LCOV - code coverage report
Current view: top level - include/llvm/Analysis - MemoryDependenceAnalysis.h (source / functions) Hit Total Coverage
Test: llvm-toolchain.info Lines: 32 35 91.4 %
Date: 2017-09-14 15:23:50 Functions: 5 5 100.0 %
Legend: Lines: hit not hit

          Line data    Source code
       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_MEMORYDEPENDENCEANALYSIS_H
      15             : #define LLVM_ANALYSIS_MEMORYDEPENDENCEANALYSIS_H
      16             : 
      17             : #include "llvm/ADT/DenseMap.h"
      18             : #include "llvm/ADT/Optional.h"
      19             : #include "llvm/ADT/PointerEmbeddedInt.h"
      20             : #include "llvm/ADT/PointerIntPair.h"
      21             : #include "llvm/ADT/PointerSumType.h"
      22             : #include "llvm/ADT/SmallPtrSet.h"
      23             : #include "llvm/Analysis/AliasAnalysis.h"
      24             : #include "llvm/Analysis/MemoryLocation.h"
      25             : #include "llvm/IR/BasicBlock.h"
      26             : #include "llvm/IR/Metadata.h"
      27             : #include "llvm/IR/PassManager.h"
      28             : #include "llvm/IR/PredIteratorCache.h"
      29             : #include "llvm/Pass.h"
      30             : #include "llvm/Support/ErrorHandling.h"
      31             : #include <cassert>
      32             : #include <cstdint>
      33             : #include <utility>
      34             : #include <vector>
      35             : 
      36             : namespace llvm {
      37             : 
      38             : class AssumptionCache;
      39             : class CallSite;
      40             : class DominatorTree;
      41             : class Function;
      42             : class Instruction;
      43             : class LoadInst;
      44             : class PHITransAddr;
      45             : class TargetLibraryInfo;
      46             : class Value;
      47             : 
      48             : /// A memory dependence query can return one of three different answers.
      49             : class MemDepResult {
      50             :   enum DepType {
      51             :     /// Clients of MemDep never see this.
      52             :     ///
      53             :     /// Entries with this marker occur in a LocalDeps map or NonLocalDeps map
      54             :     /// when the instruction they previously referenced was removed from
      55             :     /// MemDep.  In either case, the entry may include an instruction pointer.
      56             :     /// If so, the pointer is an instruction in the block where scanning can
      57             :     /// start from, saving some work.
      58             :     ///
      59             :     /// In a default-constructed MemDepResult object, the type will be Invalid
      60             :     /// and the instruction pointer will be null.
      61             :     Invalid = 0,
      62             : 
      63             :     /// This is a dependence on the specified instruction which clobbers the
      64             :     /// desired value.  The pointer member of the MemDepResult pair holds the
      65             :     /// instruction that clobbers the memory.  For example, this occurs when we
      66             :     /// see a may-aliased store to the memory location we care about.
      67             :     ///
      68             :     /// There are several cases that may be interesting here:
      69             :     ///   1. Loads are clobbered by may-alias stores.
      70             :     ///   2. Loads are considered clobbered by partially-aliased loads.  The
      71             :     ///      client may choose to analyze deeper into these cases.
      72             :     Clobber,
      73             : 
      74             :     /// This is a dependence on the specified instruction which defines or
      75             :     /// produces the desired memory location.  The pointer member of the
      76             :     /// MemDepResult pair holds the instruction that defines the memory.
      77             :     ///
      78             :     /// Cases of interest:
      79             :     ///   1. This could be a load or store for dependence queries on
      80             :     ///      load/store.  The value loaded or stored is the produced value.
      81             :     ///      Note that the pointer operand may be different than that of the
      82             :     ///      queried pointer due to must aliases and phi translation. Note
      83             :     ///      that the def may not be the same type as the query, the pointers
      84             :     ///      may just be must aliases.
      85             :     ///   2. For loads and stores, this could be an allocation instruction. In
      86             :     ///      this case, the load is loading an undef value or a store is the
      87             :     ///      first store to (that part of) the allocation.
      88             :     ///   3. Dependence queries on calls return Def only when they are readonly
      89             :     ///      calls or memory use intrinsics with identical callees and no
      90             :     ///      intervening clobbers.  No validation is done that the operands to
      91             :     ///      the calls are the same.
