1/*
2 * Copyright (C) 2013 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 "DFGCriticalEdgeBreakingPhase.h"
28
29#if ENABLE(DFG_JIT)
30
31#include "DFGBasicBlockInlines.h"
32#include "DFGBlockInsertionSet.h"
33#include "DFGGraph.h"
34#include "DFGPhase.h"
35#include "JSCInlines.h"
36
37namespace JSC { namespace DFG {
38
39class CriticalEdgeBreakingPhase : public Phase {
40public:
41 CriticalEdgeBreakingPhase(Graph& graph)
42 : Phase(graph, "critical edge breaking")
43 , m_insertionSet(graph)
44 {
45 }
46
47 bool run()
48 {
49 for (BlockIndex blockIndex = 0; blockIndex < m_graph.numBlocks(); ++blockIndex) {
50 BasicBlock* block = m_graph.block(blockIndex);
51 if (!block)
52 continue;
53
54 // An edge A->B is critical if A has multiple successor and B has multiple
55 // predecessors. Thus we fail early if we don't have multiple successors.
56
57 if (block->numSuccessors() <= 1)
58 continue;
59
60 // Break critical edges by inserting a "Jump" pad block in place of each
61 // unique A->B critical edge.
62 HashMap<BasicBlock*, BasicBlock*> successorPads;
63
64 for (unsigned i = block->numSuccessors(); i--;) {
65 BasicBlock** successor = &block->successor(i);
66 if ((*successor)->predecessors.size() <= 1)
67 continue;
68
69 BasicBlock* pad = nullptr;
70 auto iter = successorPads.find(*successor);
71
72 if (iter == successorPads.end()) {
73 pad = m_insertionSet.insertBefore(*successor, (*successor)->executionCount);
74 pad->appendNode(
75 m_graph, SpecNone, Jump, (*successor)->at(0)->origin, OpInfo(*successor));
76 pad->predecessors.append(block);
77 (*successor)->replacePredecessor(block, pad);
78 successorPads.set(*successor, pad);
79 } else
80 pad = iter->value;
81
82 *successor = pad;
83 }
84 }
85
86 return m_insertionSet.execute();
87 }
88
89private:
90 BlockInsertionSet m_insertionSet;
91};
92
93bool performCriticalEdgeBreaking(Graph& graph)
94{
95 return runPhase<CriticalEdgeBreakingPhase>(graph);
96}
97
98} } // namespace JSC::DFG
99
100#endif // ENABLE(DFG_JIT)
101
102
103