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annotate lib/IR/Dominators.cpp @ 33:e4204d083e25 LLVM3.5

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LLVM 3.5
author Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp>
date Thu, 12 Dec 2013 14:32:10 +0900
parents 95c75e76d11b
children 54457678186b
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1 //===- Dominators.cpp - Dominator Calculation -----------------------------===//
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2 //
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3 // The LLVM Compiler Infrastructure
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4 //
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5 // This file is distributed under the University of Illinois Open Source
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6 // License. See LICENSE.TXT for details.
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7 //
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8 //===----------------------------------------------------------------------===//
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9 //
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10 // This file implements simple dominator construction algorithms for finding
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11 // forward dominators. Postdominators are available in libanalysis, but are not
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12 // included in libvmcore, because it's not needed. Forward dominators are
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13 // needed to support the Verifier pass.
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14 //
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15 //===----------------------------------------------------------------------===//
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16
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17 #include "llvm/Analysis/Dominators.h"
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18 #include "llvm/ADT/DepthFirstIterator.h"
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19 #include "llvm/ADT/SmallPtrSet.h"
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20 #include "llvm/ADT/SmallVector.h"
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21 #include "llvm/Analysis/DominatorInternals.h"
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22 #include "llvm/Assembly/Writer.h"
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23 #include "llvm/IR/Instructions.h"
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24 #include "llvm/Support/CFG.h"
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25 #include "llvm/Support/CommandLine.h"
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26 #include "llvm/Support/Compiler.h"
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27 #include "llvm/Support/Debug.h"
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28 #include "llvm/Support/raw_ostream.h"
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29 #include <algorithm>
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30 using namespace llvm;
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31
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32 // Always verify dominfo if expensive checking is enabled.
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33 #ifdef XDEBUG
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34 static bool VerifyDomInfo = true;
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35 #else
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36 static bool VerifyDomInfo = false;
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37 #endif
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38 static cl::opt<bool,true>
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39 VerifyDomInfoX("verify-dom-info", cl::location(VerifyDomInfo),
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40 cl::desc("Verify dominator info (time consuming)"));
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41
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42 bool BasicBlockEdge::isSingleEdge() const {
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43 const TerminatorInst *TI = Start->getTerminator();
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44 unsigned NumEdgesToEnd = 0;
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45 for (unsigned int i = 0, n = TI->getNumSuccessors(); i < n; ++i) {
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46 if (TI->getSuccessor(i) == End)
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47 ++NumEdgesToEnd;
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48 if (NumEdgesToEnd >= 2)
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49 return false;
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50 }
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51 assert(NumEdgesToEnd == 1);
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52 return true;
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53 }
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54
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55 //===----------------------------------------------------------------------===//
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56 // DominatorTree Implementation
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57 //===----------------------------------------------------------------------===//
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58 //
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59 // Provide public access to DominatorTree information. Implementation details
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60 // can be found in DominatorInternals.h.
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61 //
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62 //===----------------------------------------------------------------------===//
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63
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64 TEMPLATE_INSTANTIATION(class llvm::DomTreeNodeBase<BasicBlock>);
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65 TEMPLATE_INSTANTIATION(class llvm::DominatorTreeBase<BasicBlock>);
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66
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67 char DominatorTree::ID = 0;
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68 INITIALIZE_PASS(DominatorTree, "domtree",
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69 "Dominator Tree Construction", true, true)
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70
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71 bool DominatorTree::runOnFunction(Function &F) {
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72 DT->recalculate(F);
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73 return false;
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74 }
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75
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76 void DominatorTree::verifyAnalysis() const {
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77 if (!VerifyDomInfo) return;
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78
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79 Function &F = *getRoot()->getParent();
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80
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81 DominatorTree OtherDT;
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82 OtherDT.getBase().recalculate(F);
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83 if (compare(OtherDT)) {
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84 errs() << "DominatorTree is not up to date!\nComputed:\n";
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85 print(errs());
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86 errs() << "\nActual:\n";
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87 OtherDT.print(errs());
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88 abort();
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89 }
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90 }
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91
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92 void DominatorTree::print(raw_ostream &OS, const Module *) const {
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93 DT->print(OS);
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94 }
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95
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96 // dominates - Return true if Def dominates a use in User. This performs
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97 // the special checks necessary if Def and User are in the same basic block.
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98 // Note that Def doesn't dominate a use in Def itself!
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99 bool DominatorTree::dominates(const Instruction *Def,
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100 const Instruction *User) const {
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101 const BasicBlock *UseBB = User->getParent();
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102 const BasicBlock *DefBB = Def->getParent();
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103
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104 // Any unreachable use is dominated, even if Def == User.