      92             :     Def,
      93             : 
      94             :     /// This marker indicates that the query has no known dependency in the
      95             :     /// specified block.
      96             :     ///
      97             :     /// More detailed state info is encoded in the upper part of the pair (i.e.
      98             :     /// the Instruction*)
      99             :     Other
     100             :   };
     101             : 
     102             :   /// If DepType is "Other", the upper part of the sum type is an encoding of
     103             :   /// the following more detailed type information.
     104             :   enum OtherType {
     105             :     /// This marker indicates that the query has no dependency in the specified
     106             :     /// block.
     107             :     ///
     108             :     /// To find out more, the client should query other predecessor blocks.
     109             :     NonLocal = 1,
     110             :     /// This marker indicates that the query has no dependency in the specified
     111             :     /// function.
     112             :     NonFuncLocal,
     113             :     /// This marker indicates that the query dependency is unknown.
     114             :     Unknown
     115             :   };
     116             : 
     117             :   using ValueTy = PointerSumType<
     118             :       DepType, PointerSumTypeMember<Invalid, Instruction *>,
     119             :       PointerSumTypeMember<Clobber, Instruction *>,
     120             :       PointerSumTypeMember<Def, Instruction *>,
     121             :       PointerSumTypeMember<Other, PointerEmbeddedInt<OtherType, 3>>>;
     122             :   ValueTy Value;
     123             : 
     124             :   explicit MemDepResult(ValueTy V) : Value(V) {}
     125             : 
     126             : public:
     127     5069446 :   MemDepResult() = default;
     128             : 
     129             :   /// get methods: These are static ctor methods for creating various
     130             :   /// MemDepResult kinds.
     131             :   static MemDepResult getDef(Instruction *Inst) {
     132             :     assert(Inst && "Def requires inst");
     133      384920 :     return MemDepResult(ValueTy::create<Def>(Inst));
     134             :   }
     135             :   static MemDepResult getClobber(Instruction *Inst) {
     136             :     assert(Inst && "Clobber requires inst");
     137      438232 :     return MemDepResult(ValueTy::create<Clobber>(Inst));
     138             :   }
     139             :   static MemDepResult getNonLocal() {
     140     1827806 :     return MemDepResult(ValueTy::create<Other>(NonLocal));
     141             :   }
     142             :   static MemDepResult getNonFuncLocal() {
     143      246146 :     return MemDepResult(ValueTy::create<Other>(NonFuncLocal));
     144             :   }
     145             :   static MemDepResult getUnknown() {
     146     6339998 :     return MemDepResult(ValueTy::create<Other>(Unknown));
     147             :   }
     148             : 
     149             :   /// Tests if this MemDepResult represents a query that is an instruction
     150             :   /// clobber dependency.
     151     5645268 :   bool isClobber() const { return Value.is<Clobber>(); }
     152             : 
     153             :   /// Tests if this MemDepResult represents a query that is an instruction
     154             :   /// definition dependency.
     155    11940788 :   bool isDef() const { return Value.is<Def>(); }
     156             : 
     157             :   /// Tests if this MemDepResult represents a query that is transparent to the
     158             :   /// start of the block, but where a non-local hasn't been done.
     159             :   bool isNonLocal() const {
     160    13093392 :     return Value.is<Other>() && Value.cast<Other>() == NonLocal;
     161             :   }
     162             : 
     163             :   /// Tests if this MemDepResult represents a query that is transparent to the
     164             :   /// start of the function.
     165             :   bool isNonFuncLocal() const {
     166           0 :     return Value.is<Other>() && Value.cast<Other>() == NonFuncLocal;
     167             :   }
     168             : 
     169             :   /// Tests if this MemDepResult represents a query which cannot and/or will
     170             :   /// not be computed.
     171             :   bool isUnknown() const {
     172       25754 :     return Value.is<Other>() && Value.cast<Other>() == Unknown;
     173             :   }
     174             : 
     175             :   /// If this is a normal dependency, returns the instruction that is depended
     176             :   /// on.  Otherwise, returns null.
