MemoryDependenceAnalysis.h revision dd696052f0e4ecc973d105be19cf1b4b72f9a0c4
1//===- llvm/Analysis/MemoryDependenceAnalysis.h - Memory Deps --*- 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 the MemoryDependenceAnalysis analysis pass. 11// 12//===----------------------------------------------------------------------===// 13 14#ifndef LLVM_ANALYSIS_MEMORY_DEPENDENCE_H 15#define LLVM_ANALYSIS_MEMORY_DEPENDENCE_H 16 17#include "llvm/BasicBlock.h" 18#include "llvm/Pass.h" 19#include "llvm/ADT/DenseMap.h" 20#include "llvm/ADT/SmallPtrSet.h" 21#include "llvm/ADT/OwningPtr.h" 22#include "llvm/ADT/PointerIntPair.h" 23 24namespace llvm { 25 class Function; 26 class FunctionPass; 27 class Instruction; 28 class CallSite; 29 class AliasAnalysis; 30 class TargetData; 31 class MemoryDependenceAnalysis; 32 class PredIteratorCache; 33 class DominatorTree; 34 35 /// MemDepResult - A memory dependence query can return one of three different 36 /// answers, described below. 37 class MemDepResult { 38 enum DepType { 39 /// Invalid - Clients of MemDep never see this. 40 Invalid = 0, 41 42 /// Clobber - This is a dependence on the specified instruction which 43 /// clobbers the desired value. The pointer member of the MemDepResult 44 /// pair holds the instruction that clobbers the memory. For example, 45 /// this occurs when we see a may-aliased store to the memory location we 46 /// care about. 47 Clobber, 48 49 /// Def - This is a dependence on the specified instruction which 50 /// defines/produces the desired memory location. The pointer member of 51 /// the MemDepResult pair holds the instruction that defines the memory. 52 /// Cases of interest: 53 /// 1. This could be a load or store for dependence queries on 54 /// load/store. The value loaded or stored is the produced value. 55 /// Note that the pointer operand may be different than that of the 56 /// queried pointer due to must aliases and phi translation. Note 57 /// that the def may not be the same type as the query, the pointers 58 /// may just be must aliases. 59 /// 2. For loads and stores, this could be an allocation instruction. In 60 /// this case, the load is loading an undef value or a store is the 61 /// first store to (that part of) the allocation. 62 /// 3. Dependence queries on calls return Def only when they are 63 /// readonly calls with identical callees and no intervening 64 /// clobbers. No validation is done that the operands to the calls 65 /// are the same. 66 Def, 67 68 /// NonLocal - This marker indicates that the query has no dependency in 69 /// the specified block. To find out more, the client should query other 70 /// predecessor blocks. 71 NonLocal 72 }; 73 typedef PointerIntPair<Instruction*, 2, DepType> PairTy; 74 PairTy Value; 75 explicit MemDepResult(PairTy V) : Value(V) {} 76 public: 77 MemDepResult() : Value(0, Invalid) {} 78 79 /// get methods: These are static ctor methods for creating various 80 /// MemDepResult kinds. 81 static MemDepResult getDef(Instruction *Inst) { 82 return MemDepResult(PairTy(Inst, Def)); 83 } 84 static MemDepResult getClobber(Instruction *Inst) { 85 return MemDepResult(PairTy(Inst, Clobber)); 86 } 87 static MemDepResult getNonLocal() { 88 return MemDepResult(PairTy(0, NonLocal)); 89 } 90 91 /// isClobber - Return true if this MemDepResult represents a query that is 92 /// a instruction clobber dependency. 93 bool isClobber() const { return Value.getInt() == Clobber; } 94 95 /// isDef - Return true if this MemDepResult represents a query that is 96 /// a instruction definition dependency. 97 bool isDef() const { return Value.getInt() == Def; } 98 99 /// isNonLocal - Return true if this MemDepResult represents a query that 100 /// is transparent to the start of the block, but where a non-local hasn't 101 /// been done. 102 bool isNonLocal() const { return Value.getInt() == NonLocal; } 103 104 /// getInst() - If this is a normal dependency, return the instruction that 105 /// is depended on. Otherwise, return null. 106 Instruction *getInst() const { return Value.getPointer(); } 107 108 bool operator==(const MemDepResult &M) const { return Value == M.Value; } 109 bool operator!