1/*
2 * Copyright (C) 2014 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 "DFGStaticExecutionCountEstimationPhase.h"
28
29#if ENABLE(DFG_JIT)
30
31#include "DFGBasicBlockInlines.h"
32#include "DFGGraph.h"
33#include "DFGPhase.h"
34#include "JSCInlines.h"
35
36namespace JSC { namespace DFG {
37
38class StaticExecutionCountEstimationPhase : public Phase {
39public:
40    StaticExecutionCountEstimationPhase(Graph& graph)
41        : Phase(graph, "static execution count estimation")
42    {
43    }
44
45    bool run()
46    {
47        m_graph.m_naturalLoops.computeIfNecessary(m_graph);
48
49        // Estimate basic block execution counts based on loop depth.
50        for (BlockIndex blockIndex = m_graph.numBlocks(); blockIndex--;) {
51            BasicBlock* block = m_graph.block(blockIndex);
52            if (!block)
53                continue;
54
55            block->executionCount = pow(10, m_graph.m_naturalLoops.loopDepth(block));
56        }
57
58        // Estimate branch weights based on execution counts. This isn't quite correct. It'll
59        // assume that each block's conditional successor only has that block as its
60        // predecessor.
61        for (BlockIndex blockIndex = m_graph.numBlocks(); blockIndex--;) {
62            BasicBlock* block = m_graph.block(blockIndex);
63            if (!block)
64                continue;
65
66            switch (block->last()->op()) {
67            case Branch: {
68                BranchData* data = block->last()->branchData();
69                applyCounts(data->taken);
70                applyCounts(data->notTaken);
71                break;
72            }
73
74            case Switch: {
75                SwitchData* data = block->last()->switchData();
76                for (unsigned i = data->cases.size(); i--;)
77                    applyCounts(data->cases[i].target);
78                applyCounts(data->fallThrough);
79                break;
80            }
81
82            default:
83                break;
84            }
85        }
86
87        return true;
88    }
89
90private:
91    void applyCounts(BranchTarget& target)
92    {
93        target.count = target.block->executionCount;
94    }
95};
96
97bool performStaticExecutionCountEstimation(Graph& graph)
98{
99    SamplingRegion samplingRegion("DFG Static Execution Count Estimation");
100    return runPhase<StaticExecutionCountEstimationPhase>(graph);
101}
102
103} } // namespace JSC::DFG
104
105#endif // ENABLE(DFG_JIT)
106
107
108