1/*
2 * Copyright (C) 2017 Apple Inc. All rights reserved.
3 *
4 * Redistribution and use in source and binary forms, with or without
5 * modification, are permitted provided that the following conditions
6 * are met:
7 * 1. Redistributions of source code must retain the above copyright
8 * notice, this list of conditions and the following disclaimer.
9 * 2. Redistributions in binary form must reproduce the above copyright
10 * notice, this list of conditions and the following disclaimer in the
11 * documentation and/or other materials provided with the distribution.
12 *
13 * THIS SOFTWARE IS PROVIDED BY APPLE INC. ``AS IS'' AND ANY
14 * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
15 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
16 * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL APPLE INC. OR
17 * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
18 * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
19 * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
20 * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY
21 * OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
22 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
23 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
24 */
25
26#include "config.h"
27#include "B3EnsureLoopPreHeaders.h"
28
29#if ENABLE(B3_JIT)
30
31#include "B3BasicBlockInlines.h"
32#include "B3BlockInsertionSet.h"
33#include "B3NaturalLoops.h"
34#include "B3ProcedureInlines.h"
35#include "B3ValueInlines.h"
36
37namespace JSC { namespace B3 {
38
39bool ensureLoopPreHeaders(Procedure& proc)
40{
41 NaturalLoops& loops = proc.naturalLoops();
42
43 BlockInsertionSet insertionSet(proc);
44
45 for (unsigned loopIndex = loops.numLoops(); loopIndex--;) {
46 const NaturalLoop& loop = loops.loop(loopIndex);
47
48 Vector<BasicBlock*, 4> outOfBodyPredecessors;
49 double totalFrequency = 0;
50 for (BasicBlock* predecessor : loop.header()->predecessors()) {
51 if (loops.belongsTo(predecessor, loop))
52 continue;
53
54 outOfBodyPredecessors.append(predecessor);
55 totalFrequency += predecessor->frequency();
56 }
57
58 if (outOfBodyPredecessors.size() <= 1)
59 continue;
60
61 BasicBlock* preHeader = insertionSet.insertBefore(loop.header(), totalFrequency);
62 preHeader->appendNew<Value>(proc, Jump, loop.header()->at(0)->origin());
63 preHeader->setSuccessors(FrequentedBlock(loop.header()));
64
65 for (BasicBlock* predecessor : outOfBodyPredecessors) {
66 predecessor->replaceSuccessor(loop.header(), preHeader);
67 preHeader->addPredecessor(predecessor);
68 loop.header()->removePredecessor(predecessor);
69 }
70
71 loop.header()->addPredecessor(preHeader);
72 }
73
74 if (insertionSet.execute()) {
75 proc.invalidateCFG();
76 return true;
77 }
78
79 return false;
80}
81
82} } // namespace JSC::B3
83
84#endif // ENABLE(B3_JIT)
85
86