nir_opt_cse.c revision 7e102996 
1/*
2 * Copyright © 2014 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 * Authors:
24 *    Jason Ekstrand (jason@jlekstrand.net)
25 *    Connor Abbott (cwabbott0@gmail.com)
26 *
27 */
28
29#include "nir_instr_set.h"
30
31/*
32 * Implements common subexpression elimination
33 */
34
35/*
36 * Visits and CSEs the given block and all its descendants in the dominance
37 * tree recursively. Note that the instr_set is guaranteed to only ever
38 * contain instructions that dominate the current block.
39 */
40
41static bool
42cse_block(nir_block *block, struct set *dominance_set)
43{
44   bool progress = false;
45   struct set *instr_set = _mesa_set_clone(dominance_set, NULL);
46
47   nir_foreach_instr_safe(instr, block) {
48      if (nir_instr_set_add_or_rewrite(instr_set, instr)) {
49         progress = true;
50         nir_instr_remove(instr);
51      }
52   }
53
54   for (unsigned i = 0; i < block->num_dom_children; i++) {
55      nir_block *child = block->dom_children[i];
56      progress |= cse_block(child, instr_set);
57   }
58
59   _mesa_set_destroy(instr_set, NULL);
60
61   return progress;
62}
63
64static bool
65nir_opt_cse_impl(nir_function_impl *impl)
66{
67   struct set *instr_set = nir_instr_set_create(NULL);
68
69   nir_metadata_require(impl, nir_metadata_dominance);
70
71   bool progress = cse_block(nir_start_block(impl), instr_set);
72
73   if (progress) {
74      nir_metadata_preserve(impl, nir_metadata_block_index |
75                                  nir_metadata_dominance);
76   } else {
77#ifndef NDEBUG
78      impl->valid_metadata &= ~nir_metadata_not_properly_reset;
79#endif
80   }
81
82   nir_instr_set_destroy(instr_set);
83   return progress;
84}
85
86bool
87nir_opt_cse(nir_shader *shader)
88{
89   bool progress = false;
90
91   nir_foreach_function(function, shader) {
92      if (function->impl)
93         progress |= nir_opt_cse_impl(function->impl);
94   }
95
96   return progress;
97}
98
99