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105 if (!isReachableFromEntry(UseBB))
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106 return true;
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107
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108 // Unreachable definitions don't dominate anything.
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109 if (!isReachableFromEntry(DefBB))
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110 return false;
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111
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112 // An instruction doesn't dominate a use in itself.
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113 if (Def == User)
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114 return false;
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115
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116 // The value defined by an invoke dominates an instruction only if
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117 // it dominates every instruction in UseBB.
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118 // A PHI is dominated only if the instruction dominates every possible use
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119 // in the UseBB.
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120 if (isa<InvokeInst>(Def) || isa<PHINode>(User))
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121 return dominates(Def, UseBB);
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122
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123 if (DefBB != UseBB)
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124 return dominates(DefBB, UseBB);
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125
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126 // Loop through the basic block until we find Def or User.
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127 BasicBlock::const_iterator I = DefBB->begin();
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128 for (; &*I != Def && &*I != User; ++I)
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129 /*empty*/;
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130
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131 return &*I == Def;
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Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp>
parents:
diff changeset
132 }
95c75e76d11b LLVM 3.4
Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp>
parents:
diff changeset
133
95c75e76d11b LLVM 3.4
Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp>
parents:
diff changeset
134 // true if Def would dominate a use in any instruction in UseBB.
95c75e76d11b LLVM 3.4
Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp>
parents:
diff changeset
135 // note that dominates(Def, Def->getParent()) is false.
95c75e76d11b LLVM 3.4
Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp>
parents:
diff changeset
136 bool DominatorTree::dominates(const Instruction *Def,
95c75e76d11b LLVM 3.4
Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp>
parents:
diff changeset
137 const BasicBlock *UseBB) const {
95c75e76d11b LLVM 3.4
Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp>
parents:
diff changeset
138 const BasicBlock *DefBB = Def->getParent();
95c75e76d11b LLVM 3.4
Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp>
parents:
diff changeset
139
95c75e76d11b LLVM 3.4
Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp>
parents:
diff changeset
140 // Any unreachable use is dominated, even if DefBB == UseBB.
95c75e76d11b LLVM 3.4
Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp>
parents:
diff changeset
141 if (!isReachableFromEntry(UseBB))
95c75e76d11b LLVM 3.4
Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp>
parents:
diff changeset
142 return true;
95c75e76d11b LLVM 3.4
Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp>
parents:
diff changeset
143
95c75e76d11b LLVM 3.4
Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp>
parents:
diff changeset
144 // Unreachable definitions don't dominate anything.
95c75e76d11b LLVM 3.4
Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp>
parents:
diff changeset
145 if (!isReachableFromEntry(DefBB))
95c75e76d11b LLVM 3.4
Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp>
parents:
diff changeset
146 return false;
95c75e76d11b LLVM 3.4
Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp>
parents:
diff changeset
147
95c75e76d11b LLVM 3.4
Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp>
parents:
diff changeset
148 if (DefBB == UseBB)
95c75e76d11b LLVM 3.4
Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp>
parents:
diff changeset
149 return false;
95c75e76d11b LLVM 3.4
Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp>
parents:
diff changeset
150
95c75e76d11b LLVM 3.4
Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp>
parents:
diff changeset
151 const InvokeInst *II = dyn_cast<InvokeInst>(Def);
95c75e76d11b LLVM 3.4
Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp>
parents:
diff changeset
152 if (!II)
95c75e76d11b LLVM 3.4
Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp>
parents:
diff changeset
153 return dominates(DefBB, UseBB);
95c75e76d11b LLVM 3.4
Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp>
parents:
diff changeset
154
95c75e76d11b LLVM 3.4
Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp>
parents:
diff changeset
155 // Invoke results are only usable in the normal destination, not in the
95c75e76d11b LLVM 3.4
Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp>
parents:
diff changeset
156 // exceptional destination.
