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
3 // found in the LICENSE file.
4 
5 #ifndef V8_COMPILER_PHI_REDUCER_H_
6 #define V8_COMPILER_PHI_REDUCER_H_
7 
8 #include "src/compiler/graph-reducer.h"
9 
10 namespace v8 {
11 namespace internal {
12 namespace compiler {
13 
14 // Replaces redundant phis if all the inputs are the same or the phi itself.
15 class PhiReducer FINAL : public Reducer {
16  public:
Reduce(Node * node)17   virtual Reduction Reduce(Node* node) OVERRIDE {
18     if (node->opcode() != IrOpcode::kPhi &&
19         node->opcode() != IrOpcode::kEffectPhi)
20       return NoChange();
21 
22     int n = node->op()->InputCount();
23     if (n == 1) return Replace(node->InputAt(0));
24 
25     Node* replacement = NULL;
26     Node::Inputs inputs = node->inputs();
27     for (InputIter it = inputs.begin(); n > 0; --n, ++it) {
28       Node* input = *it;
29       if (input != node && input != replacement) {
30         if (replacement != NULL) return NoChange();
31         replacement = input;
32       }
33     }
34     DCHECK_NE(node, replacement);
35     return Replace(replacement);
36   }
37 };
38 }
39 }
40 }  // namespace v8::internal::compiler
41 
42 #endif  // V8_COMPILER_PHI_REDUCER_H_
43