MemoryDependenceAnalysis.h revision 484d4a30c055eef3101d01a7a468db3413dd20d3
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/Support/ValueHandle.h" 20#include "llvm/ADT/DenseMap.h" 21#include "llvm/ADT/SmallPtrSet.h" 22#include "llvm/ADT/OwningPtr.h" 23#include "llvm/ADT/PointerIntPair.h" 24 25namespace llvm { 26 class Function; 27 class FunctionPass; 28 class Instruction; 29 class CallSite; 30 class AliasAnalysis; 31 class TargetData; 32 class MemoryDependenceAnalysis; 33 class PredIteratorCache; 34 class DominatorTree; 35 class PHITransAddr; 36 37 /// MemDepResult - A memory dependence query can return one of three different 38 /// answers, described below. 39 class MemDepResult { 40 enum DepType { 41 /// Invalid - Clients of MemDep never see this. 42 Invalid = 0, 43 44 /// Clobber - This is a dependence on the specified instruction which 45 /// clobbers the desired value. The pointer member of the MemDepResult 46 /// pair holds the instruction that clobbers the memory. For example, 47 /// this occurs when we see a may-aliased store to the memory location we 48 /// care about. 49 Clobber, 50 51 /// Def - This is a dependence on the specified instruction which 52 /// defines/produces the desired memory location. The pointer member of 53 /// the MemDepResult pair holds the instruction that defines the memory. 54 /// Cases of interest: 55 /// 1. This could be a load or store for dependence queries on 56 /// load/store. The value loaded or stored is the produced value. 57 /// Note that the pointer operand may be different than that of the 58 /// queried pointer due to must aliases and phi translation. Note 59 /// that the def may not be the same type as the query, the pointers 60 /// may just be must aliases. 61 /// 2. For loads and stores, this could be an allocation instruction. In 62 /// this case, the load is loading an undef value or a store is the 63 /// first store to (that part of) the allocation. 64 /// 3. Dependence queries on calls return Def only when they are 65 /// readonly calls or memory use intrinsics with identical callees 66 /// and no intervening clobbers. No validation is done that the 67 /// operands to the calls are the same. 68 Def, 69 70 /// NonLocal - This marker indicates that the query has no dependency in 71 /// the specified block. To find out more, the client should query other 72 /// predecessor blocks. 73 NonLocal 74 }; 75 typedef PointerIntPair<Instruction*, 2, DepType> PairTy; 76 PairTy Value; 77 explicit MemDepResult(PairTy V) : Value(V) {} 78 public: 79 MemDepResult() : Value(0, Invalid) {} 80 81 /// get methods: These are static ctor methods for creating various 82 /// MemDepResult kinds. 83 static MemDepResult getDef(Instruction *Inst) { 84 return MemDepResult(PairTy(Inst, Def)); 85 } 86 static MemDepResult getClobber(Instruction *Inst) { 87 return MemDepResult(PairTy(Inst, Clobber)); 88 } 89 static MemDepResult getNonLocal() { 90 return MemDepResult(PairTy(0, NonLocal)); 91 } 92 93 /// isClobber - Return true if this MemDepResult represents a query that is 94 /// a instruction clobber dependency. 95 bool isClobber() const { return Value.getInt() == Clobber; } 96 97 /// isDef - Return true if this MemDepResult represents a query that is 98 /// a instruction definition dependency. 99 bool isDef() const { return Value.getInt() == Def; } 100 101 /// isNonLocal - Return true if this MemDepResult represents a query that 102 /// is transparent to the start of the block, but where a non-local hasn't 103 /// been done. 104 bool isNonLocal() const { return Value.getInt() == NonLocal; } 105 106 /// getInst() - If this is a normal dependency, return the instruction that 107 /// is depended on. Otherwise, return null. 108 Instruction *getInst() const { return Value.getPointer(); } 109 110 bool operator==(const MemDepResult &M) const { return Value == M.Value; } 111 bool operator!=(const MemDepResult &M) const { return Value != M.Value; } 112 bool operator<(const MemDepResult &M) const { return Value < M.Value; } 113 bool operator>(const MemDepResult &M) const { return Value > M.Value; } 114 private: 115 friend class MemoryDependenceAnalysis; 116 /// Dirty - Entries with this marker occur in a LocalDeps map or 117 /// NonLocalDeps map when the instruction they previously referenced was 118 /// removed from MemDep. In either case, the entry may include an 119 /// instruction pointer. If so, the pointer is an instruction in the 120 /// block where scanning can start from, saving some work. 121 /// 122 /// In a default-constructed MemDepResult object, the type will be Dirty 123 /// and the instruction pointer will be null. 124 /// 125 126 /// isDirty - Return true if this is a MemDepResult in its dirty/invalid. 127 /// state. 