summaryrefslogtreecommitdiffstats
path: root/devtools/shared/heapsnapshot/DominatorTree.cpp
blob: e78aad43d259e9ee6b9e20e25001fe71f2ab35e8 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2; -*- */
/* This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this
 * file, You can obtain one at http://mozilla.org/MPL/2.0/. */

#include "mozilla/devtools/DominatorTree.h"
#include "mozilla/dom/DominatorTreeBinding.h"
#include "mozilla/ErrorResult.h"

namespace mozilla {
namespace devtools {

dom::Nullable<uint64_t> DominatorTree::GetRetainedSize(uint64_t aNodeId,
                                                       ErrorResult& aRv) {
  JS::ubi::Node::Id id(aNodeId);
  auto node = mHeapSnapshot->getNodeById(id);
  if (node.isNothing()) return dom::Nullable<uint64_t>();

  auto mallocSizeOf = GetCurrentThreadDebuggerMallocSizeOf();
  JS::ubi::Node::Size size = 0;
  if (!mDominatorTree.getRetainedSize(*node, mallocSizeOf, size)) {
    aRv.Throw(NS_ERROR_OUT_OF_MEMORY);
    return dom::Nullable<uint64_t>();
  }

  MOZ_ASSERT(size != 0,
             "The node should not have been unknown since we got it from the "
             "heap snapshot.");
  return dom::Nullable<uint64_t>(size);
}

struct NodeAndRetainedSize {
  JS::ubi::Node mNode;
  JS::ubi::Node::Size mSize;

  NodeAndRetainedSize(const JS::ubi::Node& aNode, JS::ubi::Node::Size aSize)
      : mNode(aNode), mSize(aSize) {}

  struct Comparator {
    static bool Equals(const NodeAndRetainedSize& aLhs,
                       const NodeAndRetainedSize& aRhs) {
      return aLhs.mSize == aRhs.mSize;
    }

    static bool LessThan(const NodeAndRetainedSize& aLhs,
                         const NodeAndRetainedSize& aRhs) {
      // Use > because we want to sort from greatest to least retained size.
      return aLhs.mSize > aRhs.mSize;
    }
  };
};

void DominatorTree::GetImmediatelyDominated(
    uint64_t aNodeId, dom::Nullable<nsTArray<uint64_t>>& aOutResult,
    ErrorResult& aRv) {
  MOZ_ASSERT(aOutResult.IsNull());

  JS::ubi::Node::Id id(aNodeId);
  Maybe<JS::ubi::Node> node = mHeapSnapshot->getNodeById(id);
  if (node.isNothing()) return;

  // Get all immediately dominated nodes and their retained sizes.
  MallocSizeOf mallocSizeOf = GetCurrentThreadDebuggerMallocSizeOf();
  Maybe<JS::ubi::DominatorTree::DominatedSetRange> range =
      mDominatorTree.getDominatedSet(*node);
  MOZ_ASSERT(
      range.isSome(),
      "The node should be known, since we got it from the heap snapshot.");
  size_t length = range->length();
  nsTArray<NodeAndRetainedSize> dominatedNodes(length);
  for (const JS::ubi::Node& dominatedNode : *range) {
    JS::ubi::Node::Size retainedSize = 0;
    if (NS_WARN_IF(!mDominatorTree.getRetainedSize(dominatedNode, mallocSizeOf,
                                                   retainedSize))) {
      aRv.Throw(NS_ERROR_OUT_OF_MEMORY);
      return;
    }
    MOZ_ASSERT(retainedSize != 0,
               "retainedSize should not be zero since we know the node is in "
               "the dominator tree.");

    dominatedNodes.AppendElement(
        NodeAndRetainedSize(dominatedNode, retainedSize));
  }

  // Sort them by retained size.
  NodeAndRetainedSize::Comparator comparator;
  dominatedNodes.Sort(comparator);

  // Fill the result with the nodes' ids.
  JS::ubi::Node root = mDominatorTree.root();
  aOutResult.SetValue(nsTArray<uint64_t>(length));
  for (const NodeAndRetainedSize& entry : dominatedNodes) {
    // The root dominates itself, but we don't want to expose that to JS.
    if (entry.mNode == root) continue;

    aOutResult.Value().AppendElement(entry.mNode.identifier());
  }
}

dom::Nullable<uint64_t> DominatorTree::GetImmediateDominator(
    uint64_t aNodeId) const {
  JS::ubi::Node::Id id(aNodeId);
  Maybe<JS::ubi::Node> node = mHeapSnapshot->getNodeById(id);
  if (node.isNothing()) return dom::Nullable<uint64_t>();

  JS::ubi::Node dominator = mDominatorTree.getImmediateDominator(*node);
  if (!dominator || dominator == *node) return dom::Nullable<uint64_t>();

  return dom::Nullable<uint64_t>(dominator.identifier());
}

/*** Cycle Collection Boilerplate
 * *****************************************************************/

NS_IMPL_CYCLE_COLLECTION_WRAPPERCACHE(DominatorTree, mParent, mHeapSnapshot)

NS_IMPL_CYCLE_COLLECTING_ADDREF(DominatorTree)
NS_IMPL_CYCLE_COLLECTING_RELEASE(DominatorTree)

NS_INTERFACE_MAP_BEGIN_CYCLE_COLLECTION(DominatorTree)
  NS_WRAPPERCACHE_INTERFACE_MAP_ENTRY
  NS_INTERFACE_MAP_ENTRY(nsISupports)
NS_INTERFACE_MAP_END

/* virtual */
JSObject* DominatorTree::WrapObject(JSContext* aCx,
                                    JS::HandleObject aGivenProto) {
  return dom::DominatorTree_Binding::Wrap(aCx, this, aGivenProto);
}

}  // namespace devtools
}  // namespace mozilla