=(const MemDepResult &M) const { return Value != M.Value; } 110 bool operator<(const MemDepResult &M) const { return Value < M.Value; } 111 bool operator>(const MemDepResult &M) const { return Value > M.Value; } 112 private: 113 friend class MemoryDependenceAnalysis; 114 /// Dirty - Entries with this marker occur in a LocalDeps map or 115 /// NonLocalDeps map when the instruction they previously referenced was 116 /// removed from MemDep. In either case, the entry may include an 117 /// instruction pointer. If so, the pointer is an instruction in the 118 /// block where scanning can start from, saving some work. 119 /// 120 /// In a default-constructed MemDepResult object, the type will be Dirty 121 /// and the instruction pointer will be null. 122 /// 123 124 /// isDirty - Return true if this is a MemDepResult in its dirty/invalid. 125 /// state. 126 bool isDirty() const { return Value.getInt() == Invalid; } 127 128 static MemDepResult getDirty(Instruction *Inst) { 129 return MemDepResult(PairTy(Inst, Invalid)); 130 } 131 }; 132 133 /// MemoryDependenceAnalysis - This is an analysis that determines, for a 134 /// given memory operation, what preceding memory operations it depends on. 135 /// It builds on alias analysis information, and tries to provide a lazy, 136 /// caching interface to a common kind of alias information query. 137 /// 138 /// The dependency information returned is somewhat unusual, but is pragmatic. 139 /// If queried about a store or call that might modify memory, the analysis 140 /// will return the instruction[s] that may either load from that memory or 141 /// store to it. If queried with a load or call that can never modify memory, 142 /// the analysis will return calls and stores that might modify the pointer, 143 /// but generally does not return loads unless a) they are volatile, or 144 /// b) they load from *must-aliased* pointers. Returning a dependence on 145 /// must-alias'd pointers instead of all pointers interacts well with the 146 /// internal caching mechanism. 147 /// 148 class MemoryDependenceAnalysis : public FunctionPass { 149 // A map from instructions to their dependency. 150 typedef DenseMap<Instruction*, MemDepResult> LocalDepMapType; 151 LocalDepMapType LocalDeps; 152 153 public: 154 typedef std::pair<BasicBlock*, MemDepResult> NonLocalDepEntry; 155 typedef std::vector<NonLocalDepEntry> NonLocalDepInfo; 156 private: 157 /// ValueIsLoadPair - This is a pair<Value*, bool> where the bool is true if 158 /// the dependence is a read only dependence, false if read/write. 159 typedef PointerIntPair<Value*, 1, bool> ValueIsLoadPair; 160 161 /// BBSkipFirstBlockPair - This pair is used when caching information for a 162 /// block. If the pointer is null, the cache value is not a full query that 163 /// starts at the specified block. If non-null, the bool indicates whether 164 /// or not the contents of the block was skipped. 165 typedef PointerIntPair<BasicBlock*, 1, bool> BBSkipFirstBlockPair; 166 167 /// CachedNonLocalPointerInfo - This map stores the cached results of doing 168 /// a pointer lookup at the bottom of a block. The key of this map is the 169 /// pointer+isload bit, the value is a list of <bb->result> mappings. 170 typedef DenseMap<ValueIsLoadPair, std::pair<BBSkipFirstBlockPair, 171 NonLocalDepInfo> > CachedNonLocalPointerInfo; 172 CachedNonLocalPointerInfo NonLocalPointerDeps; 173 174 // A map from instructions to their non-local pointer dependencies. 175 typedef DenseMap<Instruction*, 176 SmallPtrSet<ValueIsLoadPair, 4> > ReverseNonLocalPtrDepTy; 177 ReverseNonLocalPtrDepTy ReverseNonLocalPtrDeps; 178 179 180 /// PerInstNLInfo - This is the instruction we keep for each cached access 181 /// that we have for an instruction. The pointer is an owning pointer and 182 /// the bool indicates whether we have any dirty bits in the set. 183 typedef std::pair<NonLocalDepInfo, bool> PerInstNLInfo; 184 185 // A map from instructions to their non-local dependencies. 186 typedef DenseMap<Instruction*, PerInstNLInfo> NonLocalDepMapType; 187 188 NonLocalDepMapType NonLocalDeps; 189 190 // A reverse mapping from dependencies to the dependees. This is 191 // used when removing instructions to keep the cache coherent. 192 typedef DenseMap<Instruction*, 193 SmallPtrSet<Instruction*, 4> > ReverseDepMapType; 194 ReverseDepMapType ReverseLocalDeps; 195 196 // A reverse mapping form dependencies to the non-local dependees. 197 ReverseDepMapType ReverseNonLocalDeps; 198 199 /// Current AA implementation, just a cache. 200 AliasAnalysis *AA; 201 TargetData *TD; 202 OwningPtr<PredIteratorCache> PredCache; 203 public: 204 MemoryDependenceAnalysis(); 205 ~MemoryDependenceAnalysis(); 206 static char ID; 207 208 /// Pass Implementation stuff. This doesn't do any analysis eagerly. 