1 /*
2 * Copyright © 2010 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
21 * DEALINGS IN THE SOFTWARE.
22 */
23
24 /**
25 * \file opt_redundant_jumps.cpp
26 * Remove certain types of redundant jumps
27 */
28
29 #include "ir.h"
30
31 class redundant_jumps_visitor : public ir_hierarchical_visitor {
32 public:
redundant_jumps_visitor()33 redundant_jumps_visitor()
34 {
35 this->progress = false;
36 }
37
38 virtual ir_visitor_status visit_leave(ir_if *);
39 virtual ir_visitor_status visit_leave(ir_loop *);
40
41 bool progress;
42 };
43
44
45 ir_visitor_status
visit_leave(ir_if * ir)46 redundant_jumps_visitor::visit_leave(ir_if *ir)
47 {
48 /* If the last instruction in both branches is a 'break' or a 'continue',
49 * pull it out of the branches and insert it after the if-statment. Note
50 * that both must be the same type (either 'break' or 'continue').
51 */
52 ir_instruction *const last_then =
53 (ir_instruction *) ir->then_instructions.get_tail();
54 ir_instruction *const last_else =
55 (ir_instruction *) ir->else_instructions.get_tail();
56
57 if ((last_then == NULL) || (last_else == NULL))
58 return visit_continue;
59
60 if ((last_then->ir_type != ir_type_loop_jump)
61 || (last_else->ir_type != ir_type_loop_jump))
62 return visit_continue;
63
64 ir_loop_jump *const then_jump = (ir_loop_jump *) last_then;
65 ir_loop_jump *const else_jump = (ir_loop_jump *) last_else;
66
67 if (then_jump->mode != else_jump->mode)
68 return visit_continue;
69
70 then_jump->remove();
71 else_jump->remove();
72 this->progress = true;
73
74 ir->insert_after(then_jump);
75
76 /* If both branchs of the if-statement are now empty, remove the
77 * if-statement.
78 */
79 if (ir->then_instructions.is_empty() && ir->else_instructions.is_empty())
80 ir->remove();
81
82 return visit_continue;
83 }
84
85
86 ir_visitor_status
visit_leave(ir_loop * ir)87 redundant_jumps_visitor::visit_leave(ir_loop *ir)
88 {
89 /* If the last instruction of a loop body is a 'continue', remove it.
90 */
91 ir_instruction *const last =
92 (ir_instruction *) ir->body_instructions.get_tail();
93
94 if (last && (last->ir_type == ir_type_loop_jump)
95 && (((ir_loop_jump *) last)->mode == ir_loop_jump::jump_continue)) {
96 last->remove();
97 this->progress = true;
98 }
99
100 return visit_continue;
101 }
102
103
104 bool
optimize_redundant_jumps(exec_list * instructions)105 optimize_redundant_jumps(exec_list *instructions)
106 {
107 redundant_jumps_visitor v;
108
109 v.run(instructions);
110 return v.progress;
111 }
112