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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/hydrogen-canonicalize.h" | |
6 #include "src/hydrogen-redundant-phi.h" | |
7 | |
8 namespace v8 { | |
9 namespace internal { | |
10 | |
11 void HCanonicalizePhase::Run() { | |
12 const ZoneList<HBasicBlock*>* blocks(graph()->blocks()); | |
13 // Before removing no-op instructions, save their semantic value. | |
14 // We must be careful not to set the flag unnecessarily, because GVN | |
15 // cannot identify two instructions when their flag value differs. | |
16 for (int i = 0; i < blocks->length(); ++i) { | |
17 for (HInstructionIterator it(blocks->at(i)); !it.Done(); it.Advance()) { | |
18 HInstruction* instr = it.Current(); | |
19 if (instr->IsArithmeticBinaryOperation()) { | |
20 if (instr->representation().IsInteger32()) { | |
21 if (instr->HasAtLeastOneUseWithFlagAndNoneWithout( | |
22 HInstruction::kTruncatingToInt32)) { | |
23 instr->SetFlag(HInstruction::kAllUsesTruncatingToInt32); | |
24 } | |
25 } else if (instr->representation().IsSmi()) { | |
26 if (instr->HasAtLeastOneUseWithFlagAndNoneWithout( | |
27 HInstruction::kTruncatingToSmi)) { | |
28 instr->SetFlag(HInstruction::kAllUsesTruncatingToSmi); | |
29 } else if (instr->HasAtLeastOneUseWithFlagAndNoneWithout( | |
30 HInstruction::kTruncatingToInt32)) { | |
31 // Avoid redundant minus zero check | |
32 instr->SetFlag(HInstruction::kAllUsesTruncatingToInt32); | |
33 } | |
34 } | |
35 } | |
36 } | |
37 } | |
38 | |
39 // Perform actual Canonicalization pass. | |
40 HRedundantPhiEliminationPhase redundant_phi_eliminator(graph()); | |
41 for (int i = 0; i < blocks->length(); ++i) { | |
42 // Eliminate redundant phis in the block first; changes to their inputs | |
43 // might have made them redundant, and eliminating them creates more | |
44 // opportunities for constant folding and strength reduction. | |
45 redundant_phi_eliminator.ProcessBlock(blocks->at(i)); | |
46 // Now canonicalize each instruction. | |
47 for (HInstructionIterator it(blocks->at(i)); !it.Done(); it.Advance()) { | |
48 HInstruction* instr = it.Current(); | |
49 HValue* value = instr->Canonicalize(); | |
50 if (value != instr) instr->DeleteAndReplaceWith(value); | |
51 } | |
52 } | |
53 } | |
54 | |
55 } // namespace internal | |
56 } // namespace v8 | |
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