95c75e76d11b LLVM 3.4
Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp>
parents:
diff changeset
157 BasicBlock *NormalDest = II->getNormalDest();
95c75e76d11b LLVM 3.4
Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp>
parents:
diff changeset
158 BasicBlockEdge E(DefBB, NormalDest);
95c75e76d11b LLVM 3.4
Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp>
parents:
diff changeset
159 return dominates(E, UseBB);
95c75e76d11b LLVM 3.4
Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp>
parents:
diff changeset
160 }
95c75e76d11b LLVM 3.4
Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp>
parents:
diff changeset
161
95c75e76d11b LLVM 3.4
Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp>
parents:
diff changeset
162 bool DominatorTree::dominates(const BasicBlockEdge &BBE,
95c75e76d11b LLVM 3.4
Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp>
parents:
diff changeset
163 const BasicBlock *UseBB) const {
95c75e76d11b LLVM 3.4
Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp>
parents:
diff changeset
164 // Assert that we have a single edge. We could handle them by simply
95c75e76d11b LLVM 3.4
Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp>
parents:
diff changeset
165 // returning false, but since isSingleEdge is linear on the number of
95c75e76d11b LLVM 3.4
Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp>
parents:
diff changeset
166 // edges, the callers can normally handle them more efficiently.
95c75e76d11b LLVM 3.4
Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp>
parents:
diff changeset
167 assert(BBE.isSingleEdge());
95c75e76d11b LLVM 3.4
Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp>
parents:
diff changeset
168
95c75e76d11b LLVM 3.4
Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp>
parents:
diff changeset
169 // If the BB the edge ends in doesn't dominate the use BB, then the
95c75e76d11b LLVM 3.4
Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp>
parents:
diff changeset
170 // edge also doesn't.
95c75e76d11b LLVM 3.4
Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp>
parents:
diff changeset
171 const BasicBlock *Start = BBE.getStart();
95c75e76d11b LLVM 3.4
Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp>
parents:
diff changeset
172 const BasicBlock *End = BBE.getEnd();
95c75e76d11b LLVM 3.4
Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp>
parents:
diff changeset
173 if (!dominates(End, UseBB))
95c75e76d11b LLVM 3.4
Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp>
parents:
diff changeset
174 return false;
95c75e76d11b LLVM 3.4
Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp>
parents:
diff changeset
175
95c75e76d11b LLVM 3.4
Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp>
parents:
diff changeset
176 // Simple case: if the end BB has a single predecessor, the fact that it
95c75e76d11b LLVM 3.4
Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp>
parents:
diff changeset
177 // dominates the use block implies that the edge also does.
95c75e76d11b LLVM 3.4
Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp>
parents:
diff changeset
178 if (End->getSinglePredecessor())
95c75e76d11b LLVM 3.4
Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp>
parents:
diff changeset
179 return true;
95c75e76d11b LLVM 3.4
Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp>
parents:
diff changeset
180
95c75e76d11b LLVM 3.4
Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp>
parents:
diff changeset
181 // The normal edge from the invoke is critical. Conceptually, what we would
95c75e76d11b LLVM 3.4
Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp>
parents:
diff changeset
182 // like to do is split it and check if the new block dominates the use.
95c75e76d11b LLVM 3.4
Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp>
parents:
diff changeset
183 // With X being the new block, the graph would look like:
95c75e76d11b LLVM 3.4
Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp>
parents:
diff changeset
184 //
95c75e76d11b LLVM 3.4
Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp>
parents:
diff changeset
185 // DefBB
95c75e76d11b LLVM 3.4
Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp>
parents:
diff changeset
186 // /\ . .
95c75e76d11b LLVM 3.4
Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp>
parents:
diff changeset
187 // / \ . .
95c75e76d11b LLVM 3.4
Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp>
parents:
diff changeset
188 // / \ . .
95c75e76d11b LLVM 3.4
Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp>
parents:
diff changeset
189 // / \ | |
95c75e76d11b LLVM 3.4
Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp>
parents:
diff changeset
190 // A X B C
95c75e76d11b LLVM 3.4
Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp>
parents:
diff changeset
191 // | \ | /
95c75e76d11b LLVM 3.4
Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp>
parents:
diff changeset
192 // . \|/
95c75e76d11b LLVM 3.4
Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp>
parents:
diff changeset
193 // . NormalDest
95c75e76d11b LLVM 3.4
Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp>
parents:
diff changeset
194 // .
95c75e76d11b LLVM 3.4
Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp>
parents:
diff changeset
195 //
95c75e76d11b LLVM 3.4
Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp>
parents:
diff changeset
196 // Given the definition of dominance, NormalDest is dominated by X iff X
95c75e76d11b LLVM 3.4
Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp>
parents:
diff changeset
197 // dominates all of NormalDest's predecessors (X, B, C in the example). X
95c75e76d11b LLVM 3.4
Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp>
parents:
diff changeset
198 // trivially dominates itself, so we only have to find if it dominates the
95c75e76d11b LLVM 3.4
Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp>
parents:
diff changeset
199 // other predecessors. Since the only way out of X is via NormalDest, X can
95c75e76d11b LLVM 3.4
Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp>
parents:
diff changeset
200 // only properly dominate a node if NormalDest dominates that node too.
