1/*
2 * Copyright © 2013 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_flatten_nested_if_blocks.cpp
26 *
27 * Flattens nested if blocks such as:
28 *
29 * if (x) {
30 *    if (y) {
31 *       ...
32 *    }
33 * }
34 *
35 * into a single if block with a combined condition:
36 *
37 * if (x && y) {
38 *    ...
39 * }
40 */
41
42#include "ir.h"
43#include "ir_builder.h"
44
45using namespace ir_builder;
46
47namespace {
48
49class nested_if_flattener : public ir_hierarchical_visitor {
50public:
51   nested_if_flattener()
52   {
53      progress = false;
54   }
55
56   ir_visitor_status visit_leave(ir_if *);
57   ir_visitor_status visit_enter(ir_assignment *);
58
59   bool progress;
60};
61
62} /* unnamed namespace */
63
64/* We only care about the top level "if" instructions, so don't
65 * descend into expressions.
66 */
67ir_visitor_status
68nested_if_flattener::visit_enter(ir_assignment *ir)
69{
70   (void) ir;
71   return visit_continue_with_parent;
72}
73
74bool
75opt_flatten_nested_if_blocks(exec_list *instructions)
76{
77   nested_if_flattener v;
78
79   v.run(instructions);
80   return v.progress;
81}
82
83
84ir_visitor_status
85nested_if_flattener::visit_leave(ir_if *ir)
86{
87   /* Only handle a single ir_if within the then clause of an ir_if.  No extra
88    * instructions, no else clauses, nothing.
89    */
90   if (ir->then_instructions.is_empty() || !ir->else_instructions.is_empty())
91      return visit_continue;
92
93   ir_if *inner = ((ir_instruction *) ir->then_instructions.get_head_raw())->as_if();
94   if (!inner || !inner->next->is_tail_sentinel() ||
95       !inner->else_instructions.is_empty())
96      return visit_continue;
97
98   ir->condition = logic_and(ir->condition, inner->condition);
99   inner->then_instructions.move_nodes_to(&ir->then_instructions);
100
101   progress = true;
102   return visit_continue;
103}
104