209 bool runOnFunction(Function &); 210 211 /// Clean up memory in between runs 212 void releaseMemory(); 213 214 /// getAnalysisUsage - Does not modify anything. It uses Value Numbering 215 /// and Alias Analysis. 216 /// 217 virtual void getAnalysisUsage(AnalysisUsage &AU) const; 218 219 /// getDependency - Return the instruction on which a memory operation 220 /// depends. See the class comment for more details. It is illegal to call 221 /// this on non-memory instructions. 222 MemDepResult getDependency(Instruction *QueryInst); 223 224 /// getNonLocalCallDependency - Perform a full dependency query for the 225 /// specified call, returning the set of blocks that the value is 226 /// potentially live across. The returned set of results will include a 227 /// "NonLocal" result for all blocks where the value is live across. 228 /// 229 /// This method assumes the instruction returns a "NonLocal" dependency 230 /// within its own block. 231 /// 232 /// This returns a reference to an internal data structure that may be 233 /// invalidated on the next non-local query or when an instruction is 234 /// removed. Clients must copy this data if they want it around longer than 235 /// that. 236 const NonLocalDepInfo &getNonLocalCallDependency(CallSite QueryCS); 237 238 239 /// getNonLocalPointerDependency - Perform a full dependency query for an 240 /// access to the specified (non-volatile) memory location, returning the 241 /// set of instructions that either define or clobber the value. 242 /// 243 /// This method assumes the pointer has a "NonLocal" dependency within BB. 244 void getNonLocalPointerDependency(Value *Pointer, bool isLoad, 245 BasicBlock *BB, 246 SmallVectorImpl<NonLocalDepEntry> &Result); 247 248 /// GetPHITranslatedValue - Find an available version of the specified value 249 /// PHI translated across the specified edge. If MemDep isn't able to 250 /// satisfy this request, it returns null. 251 Value *GetPHITranslatedValue(Value *V, 252 BasicBlock *CurBB, BasicBlock *PredBB, 253 const TargetData *TD) const; 254 255 /// GetAvailablePHITranslatedValue - Return the value computed by 256 /// PHITranslatePointer if it dominates PredBB, otherwise return null. 257 Value *GetAvailablePHITranslatedValue(Value *V, 258 BasicBlock *CurBB, BasicBlock *PredBB, 259 const TargetData *TD, 260 const DominatorTree &DT) const; 261 262 /// InsertPHITranslatedPointer - Insert a computation of the PHI translated 263 /// version of 'V' for the edge PredBB->CurBB into the end of the PredBB 264 /// block. All newly created instructions are added to the NewInsts list. 265 Value *InsertPHITranslatedPointer(Value *V, 266 BasicBlock *CurBB, BasicBlock *PredBB, 267 const TargetData *TD, 268 const DominatorTree &DT, 269 SmallVectorImpl<Instruction*> &NewInsts) const; 270 271 /// removeInstruction - Remove an instruction from the dependence analysis, 272 /// updating the dependence of instructions that previously depended on it. 273 void removeInstruction(Instruction *InstToRemove); 274 275 /// invalidateCachedPointerInfo - This method is used to invalidate cached 276 /// information about the specified pointer, because it may be too 277 /// conservative in memdep. This is an optional call that can be used when 278 /// the client detects an equivalence between the pointer and some other 279 /// value and replaces the other value with ptr. This can make Ptr available 280 /// in more places that cached info does not necessarily keep. 281 void invalidateCachedPointerInfo(Value *Ptr); 282 283 private: 284 MemDepResult getPointerDependencyFrom(Value *Pointer, uint64_t MemSize, 285 bool isLoad, 286 BasicBlock::iterator ScanIt, 287 BasicBlock *BB); 288 MemDepResult getCallSiteDependencyFrom(CallSite C, bool isReadOnlyCall, 289 BasicBlock::iterator ScanIt, 290 BasicBlock *BB); 291 bool getNonLocalPointerDepFromBB(Value *Pointer, uint64_t Size, 292 bool isLoad, BasicBlock *BB, 293 SmallVectorImpl<NonLocalDepEntry> &Result, 294 DenseMap<BasicBlock*, Value*> &Visited, 295 bool SkipFirstBlock = false); 296 MemDepResult GetNonLocalInfoForBlock(Value *Pointer, uint64_t PointeeSize, 297 bool isLoad, BasicBlock *BB, 298 NonLocalDepInfo *Cache, 299 unsigned NumSortedEntries); 300 301 void RemoveCachedNonLocalPointerDependencies(ValueIsLoadPair P); 302 303 /// verifyRemoved - Verify that the specified instruction does not occur 304 /// in our internal data structures. 305 void verifyRemoved(Instruction *Inst) const; 306 307 }; 308 309} // End llvm namespace 310 311#endif 312