1// Copyright 2013 the V8 project authors. All rights reserved.
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3// modification, are permitted provided that the following conditions are
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27
28#include "hydrogen-dehoist.h"
29
30namespace v8 {
31namespace internal {
32
33static void DehoistArrayIndex(ArrayInstructionInterface* array_operation) {
34  HValue* index = array_operation->GetKey()->ActualValue();
35  if (!index->representation().IsSmiOrInteger32()) return;
36  if (!index->IsAdd() && !index->IsSub()) return;
37
38  HConstant* constant;
39  HValue* subexpression;
40  HBinaryOperation* binary_operation = HBinaryOperation::cast(index);
41  if (binary_operation->left()->IsConstant() && index->IsAdd()) {
42    subexpression = binary_operation->right();
43    constant = HConstant::cast(binary_operation->left());
44  } else if (binary_operation->right()->IsConstant()) {
45    subexpression = binary_operation->left();
46    constant = HConstant::cast(binary_operation->right());
47  } else {
48    return;
49  }
50
51  if (!constant->HasInteger32Value()) return;
52  int32_t sign = binary_operation->IsSub() ? -1 : 1;
53  int32_t value = constant->Integer32Value() * sign;
54  // We limit offset values to 30 bits because we want to avoid the risk of
55  // overflows when the offset is added to the object header size.
56  if (value >= 1 << 30 || value < 0) return;
57  array_operation->SetKey(subexpression);
58  if (binary_operation->HasNoUses()) {
59    binary_operation->DeleteAndReplaceWith(NULL);
60  }
61  array_operation->SetIndexOffset(static_cast<uint32_t>(value));
62  array_operation->SetDehoisted(true);
63}
64
65
66void HDehoistIndexComputationsPhase::Run() {
67  const ZoneList<HBasicBlock*>* blocks(graph()->blocks());
68  for (int i = 0; i < blocks->length(); ++i) {
69    for (HInstructionIterator it(blocks->at(i)); !it.Done(); it.Advance()) {
70      HInstruction* instr = it.Current();
71      if (instr->IsLoadKeyed()) {
72        DehoistArrayIndex(HLoadKeyed::cast(instr));
73      } else if (instr->IsStoreKeyed()) {
74        DehoistArrayIndex(HStoreKeyed::cast(instr));
75      }
76    }
77  }
78}
79
80} }  // namespace v8::internal
81