found->constant->value.b[rhs_channel];
	 break;
      default:
	 assert(!"not reached");
	 break;
      }
   }

   *rvalue = new(ralloc_parent(deref)) ir_constant(type, &data);
   this->progress = true;
}

ir_visitor_status
ir_constant_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.
    */
   exec_list *orig_acp = this->acp;
   exec_list *orig_kills = this->kills;
   bool orig_killed_all = this->killed_all;

   this->acp = new(mem_ctx) exec_list;
   this->kills = new(mem_ctx) exec_list;
   this->killed_all = false;

   visit_list_elements(this, &ir->body);

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

   return visit_continue_with_parent;
}

ir_visitor_status
ir_constant_propagation_visitor::visit_leave(ir_assignment *ir)
{
   if (this->in_assignee)
      return visit_continue;

   kill(ir->lhs->variable_referenced(), ir->write_mask);

   add_constant(ir);

   return visit_continue;
}

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

ir_visitor_status
ir_constant_propagation_visitor::visit_enter(ir_call *ir)
{
   /* Do constant propagation on call parameters, but skip any out params */
   exec_list_iterator sig_param_iter = ir->get_callee()->parameters.iterator();
   foreach_iter(exec_list_iterator, iter, ir->actual_parameters) {
      ir_variable *sig_param = (ir_variable *)sig_param_iter.get();
      ir_rvalue *param = (ir_rvalue *)iter.get();
      if (sig_param->mode != ir_var_out && sig_param->mode != ir_var_inout) {
	 ir_rvalue *new_param = param;
	 handle_rvalue(&new_param);
         if (new_param != param)
	    param->replace_with(new_param);
	 else
	    param->accept(this);
      }
      sig_param_iter.next();
   }

   /* Since we're unlinked, we don't (necssarily) know the side effects of
    * this call.  So kill all copies.
    */
   acp->make_empty();
   this->killed_all = true;

   return visit_continue_with_parent;
}

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

   this->acp = new(mem_ctx) exec_list;
   this->kills = new(mem_ctx) exec_list;
   this->killed_all = false;

   /* Populate the initial acp with a constant of the original */
   foreach_iter(exec_list_iterator, iter, *orig_acp) {
      acp_entry *a = (acp_entry *)iter.get();
      this->acp->push_tail(new(this->mem_ctx) acp_entry(a->var, a->write_mask,
							a->constant));
   }

   visit_list_elements(this, instructions);

   if (this->killed_all) {
      orig_acp->make_empty();
   }

   exec_list *new_kills = this->kills;
   this->kills = orig_kills;
   this->acp = orig_acp;
   this->killed_all = this->killed_all || orig_killed_all;

   foreach_iter(exec_list_iterator, iter, *new_kills) {
      kill_entry *k = (kill_entry *)iter.get();
      kill(k->var, k->write_mask);
   }
}

ir_visitor_status
ir_constant_propagation_visitor::visit_enter(ir_if *ir)
{
   ir->condition->accept(this);
   handle_rvalue(&ir->condition);

   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;
}

ir_visitor_status
ir_constant_propagation_visitor::visit_enter(ir_loop *ir)
{
   exec_list *orig_acp = this->acp;
   exec_list *orig_kills = this->kills;
   bool orig_killed_all = this->killed_all;

   /* FINISHME: For now, the initial acp for loops is totally empty.
    * We could go through once, then go through again with the acp
    * cloned minus the killed entries after the first run through.
    */
   this->acp = new(mem_ctx) exec_list;
   this->kills = new(mem_ctx) exec_list;
   this->killed_all = false;

   visit_list_elements(this, &ir->body_instructions);

   if (this->killed_all) {
      orig_acp->make_empty();
   }

   exec_list *new_kills = this->kills;
   this->kills = orig_kills;
   this->acp = orig_acp;
   this->killed_all = this->killed_all || orig_killed_all;

   foreach_iter(exec_list_iterator, iter, *new_kills) {
      kill_entry *k = (kill_entry *)iter.get();
      kill(k->var, k->write_mask);
   }

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

void
ir_constant_propagation_visitor::kill(ir_variable *var, unsigned write_mask)
{
   assert(var != NULL);

   /* We don't track non-vectors. */
   if (!var->type->is_vector() && !var->type->is_scalar())
      return;

   /* Remove any entries currently in the ACP for this kill. */
   foreach_iter(exec_list_iterator, iter, *this->acp) {
      acp_entry *entry = (acp_entry *)iter.get();

      if (entry->var == var) {
	 entry->write_mask &= ~write_mask;
	 if (entry->write_mask == 0)
	    entry->remove();
      }
   }

   /* Add this writemask of the variable to the list of killed
    * variables in this block.
    */
   foreach_iter(exec_list_iterator, iter, *this->kills) {
      kill_entry *entry = (kill_entry *)iter.get();

      if (entry->var == var) {
	 entry->write_mask |= write_mask;
	 return;
      }
   }
   /* Not already in the list.  Make new entry. */
   this->kills->push_tail(new(this->mem_ctx) kill_entry(var, write_mask));
}

/**
 * Adds an entry to the available constant list if it's a plain assignment
 * of a variable to a variable.
 */
void
ir_constant_propagation_visitor::add_constant(ir_assignment *ir)
{
   acp_entry *entry;

   if (ir->condition)
      return;

   if (!ir->write_mask)
      return;

   ir_dereference_variable *deref = ir->lhs->as_dereference_variable();
   ir_constant *constant = ir->rhs->as_constant();

   if (!deref || !constant)
      return;

   /* Only do constant propagation on vectors.  Constant matrices,
    * arrays, or structures would require more work elsewhere.
    */
   if (!deref->var->type->is_vector() && !deref->var->type->is_scalar())
      return;

   entry = new(this->mem_ctx) acp_entry(deref->var, ir->write_mask, constant);
   this->acp->push_tail(entry);
}

/**
 * Does a constant propagation pass on the code present in the instruction stream.
 */
bool
do_constant_propagation(exec_list *instructions)
{
   ir_constant_propagation_visitor v;

   visit_list_elements(&v, instructions);

   return v.progress;
}