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Issue 717473002: [turbofan] Fix select lowering. (Closed) Base URL: https://v8.googlecode.com/svn/branches/bleeding_edge
Patch Set: Added TODO. REBASE Created 6 years, 1 month ago
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1 // Copyright 2014 the V8 project authors. All rights reserved. 1 // Copyright 2014 the V8 project authors. All rights reserved.
2 // Use of this source code is governed by a BSD-style license that can be 2 // Use of this source code is governed by a BSD-style license that can be
3 // found in the LICENSE file. 3 // found in the LICENSE file.
4 4
5 #include "src/compiler/select-lowering.h" 5 #include "src/compiler/select-lowering.h"
6 6
7 #include "src/compiler/common-operator.h" 7 #include "src/compiler/common-operator.h"
8 #include "src/compiler/diamond.h" 8 #include "src/compiler/diamond.h"
9 #include "src/compiler/generic-node-inl.h" 9 #include "src/compiler/generic-node-inl.h"
10 #include "src/compiler/graph.h" 10 #include "src/compiler/graph.h"
11 11
12 namespace v8 { 12 namespace v8 {
13 namespace internal { 13 namespace internal {
14 namespace compiler { 14 namespace compiler {
15 15
16 SelectLowering::SelectLowering(Graph* graph, CommonOperatorBuilder* common) 16 SelectLowering::SelectLowering(Graph* graph, CommonOperatorBuilder* common)
17 : common_(common), 17 : common_(common),
18 graph_(graph), 18 graph_(graph),
19 merges_(Merges::key_compare(), Merges::allocator_type(graph->zone())) {} 19 merges_(Merges::key_compare(), Merges::allocator_type(graph->zone())) {}
20 20
21 21
22 SelectLowering::~SelectLowering() {} 22 SelectLowering::~SelectLowering() {}
23 23
24 24
25 Reduction SelectLowering::Reduce(Node* node) { 25 Reduction SelectLowering::Reduce(Node* node) {
26 if (node->opcode() != IrOpcode::kSelect) return NoChange(); 26 if (node->opcode() != IrOpcode::kSelect) return NoChange();
27 SelectParameters const p = SelectParametersOf(node->op()); 27 SelectParameters const p = SelectParametersOf(node->op());
28 28
29 Node* const cond = node->InputAt(0); 29 Node* cond = node->InputAt(0);
30 Node* vthen = node->InputAt(1);
31 Node* velse = node->InputAt(2);
32 Node* merge = nullptr;
30 33
31 // Check if we already have a diamond for this condition. 34 // Check if we already have a diamond for this condition.
32 auto i = merges_.find(cond); 35 auto range = merges_.equal_range(cond);
33 if (i == merges_.end()) { 36 for (auto i = range.first;; ++i) {
34 // Create a new diamond for this condition and remember its merge node. 37 if (i == range.second) {
35 Diamond d(graph(), common(), cond, p.hint()); 38 // Create a new diamond for this condition and remember its merge node.
36 i = merges_.insert(std::make_pair(cond, d.merge)).first; 39 Diamond d(graph(), common(), cond, p.hint());
40 merges_.insert(std::make_pair(cond, d.merge));
41 merge = d.merge;
42 break;
43 }
44
45 // If the diamond is reachable from the Select, merging them would result in
46 // an unschedulable graph, so we cannot reuse the diamond in that case.
47 merge = i->second;
48 if (!ReachableFrom(merge, node)) {
49 break;
50 }
37 } 51 }
38 52
39 DCHECK_EQ(cond, i->first);
40
41 // Create a Phi hanging off the previously determined merge. 53 // Create a Phi hanging off the previously determined merge.
42 node->set_op(common()->Phi(p.type(), 2)); 54 node->set_op(common()->Phi(p.type(), 2));
43 node->ReplaceInput(0, node->InputAt(1)); 55 node->ReplaceInput(0, vthen);
44 node->ReplaceInput(1, node->InputAt(2)); 56 node->ReplaceInput(1, velse);
45 node->ReplaceInput(2, i->second); 57 node->ReplaceInput(2, merge);
46 return Changed(node); 58 return Changed(node);
47 } 59 }
48 60
61
62 bool SelectLowering::ReachableFrom(Node* const sink, Node* const source) {
63 // TODO(turbofan): This is probably horribly expensive, and it should be moved
64 // into node.h or somewhere else?!
65 Zone zone(graph()->zone()->isolate());
66 std::queue<Node*, NodeDeque> pending((NodeDeque(&zone)));
67 BoolVector visited(graph()->NodeCount(), false, &zone);
68 pending.push(source);
69 while (!pending.empty()) {
70 Node* current = pending.front();
71 if (current == sink) return true;
72 pending.pop();
73 visited[current->id()] = true;
74 for (auto input : current->inputs()) {
75 if (!visited[input->id()]) pending.push(input);
76 }
77 }
78 return false;
79 }
80
49 } // namespace compiler 81 } // namespace compiler
50 } // namespace internal 82 } // namespace internal
51 } // namespace v8 83 } // namespace v8
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