95c75e76d11b LLVM 3.4
Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp>
parents:
diff changeset
201 for (const_pred_iterator PI = pred_begin(End), E = pred_end(End);
95c75e76d11b LLVM 3.4
Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp>
parents:
diff changeset
202 PI != E; ++PI) {
95c75e76d11b LLVM 3.4
Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp>
parents:
diff changeset
203 const BasicBlock *BB = *PI;
95c75e76d11b LLVM 3.4
Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp>
parents:
diff changeset
204 if (BB == Start)
95c75e76d11b LLVM 3.4
Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp>
parents:
diff changeset
205 continue;
95c75e76d11b LLVM 3.4
Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp>
parents:
diff changeset
206
95c75e76d11b LLVM 3.4
Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp>
parents:
diff changeset
207 if (!dominates(End, BB))
95c75e76d11b LLVM 3.4
Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp>
parents:
diff changeset
208 return false;
95c75e76d11b LLVM 3.4
Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp>
parents:
diff changeset
209 }
95c75e76d11b LLVM 3.4
Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp>
parents:
diff changeset
210 return true;
95c75e76d11b LLVM 3.4
Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp>
parents:
diff changeset
211 }
95c75e76d11b LLVM 3.4
Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp>
parents:
diff changeset
212
95c75e76d11b LLVM 3.4
Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp>
parents:
diff changeset
213 bool DominatorTree::dominates(const BasicBlockEdge &BBE,
95c75e76d11b LLVM 3.4
Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp>
parents:
diff changeset
214 const Use &U) const {
95c75e76d11b LLVM 3.4
Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp>
parents:
diff changeset
215 // Assert that we have a single edge. We could handle them by simply
95c75e76d11b LLVM 3.4
Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp>
parents:
diff changeset
216 // returning false, but since isSingleEdge is linear on the number of
95c75e76d11b LLVM 3.4
Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp>
parents:
diff changeset
217 // edges, the callers can normally handle them more efficiently.
95c75e76d11b LLVM 3.4
Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp>
parents:
diff changeset
218 assert(BBE.isSingleEdge());
95c75e76d11b LLVM 3.4
Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp>
parents:
diff changeset
219
95c75e76d11b LLVM 3.4
Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp>
parents:
diff changeset
220 Instruction *UserInst = cast<Instruction>(U.getUser());
95c75e76d11b LLVM 3.4
Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp>
parents:
diff changeset
221 // A PHI in the end of the edge is dominated by it.
95c75e76d11b LLVM 3.4
Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp>
parents:
diff changeset
222 PHINode *PN = dyn_cast<PHINode>(UserInst);
95c75e76d11b LLVM 3.4
Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp>
parents:
diff changeset
223 if (PN && PN->getParent() == BBE.getEnd() &&
95c75e76d11b LLVM 3.4
Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp>
parents:
diff changeset
224 PN->getIncomingBlock(U) == BBE.getStart())
95c75e76d11b LLVM 3.4
Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp>
parents:
diff changeset
225 return true;
95c75e76d11b LLVM 3.4
Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp>
parents:
diff changeset
226
95c75e76d11b LLVM 3.4
Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp>
parents:
diff changeset
227 // Otherwise use the edge-dominates-block query, which
95c75e76d11b LLVM 3.4
Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp>
parents:
diff changeset
228 // handles the crazy critical edge cases properly.
95c75e76d11b LLVM 3.4
Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp>
parents:
diff changeset
229 const BasicBlock *UseBB;
95c75e76d11b LLVM 3.4
Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp>
parents:
diff changeset
230 if (PN)
95c75e76d11b LLVM 3.4
Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp>
parents:
diff changeset
231 UseBB = PN->getIncomingBlock(U);
95c75e76d11b LLVM 3.4
Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp>
parents:
diff changeset
232 else
95c75e76d11b LLVM 3.4
Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp>
parents:
diff changeset
233 UseBB = UserInst->getParent();
95c75e76d11b LLVM 3.4
Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp>
parents:
diff changeset
234 return dominates(BBE, UseBB);
95c75e76d11b LLVM 3.4
Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp>
parents:
diff changeset
235 }
95c75e76d11b LLVM 3.4
Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp>
parents:
diff changeset
236
95c75e76d11b LLVM 3.4
Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp>
parents:
diff changeset
237 bool DominatorTree::dominates(const Instruction *Def,
95c75e76d11b LLVM 3.4
Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp>
parents:
diff changeset
238 const Use &U) const {
95c75e76d11b LLVM 3.4
Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp>
parents:
diff changeset
239 Instruction *UserInst = cast<Instruction>(U.getUser());
95c75e76d11b LLVM 3.4
Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp>
parents:
diff changeset
240 const BasicBlock *DefBB = Def->getParent();
95c75e76d11b LLVM 3.4
Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp>
parents:
diff changeset
241
95c75e76d11b LLVM 3.4
Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp>
parents:
diff changeset
242 // Determine the block in which the use happens. PHI nodes use
95c75e76d11b LLVM 3.4
Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp>
parents:
diff changeset
243 // their operands on edges; simulate this by thinking of the use
95c75e76d11b LLVM 3.4
Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp>
parents:
diff changeset
244 // happening at the end of the predecessor block.
