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-canonicalize.h"
6 
7 #include "src/counters.h"
8 #include "src/crankshaft/hydrogen-redundant-phi.h"
9 #include "src/objects-inl.h"
10 
11 namespace v8 {
12 namespace internal {
13 
Run()14 void HCanonicalizePhase::Run() {
15   const ZoneList<HBasicBlock*>* blocks(graph()->blocks());
16   // Before removing no-op instructions, save their semantic value.
17   // We must be careful not to set the flag unnecessarily, because GVN
18   // cannot identify two instructions when their flag value differs.
19   for (int i = 0; i < blocks->length(); ++i) {
20     for (HInstructionIterator it(blocks->at(i)); !it.Done(); it.Advance()) {
21       HInstruction* instr = it.Current();
22       if (instr->IsArithmeticBinaryOperation()) {
23         if (instr->representation().IsInteger32()) {
24           if (instr->HasAtLeastOneUseWithFlagAndNoneWithout(
25                   HInstruction::kTruncatingToInt32)) {
26             instr->SetFlag(HInstruction::kAllUsesTruncatingToInt32);
27           }
28         } else if (instr->representation().IsSmi()) {
29           if (instr->HasAtLeastOneUseWithFlagAndNoneWithout(
30                   HInstruction::kTruncatingToSmi)) {
31             instr->SetFlag(HInstruction::kAllUsesTruncatingToSmi);
32           } else if (instr->HasAtLeastOneUseWithFlagAndNoneWithout(
33                          HInstruction::kTruncatingToInt32)) {
34             // Avoid redundant minus zero check
35             instr->SetFlag(HInstruction::kAllUsesTruncatingToInt32);
36           }
37         }
38       }
39     }
40   }
41 
42   // Perform actual Canonicalization pass.
43   HRedundantPhiEliminationPhase redundant_phi_eliminator(graph());
44   for (int i = 0; i < blocks->length(); ++i) {
45     // Eliminate redundant phis in the block first; changes to their inputs
46     // might have made them redundant, and eliminating them creates more
47     // opportunities for constant folding and strength reduction.
48     redundant_phi_eliminator.ProcessBlock(blocks->at(i));
49     // Now canonicalize each instruction.
50     for (HInstructionIterator it(blocks->at(i)); !it.Done(); it.Advance()) {
51       HInstruction* instr = it.Current();
52       HValue* value = instr->Canonicalize();
53       if (value != instr) instr->DeleteAndReplaceWith(value);
54     }
55   }
56 }
57 
58 }  // namespace internal
59 }  // namespace v8
60