128 bool isDirty() const { return Value.getInt() == Invalid; } 129 130 static MemDepResult getDirty(Instruction *Inst) { 131 return MemDepResult(PairTy(Inst, Invalid)); 132 } 133 }; 134 135 /// NonLocalDepResult - This is a result from a NonLocal dependence query. 136 /// For each BasicBlock (the BB entry) it keeps a MemDepResult and the 137 /// (potentially phi translated) address that was live in the block. 138 class NonLocalDepResult { 139 BasicBlock *BB; 140 MemDepResult Result; 141 Value *Address; 142 public: 143 NonLocalDepResult(BasicBlock *bb, MemDepResult result, Value *address) 144 : BB(bb), Result(result), Address(address) {} 145 146 // BB is the sort key, it can't be changed. 147 BasicBlock *getBB() const { return BB; } 148 149 void setResult(const MemDepResult &R, Value *Addr) { 150 Result = R; 151 Address = Addr; 152 } 153 154 const MemDepResult &getResult() const { return Result; } 155 156 /// getAddress - Return the address of this pointer in this block. This can 157 /// be different than the address queried for the non-local result because 158 /// of phi translation. This returns null if the address was not available 159 /// in a block (i.e. because phi translation failed) or if this is a cached 160 /// result and that address was deleted. 161 /// 162 /// The address is always null for a non-local 'call' dependence. 163 Value *getAddress() const { return Address; } 164 }; 165 166 /// NonLocalDepEntry - This is an entry in the NonLocalDepInfo cache. For 167 /// each BasicBlock (the BB entry) it keeps a MemDepResult. 168 class NonLocalDepEntry { 169 BasicBlock *BB; 170 MemDepResult Result; 171 public: 172 NonLocalDepEntry(BasicBlock *bb, MemDepResult result) 173 : BB(bb), Result(result) {} 174 175 // This is used for searches. 176 NonLocalDepEntry(BasicBlock *bb) : BB(bb) {} 177 178 // BB is the sort key, it can't be changed. 179 BasicBlock *getBB() const { return BB; } 180 181 void setResult(const MemDepResult &R) { Result = R; } 182 183 const MemDepResult &getResult() const { return Result; } 184 185 bool operator<(const NonLocalDepEntry &RHS) const { 186 return BB < RHS.BB; 187 } 188 }; 189 190 /// MemoryDependenceAnalysis - This is an analysis that determines, for a 191 /// given memory operation, what preceding memory operations it depends on. 192 /// It builds on alias analysis information, and tries to provide a lazy, 193 /// caching interface to a common kind of alias information query. 194 /// 195 /// The dependency information returned is somewhat unusual, but is pragmatic. 196 /// If queried about a store or call that might modify memory, the analysis 197 /// will return the instruction[s] that may either load from that memory or 198 /// store to it. If queried with a load or call that can never modify memory, 199 /// the analysis will return calls and stores that might modify the pointer, 200 /// but generally does not return loads unless a) they are volatile, or 201 /// b) they load from *must-aliased* pointers. Returning a dependence on 202 /// must-alias'd pointers instead of all pointers interacts well with the 203 /// internal caching mechanism. 204 /// 205 class MemoryDependenceAnalysis : public FunctionPass { 206 // A map from instructions to their dependency. 207 typedef DenseMap<Instruction*, MemDepResult> LocalDepMapType; 208 LocalDepMapType LocalDeps; 209 210 public: 211 typedef std::vector<NonLocalDepEntry> NonLocalDepInfo; 212 private: 213 /// ValueIsLoadPair - This is a pair<Value*, bool> where the bool is true if 214 /// the dependence is a read only dependence, false if read/write. 215 typedef PointerIntPair<Value*, 1, bool> ValueIsLoadPair; 216 217 /// BBSkipFirstBlockPair - This pair is used when caching information for a 218 /// block. If the pointer is null, the cache value is not a full query that 219 /// starts at the specified block. If non-null, the bool indicates whether 220 /// or not the contents of the block was skipped. 221 typedef PointerIntPair<BasicBlock*, 1, bool> BBSkipFirstBlockPair; 222 223 /// CachedNonLocalPointerInfo - This map stores the cached results of doing 224 /// a pointer lookup at the bottom of a block. The key of this map is the 225 /// pointer+isload bit, the value is a list of <bb->result> mappings. 226 typedef DenseMap<ValueIsLoadPair, std::pair<BBSkipFirstBlockPair, 227 NonLocalDepInfo> > CachedNonLocalPointerInfo; 228 CachedNonLocalPointerInfo NonLocalPointerDeps; 229 230 // A map from instructions to their non-local pointer dependencies. 231 typedef DenseMap<Instruction*, 232 SmallPtrSet<ValueIsLoadPair, 4> > ReverseNonLocalPtrDepTy; 233 ReverseNonLocalPtrDepTy ReverseNonLocalPtrDeps; 234 235 236 /// PerInstNLInfo - This is the instruction we keep for each cached access 237 /// that we have for an instruction. The pointer is an owning pointer and 238 /// the bool indicates whether we have any dirty bits in the set. 239 typedef std::pair<NonLocalDepInfo, bool> PerInstNLInfo; 240 241 // A map from instructions to their non-local dependencies. 