95c75e76d11b LLVM 3.4
Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp>
parents:
diff changeset
245 const BasicBlock *UseBB;
95c75e76d11b LLVM 3.4
Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp>
parents:
diff changeset
246 if (PHINode *PN = dyn_cast<PHINode>(UserInst))
95c75e76d11b LLVM 3.4
Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp>
parents:
diff changeset
247 UseBB = PN->getIncomingBlock(U);
95c75e76d11b LLVM 3.4
Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp>
parents:
diff changeset
248 else
95c75e76d11b LLVM 3.4
Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp>
parents:
diff changeset
249 UseBB = UserInst->getParent();
95c75e76d11b LLVM 3.4
Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp>
parents:
diff changeset
250
95c75e76d11b LLVM 3.4
Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp>
parents:
diff changeset
251 // Any unreachable use is dominated, even if Def == User.
95c75e76d11b LLVM 3.4
Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp>
parents:
diff changeset
252 if (!isReachableFromEntry(UseBB))
95c75e76d11b LLVM 3.4
Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp>
parents:
diff changeset
253 return true;
95c75e76d11b LLVM 3.4
Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp>
parents:
diff changeset
254
95c75e76d11b LLVM 3.4
Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp>
parents:
diff changeset
255 // Unreachable definitions don't dominate anything.
95c75e76d11b LLVM 3.4
Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp>
parents:
diff changeset
256 if (!isReachableFromEntry(DefBB))
95c75e76d11b LLVM 3.4
Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp>
parents:
diff changeset
257 return false;
95c75e76d11b LLVM 3.4
Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp>
parents:
diff changeset
258
95c75e76d11b LLVM 3.4
Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp>
parents:
diff changeset
259 // Invoke instructions define their return values on the edges
95c75e76d11b LLVM 3.4
Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp>
parents:
diff changeset
260 // to their normal successors, so we have to handle them specially.
95c75e76d11b LLVM 3.4
Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp>
parents:
diff changeset
261 // Among other things, this means they don't dominate anything in
95c75e76d11b LLVM 3.4
Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp>
parents:
diff changeset
262 // their own block, except possibly a phi, so we don't need to
95c75e76d11b LLVM 3.4
Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp>
parents:
diff changeset
263 // walk the block in any case.
95c75e76d11b LLVM 3.4
Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp>
parents:
diff changeset
264 if (const InvokeInst *II = dyn_cast<InvokeInst>(Def)) {
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265 BasicBlock *NormalDest = II->getNormalDest();
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266 BasicBlockEdge E(DefBB, NormalDest);
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267 return dominates(E, U);
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268 }
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269
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270 // If the def and use are in different blocks, do a simple CFG dominator
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271 // tree query.
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272 if (DefBB != UseBB)
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273 return dominates(DefBB, UseBB);
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274
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275 // Ok, def and use are in the same block. If the def is an invoke, it
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276 // doesn't dominate anything in the block. If it's a PHI, it dominates
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277 // everything in the block.
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278 if (isa<PHINode>(UserInst))
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279 return true;
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280
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281 // Otherwise, just loop through the basic block until we find Def or User.
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282 BasicBlock::const_iterator I = DefBB->begin();
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283 for (; &*I != Def && &*I != UserInst; ++I)
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284 /*empty*/;
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285
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286 return &*I != UserInst;
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287 }
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288
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289 bool DominatorTree::isReachableFromEntry(const Use &U) const {
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290 Instruction *I = dyn_cast<Instruction>(U.getUser());
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291
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292 // ConstantExprs aren't really reachable from the entry block, but they
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293 // don't need to be treated like unreachable code either.
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294 if (!I) return true;
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295
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296 // PHI nodes use their operands on their incoming edges.
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297 if (PHINode *PN = dyn_cast<PHINode>(I))
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298 return isReachableFromEntry(PN->getIncomingBlock(U));
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299
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300 // Everything else uses their operands in their own block.
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301 return isReachableFromEntry(I->getParent());
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302 }