1 // Copyright 2013 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/crankshaft/hydrogen-dehoist.h"
6 
7 #include "src/base/safe_math.h"
8 
9 namespace v8 {
10 namespace internal {
11 
DehoistArrayIndex(ArrayInstructionInterface * array_operation)12 static void DehoistArrayIndex(ArrayInstructionInterface* array_operation) {
13   HValue* index = array_operation->GetKey()->ActualValue();
14   if (!index->representation().IsSmiOrInteger32()) return;
15   if (!index->IsAdd() && !index->IsSub()) return;
16 
17   HConstant* constant;
18   HValue* subexpression;
19   HBinaryOperation* binary_operation = HBinaryOperation::cast(index);
20   if (binary_operation->left()->IsConstant() && index->IsAdd()) {
21     subexpression = binary_operation->right();
22     constant = HConstant::cast(binary_operation->left());
23   } else if (binary_operation->right()->IsConstant()) {
24     subexpression = binary_operation->left();
25     constant = HConstant::cast(binary_operation->right());
26   } else {
27     return;
28   }
29 
30   if (!constant->HasInteger32Value()) return;
31   v8::base::internal::CheckedNumeric<int32_t> checked_value =
32       constant->Integer32Value();
33   int32_t sign = binary_operation->IsSub() ? -1 : 1;
34   checked_value = checked_value * sign;
35 
36   // Multiply value by elements size, bailing out on overflow.
37   int32_t elements_kind_size =
38       1 << ElementsKindToShiftSize(array_operation->elements_kind());
39   checked_value = checked_value * elements_kind_size;
40   if (!checked_value.IsValid()) return;
41   int32_t value = checked_value.ValueOrDie();
42   if (value < 0) return;
43 
44   // Ensure that the array operation can add value to existing base offset
45   // without overflowing.
46   if (!array_operation->TryIncreaseBaseOffset(value)) return;
47 
48   array_operation->SetKey(subexpression);
49   if (binary_operation->HasNoUses()) {
50     binary_operation->DeleteAndReplaceWith(NULL);
51   }
52 
53   array_operation->SetDehoisted(true);
54 }
55 
56 
Run()57 void HDehoistIndexComputationsPhase::Run() {
58   const ZoneList<HBasicBlock*>* blocks(graph()->blocks());
59   for (int i = 0; i < blocks->length(); ++i) {
60     for (HInstructionIterator it(blocks->at(i)); !it.Done(); it.Advance()) {
61       HInstruction* instr = it.Current();
62       if (instr->IsLoadKeyed()) {
63         DehoistArrayIndex(HLoadKeyed::cast(instr));
64       } else if (instr->IsStoreKeyed()) {
65         DehoistArrayIndex(HStoreKeyed::cast(instr));
66       }
67     }
68   }
69 }
70 
71 }  // namespace internal
72 }  // namespace v8
73