1//==- llvm/CodeGen/MachineDominators.h - Machine Dom Calculation -*- C++ -*-==// 2// 3// The LLVM Compiler Infrastructure 4// 5// This file is distributed under the University of Illinois Open Source 6// License. See LICENSE.TXT for details. 7// 8//===----------------------------------------------------------------------===// 9// 10// This file defines classes mirroring those in llvm/Analysis/Dominators.h, 11// but for target-specific code rather than target-independent IR. 12// 13//===----------------------------------------------------------------------===// 14 15#ifndef LLVM_CODEGEN_MACHINEDOMINATORS_H 16#define LLVM_CODEGEN_MACHINEDOMINATORS_H 17 18#include "llvm/ADT/SmallSet.h" 19#include "llvm/ADT/SmallVector.h" 20#include "llvm/CodeGen/MachineBasicBlock.h" 21#include "llvm/CodeGen/MachineFunctionPass.h" 22#include "llvm/CodeGen/MachineInstr.h" 23#include "llvm/Support/GenericDomTree.h" 24#include "llvm/Support/GenericDomTreeConstruction.h" 25#include <cassert> 26#include <memory> 27#include <vector> 28 29namespace llvm { 30 31template <> 32inline void DominatorTreeBase<MachineBasicBlock, false>::addRoot( 33 MachineBasicBlock *MBB) { 34 this->Roots.push_back(MBB); 35} 36 37extern template class DomTreeNodeBase<MachineBasicBlock>; 38extern template class DominatorTreeBase<MachineBasicBlock, false>; // DomTree 39extern template class DominatorTreeBase<MachineBasicBlock, true>; // PostDomTree 40 41using MachineDomTreeNode = DomTreeNodeBase<MachineBasicBlock>; 42 43//===------------------------------------- 44/// DominatorTree Class - Concrete subclass of DominatorTreeBase that is used to 45/// compute a normal dominator tree. 46/// 47class MachineDominatorTree : public MachineFunctionPass { 48 /// \brief Helper structure used to hold all the basic blocks 49 /// involved in the split of a critical edge. 50 struct CriticalEdge { 51 MachineBasicBlock *FromBB; 52 MachineBasicBlock *ToBB; 53 MachineBasicBlock *NewBB; 54 }; 55 56 /// \brief Pile up all the critical edges to be split. 57 /// The splitting of a critical edge is local and thus, it is possible 58 /// to apply several of those changes at the same time. 59 mutable SmallVector<CriticalEdge, 32> CriticalEdgesToSplit; 60 61 /// \brief Remember all the basic blocks that are inserted during 62 /// edge splitting. 63 /// Invariant: NewBBs == all the basic blocks contained in the NewBB 64 /// field of all the elements of CriticalEdgesToSplit. 65 /// I.e., forall elt in CriticalEdgesToSplit, it exists BB in NewBBs 66 /// such as BB == elt.NewBB. 67 mutable SmallSet<MachineBasicBlock *, 32> NewBBs; 68 69 /// The DominatorTreeBase that is used to compute a normal dominator tree 70 std::unique_ptr<DomTreeBase<MachineBasicBlock>> DT; 71 72 /// \brief Apply all the recorded critical edges to the DT. 73 /// This updates the underlying DT information in a way that uses 74 /// the fast query path of DT as much as possible. 75 /// 76 /// \post CriticalEdgesToSplit.empty(). 77 void applySplitCriticalEdges() const; 78 79public: 80 static char ID; // Pass ID, replacement for typeid 81 82 MachineDominatorTree(); 83 84 DomTreeBase<MachineBasicBlock> &getBase() { 85 if (!DT) DT.reset(new DomTreeBase<MachineBasicBlock>()); 86 applySplitCriticalEdges(); 87 return *DT; 88 } 89 90 void getAnalysisUsage(AnalysisUsage &AU) const override; 91 92 /// getRoots - Return the root blocks of the current CFG. This may include 93 /// multiple blocks if we are computing post dominators. For forward 94 /// dominators, this will always be a single block (the entry node). 