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
8namespace v8 {
9namespace internal {
10
11void 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