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 
Run()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 v8::internal
56