95 /// 96 inline const SmallVectorImpl<MachineBasicBlock*> &getRoots() const { 97 applySplitCriticalEdges(); 98 return DT->getRoots(); 99 } 100 101 inline MachineBasicBlock *getRoot() const { 102 applySplitCriticalEdges(); 103 return DT->getRoot(); 104 } 105 106 inline MachineDomTreeNode *getRootNode() const { 107 applySplitCriticalEdges(); 108 return DT->getRootNode(); 109 } 110 111 bool runOnMachineFunction(MachineFunction &F) override; 112 113 inline bool dominates(const MachineDomTreeNode* A, 114 const MachineDomTreeNode* B) const { 115 applySplitCriticalEdges(); 116 return DT->dominates(A, B); 117 } 118 119 inline bool dominates(const MachineBasicBlock* A, 120 const MachineBasicBlock* B) const { 121 applySplitCriticalEdges(); 122 return DT->dominates(A, B); 123 } 124 125 // dominates - Return true if A dominates B. This performs the 126 // special checks necessary if A and B are in the same basic block. 127 bool dominates(const MachineInstr *A, const MachineInstr *B) const { 128 applySplitCriticalEdges(); 129 const MachineBasicBlock *BBA = A->getParent(), *BBB = B->getParent(); 130 if (BBA != BBB) return DT->dominates(BBA, BBB); 131 132 // Loop through the basic block until we find A or B. 133 MachineBasicBlock::const_iterator I = BBA->begin(); 134 for (; &*I != A && &*I != B; ++I) 135 /*empty*/ ; 136 137 //if(!DT.IsPostDominators) { 138 // A dominates B if it is found first in the basic block. 139 return &*I == A; 140 //} else { 141 // // A post-dominates B if B is found first in the basic block. 142 // return &*I == B; 143 //} 144 } 145 146 inline bool properlyDominates(const MachineDomTreeNode* A, 147 const MachineDomTreeNode* B) const { 148 applySplitCriticalEdges(); 149 return DT->properlyDominates(A, B); 150 } 151 152 inline bool properlyDominates(const MachineBasicBlock* A, 153 const MachineBasicBlock* B) const { 154 applySplitCriticalEdges(); 155 return DT->properlyDominates(A, B); 156 } 157 158 /// findNearestCommonDominator - Find nearest common dominator basic block 159 /// for basic block A and B. If there is no such block then return NULL. 160 inline MachineBasicBlock *findNearestCommonDominator(MachineBasicBlock *A, 161 MachineBasicBlock *B) { 162 applySplitCriticalEdges(); 163 return DT->findNearestCommonDominator(A, B); 164 } 165 166 inline MachineDomTreeNode *operator[](MachineBasicBlock *BB) const { 167 applySplitCriticalEdges(); 168 return DT->getNode(BB); 169 } 170 171 /// getNode - return the (Post)DominatorTree node for the specified basic 172 /// block. This is the same as using operator[] on this class. 173 /// 174 inline MachineDomTreeNode *getNode(MachineBasicBlock *BB) const { 175 applySplitCriticalEdges(); 176 return DT->getNode(BB); 177 } 178 179 /// addNewBlock - Add a new node to the dominator tree information. This 180 /// creates a new node as a child of DomBB dominator node,linking it into 181 /// the children list of the immediate dominator. 182 inline MachineDomTreeNode *addNewBlock(MachineBasicBlock *BB, 183 MachineBasicBlock *DomBB) { 184 applySplitCriticalEdges(); 185 return DT->addNewBlock(BB, DomBB); 186 } 187 188 /// changeImmediateDominator - This method is used to update the dominator 189 /// tree information when a node's immediate dominator changes. 