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
31class redundant_jumps_visitor : public ir_hierarchical_visitor {
32public:
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
45ir_visitor_status
46redundant_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
86ir_visitor_status
87redundant_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
104bool
105optimize_redundant_jumps(exec_list *instructions)
106{
107   redundant_jumps_visitor v;
108
109   v.run(instructions);
110   return v.progress;
111}
112