242 typedef DenseMap<Instruction*, PerInstNLInfo> NonLocalDepMapType; 243 244 NonLocalDepMapType NonLocalDeps; 245 246 // A reverse mapping from dependencies to the dependees. This is 247 // used when removing instructions to keep the cache coherent. 248 typedef DenseMap<Instruction*, 249 SmallPtrSet<Instruction*, 4> > ReverseDepMapType; 250 ReverseDepMapType ReverseLocalDeps; 251 252 // A reverse mapping from dependencies to the non-local dependees. 253 ReverseDepMapType ReverseNonLocalDeps; 254 255 /// Current AA implementation, just a cache. 256 AliasAnalysis *AA; 257 TargetData *TD; 258 OwningPtr<PredIteratorCache> PredCache; 259 public: 260 MemoryDependenceAnalysis(); 261 ~MemoryDependenceAnalysis(); 262 static char ID; 263 264 /// Pass Implementation stuff. This doesn't do any analysis eagerly. 265 bool runOnFunction(Function &); 266 267 /// Clean up memory in between runs 268 void releaseMemory(); 269 270 /// getAnalysisUsage - Does not modify anything. It uses Value Numbering 271 /// and Alias Analysis. 272 /// 273 virtual void getAnalysisUsage(AnalysisUsage &AU) const; 274 275 /// getDependency - Return the instruction on which a memory operation 276 /// depends. See the class comment for more details. It is illegal to call 277 /// this on non-memory instructions. 278 MemDepResult getDependency(Instruction *QueryInst); 279 280 /// getNonLocalCallDependency - Perform a full dependency query for the 281 /// specified call, returning the set of blocks that the value is 282 /// potentially live across. The returned set of results will include a 283 /// "NonLocal" result for all blocks where the value is live across. 284 /// 285 /// This method assumes the instruction returns a "NonLocal" dependency 286 /// within its own block. 287 /// 288 /// This returns a reference to an internal data structure that may be 289 /// invalidated on the next non-local query or when an instruction is 290 /// removed. Clients must copy this data if they want it around longer than 291 /// that. 292 const NonLocalDepInfo &getNonLocalCallDependency(CallSite QueryCS); 293 294 295 /// getNonLocalPointerDependency - Perform a full dependency query for an 296 /// access to the specified (non-volatile) memory location, returning the 297 /// set of instructions that either define or clobber the value. 298 /// 299 /// This method assumes the pointer has a "NonLocal" dependency within BB. 300 void getNonLocalPointerDependency(Value *Pointer, bool isLoad, 301 BasicBlock *BB, 302 SmallVectorImpl<NonLocalDepResult> &Result); 303 304 /// removeInstruction - Remove an instruction from the dependence analysis, 305 /// updating the dependence of instructions that previously depended on it. 306 void removeInstruction(Instruction *InstToRemove); 307 308 /// invalidateCachedPointerInfo - This method is used to invalidate cached 309 /// information about the specified pointer, because it may be too 310 /// conservative in memdep. This is an optional call that can be used when 311 /// the client detects an equivalence between the pointer and some other 312 /// value and replaces the other value with ptr. This can make Ptr available 313 /// in more places that cached info does not necessarily keep. 314 void invalidateCachedPointerInfo(Value *Ptr); 315 316 /// invalidateCachedPredecessors - Clear the PredIteratorCache info. 317 /// This needs to be done when the CFG changes, e.g., due to splitting 318 /// critical edges. 319 void invalidateCachedPredecessors(); 320 321 private: 322 MemDepResult getPointerDependencyFrom(Value *Pointer, uint64_t MemSize, 323 bool isLoad, 324 BasicBlock::iterator ScanIt, 325 BasicBlock *BB); 326 MemDepResult getCallSiteDependencyFrom(CallSite C, bool isReadOnlyCall, 327 BasicBlock::iterator ScanIt, 328 BasicBlock *BB); 329 bool getNonLocalPointerDepFromBB(const PHITransAddr &Pointer, uint64_t Size, 330 bool isLoad, BasicBlock *BB, 331 SmallVectorImpl<NonLocalDepResult> &Result, 332 DenseMap<BasicBlock*, Value*> &Visited, 333 bool SkipFirstBlock = false); 334 MemDepResult GetNonLocalInfoForBlock(Value *Pointer, uint64_t PointeeSize, 335 bool isLoad, BasicBlock *BB, 336 NonLocalDepInfo *Cache, 337 unsigned NumSortedEntries); 338 339 void RemoveCachedNonLocalPointerDependencies(ValueIsLoadPair P); 340 341 /// verifyRemoved - Verify that the specified instruction does not occur 342 /// in our internal data structures. 343 void verifyRemoved(Instruction *Inst) const; 344 345 }; 346 347} // End llvm namespace 348 349#endif 350