1 // Copyright 2015 the V8 project authors. All rights reserved.
2 // Use of this source code is governed by a BSD-style license that can be
3 // found in the LICENSE file.
4 
5 #include "src/compiler/graph-trimmer.h"
6 
7 #include "src/compiler/graph.h"
8 
9 namespace v8 {
10 namespace internal {
11 namespace compiler {
12 
GraphTrimmer(Zone * zone,Graph * graph)13 GraphTrimmer::GraphTrimmer(Zone* zone, Graph* graph)
14     : graph_(graph), is_live_(graph, 2), live_(zone) {
15   live_.reserve(graph->NodeCount());
16 }
17 
18 
19 GraphTrimmer::~GraphTrimmer() = default;
20 
21 
TrimGraph()22 void GraphTrimmer::TrimGraph() {
23   // Mark end node as live.
24   MarkAsLive(graph()->end());
25   // Compute transitive closure of live nodes.
26   for (size_t i = 0; i < live_.size(); ++i) {
27     Node* const live = live_[i];
28     for (Node* const input : live->inputs()) MarkAsLive(input);
29   }
30   // Remove dead->live edges.
31   for (Node* const live : live_) {
32     DCHECK(IsLive(live));
33     for (Edge edge : live->use_edges()) {
34       Node* const user = edge.from();
35       if (!IsLive(user)) {
36         if (FLAG_trace_turbo_trimming) {
37           StdoutStream{} << "DeadLink: " << *user << "(" << edge.index()
38                          << ") -> " << *live << std::endl;
39         }
40         edge.UpdateTo(nullptr);
41       }
42     }
43   }
44 }
45 
46 }  // namespace compiler
47 }  // namespace internal
48 }  // namespace v8
49