1 /*
2 * Copyright © 2018 Valve 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 * Daniel Schürmann (daniel.schuermann@campus.tu-berlin.de)
25 *
26 */
27
28 #ifndef ACO_DOMINANCE_CPP
29 #define ACO_DOMINANCE_CPP
30
31 #include "aco_ir.h"
32
33 /*
34 * Implements the algorithms for computing the dominator tree from
35 * "A Simple, Fast Dominance Algorithm" by Cooper, Harvey, and Kennedy.
36 *
37 * Different from the paper, our CFG allows to compute the dominator tree
38 * in a single pass as it is guaranteed that the dominating predecessors
39 * are processed before the current block.
40 */
41
42 namespace aco {
43
dominator_tree(Program * program)44 void dominator_tree(Program* program)
45 {
46 program->blocks[0].logical_idom = 0;
47 program->blocks[0].linear_idom = 0;
48
49 for (unsigned i = 1; i < program->blocks.size(); i++) {
50 Block& block = program->blocks[i];
51 int new_logical_idom = -1;
52 int new_linear_idom = -1;
53 for (unsigned pred_idx : block.logical_preds) {
54 if ((int) program->blocks[pred_idx].logical_idom == -1)
55 continue;
56
57 if (new_logical_idom == -1) {
58 new_logical_idom = pred_idx;
59 continue;
60 }
61
62 while ((int) pred_idx != new_logical_idom) {
63 if ((int) pred_idx > new_logical_idom)
64 pred_idx = program->blocks[pred_idx].logical_idom;
65 if ((int) pred_idx < new_logical_idom)
66 new_logical_idom = program->blocks[new_logical_idom].logical_idom;
67 }
68 }
69
70 for (unsigned pred_idx : block.linear_preds) {
71 if ((int) program->blocks[pred_idx].linear_idom == -1)
72 continue;
73
74 if (new_linear_idom == -1) {
75 new_linear_idom = pred_idx;
76 continue;
77 }
78
79 while ((int) pred_idx != new_linear_idom) {
80 if ((int) pred_idx > new_linear_idom)
81 pred_idx = program->blocks[pred_idx].linear_idom;
82 if ((int) pred_idx < new_linear_idom)
83 new_linear_idom = program->blocks[new_linear_idom].linear_idom;
84 }
85 }
86
87 block.logical_idom = new_logical_idom;
88 block.linear_idom = new_linear_idom;
89 }
90 }
91
92 }
93 #endif
94