190 /// 191 inline void changeImmediateDominator(MachineBasicBlock *N, 192 MachineBasicBlock* NewIDom) { 193 applySplitCriticalEdges(); 194 DT->changeImmediateDominator(N, NewIDom); 195 } 196 197 inline void changeImmediateDominator(MachineDomTreeNode *N, 198 MachineDomTreeNode* NewIDom) { 199 applySplitCriticalEdges(); 200 DT->changeImmediateDominator(N, NewIDom); 201 } 202 203 /// eraseNode - Removes a node from the dominator tree. Block must not 204 /// dominate any other blocks. Removes node from its immediate dominator's 205 /// children list. Deletes dominator node associated with basic block BB. 206 inline void eraseNode(MachineBasicBlock *BB) { 207 applySplitCriticalEdges(); 208 DT->eraseNode(BB); 209 } 210 211 /// splitBlock - BB is split and now it has one successor. Update dominator 212 /// tree to reflect this change. 213 inline void splitBlock(MachineBasicBlock* NewBB) { 214 applySplitCriticalEdges(); 215 DT->splitBlock(NewBB); 216 } 217 218 /// isReachableFromEntry - Return true if A is dominated by the entry 219 /// block of the function containing it. 220 bool isReachableFromEntry(const MachineBasicBlock *A) { 221 applySplitCriticalEdges(); 222 return DT->isReachableFromEntry(A); 223 } 224 225 void releaseMemory() override; 226 227 void verifyAnalysis() const override; 228 229 void print(raw_ostream &OS, const Module*) const override; 230 231 /// \brief Record that the critical edge (FromBB, ToBB) has been 232 /// split with NewBB. 233 /// This is best to use this method instead of directly update the 234 /// underlying information, because this helps mitigating the 235 /// number of time the DT information is invalidated. 236 /// 237 /// \note Do not use this method with regular edges. 238 /// 239 /// \note To benefit from the compile time improvement incurred by this 240 /// method, the users of this method have to limit the queries to the DT 241 /// interface between two edges splitting. In other words, they have to 242 /// pack the splitting of critical edges as much as possible. 243 void recordSplitCriticalEdge(MachineBasicBlock *FromBB, 244 MachineBasicBlock *ToBB, 245 MachineBasicBlock *NewBB) { 246 bool Inserted = NewBBs.insert(NewBB).second; 247 (void)Inserted; 248 assert(Inserted && 249 "A basic block inserted via edge splitting cannot appear twice"); 250 CriticalEdgesToSplit.push_back({FromBB, ToBB, NewBB}); 251 } 252 253 /// \brief Verify the correctness of the domtree by re-computing it. 254 /// 255 /// This should only be used for debugging as it aborts the program if the 256 /// verification fails. 257 void verifyDomTree() const; 258}; 259 260//===------------------------------------- 261/// DominatorTree GraphTraits specialization so the DominatorTree can be 262/// iterable by generic graph iterators. 263/// 264 265template <class Node, class ChildIterator> 266struct MachineDomTreeGraphTraitsBase { 267 using NodeRef = Node *; 268 using ChildIteratorType = ChildIterator; 269 270 static NodeRef getEntryNode(NodeRef N) { return N; } 271 static ChildIteratorType child_begin(NodeRef N) { return N->begin(); } 272 static ChildIteratorType child_end(NodeRef N) { return N->end(); } 273}; 274 275template <class T> struct GraphTraits; 276 277template <> 278struct GraphTraits<MachineDomTreeNode *> 279 : public MachineDomTreeGraphTraitsBase<MachineDomTreeNode, 280 MachineDomTreeNode::iterator> {}; 281 282template <> 283struct GraphTraits<const MachineDomTreeNode *> 284 : public MachineDomTreeGraphTraitsBase<const MachineDomTreeNode, 285 MachineDomTreeNode::const_iterator> { 286}; 287 288template <> struct GraphTraits<MachineDominatorTree*> 289 : public GraphTraits<MachineDomTreeNode *> { 290 static NodeRef getEntryNode(MachineDominatorTree *DT) { 291 return DT->getRootNode(); 292 } 293}; 294 295} // end namespace llvm 296 297#endif // LLVM_CODEGEN_MACHINEDOMINATORS_H 298