     177             :   Instruction *getInst() const {
     178     5521796 :     switch (Value.getTag()) {
     179      901878 :     case Invalid:
     180     1803756 :       return Value.cast<Invalid>();
     181     1195099 :     case Clobber:
     182     5155184 :       return Value.cast<Clobber>();
     183      785478 :     case Def:
     184     1570956 :       return Value.cast<Def>();
     185             :     case Other:
     186             :       return nullptr;
     187             :     }
     188           0 :     llvm_unreachable("Unknown discriminant!");
     189             :   }
     190             : 
     191             :   bool operator==(const MemDepResult &M) const { return Value == M.Value; }
     192             :   bool operator!=(const MemDepResult &M) const { return Value != M.Value; }
     193             :   bool operator<(const MemDepResult &M) const { return Value < M.Value; }
     194             :   bool operator>(const MemDepResult &M) const { return Value > M.Value; }
     195             : 
     196             : private:
     197             :   friend class MemoryDependenceResults;
     198             : 
     199             :   /// Tests if this is a MemDepResult in its dirty/invalid. state.
     200     3289372 :   bool isDirty() const { return Value.is<Invalid>(); }
     201             : 
     202             :   static MemDepResult getDirty(Instruction *Inst) {
     203      180480 :     return MemDepResult(ValueTy::create<Invalid>(Inst));
     204             :   }
     205             : };
     206             : 
     207             : /// This is an entry in the NonLocalDepInfo cache.
     208             : ///
     209             : /// For each BasicBlock (the BB entry) it keeps a MemDepResult.
     210             : class NonLocalDepEntry {
     211             :   BasicBlock *BB;
     212             :   MemDepResult Result;
     213             : 
     214             : public:
     215             :   NonLocalDepEntry(BasicBlock *bb, MemDepResult result)
     216     1535134 :       : BB(bb), Result(result) {}
     217             : 
     218             :   // This is used for searches.
     219     2932072 :   NonLocalDepEntry(BasicBlock *bb) : BB(bb) {}
     220             : 
     221             :   // BB is the sort key, it can't be changed.
     222             :   BasicBlock *getBB() const { return BB; }
     223             : 
     224        8886 :   void setResult(const MemDepResult &R) { Result = R; }
     225             : 
     226           0 :   const MemDepResult &getResult() const { return Result; }
     227             : 
     228             :   bool operator<(const NonLocalDepEntry &RHS) const { return BB < RHS.BB; }
     229             : };
     230             : 
     231             : /// This is a result from a NonLocal dependence query.
     232             : ///
     233             : /// For each BasicBlock (the BB entry) it keeps a MemDepResult and the
     234             : /// (potentially phi translated) address that was live in the block.
     235             : class NonLocalDepResult {
     236             :   NonLocalDepEntry Entry;
     237             :   Value *Address;
     238             : 
     239             : public:
     240             :   NonLocalDepResult(BasicBlock *bb, MemDepResult result, Value *address)
     241     1144294 :       : Entry(bb, result), Address(address) {}
     242             : 
     243             :   // BB is the sort key, it can't be changed.
     244      476217 :   BasicBlock *getBB() const { return Entry.getBB(); }
     245             : 
     246             :   void setResult(const MemDepResult &R, Value *Addr) {
     247             :     Entry.setResult(R);
     248             :     Address = Addr;
     249             :   }
     250             : 
     251      734320 :   const MemDepResult &getResult() const { return Entry.getResult(); }
     252             : 
     253             :   /// Returns the address of this pointer in this block.
     254             :   ///
     255             :   /// This can be different than the address queried for the non-local result
     256             :   /// because of phi translation.  This returns null if the address was not
     257             :   /// available in a block (i.e. because phi translation failed) or if this is
     258             :   /// a cached result and that address was deleted.
     259             :   ///
     260             :   /// The address is always null for a non-local 'call' dependence.
     261             :   Value *getAddress() const { return Address; }
     262             : };
     263             : 
     264             : /// Provides a lazy, caching interface for making common memory aliasing
     265             : /// information queries, backed by LLVM's alias analysis passes.
     266             : ///
     267             : /// The dependency information returned is somewhat unusual, but is pragmatic.
     268             : /// If queried about a store or call that might modify memory, the analysis
     269             : /// will return the instruction[s] that may either load from that memory or
     270             : /// store to it.  If queried with a load or call that can never modify memory,
     271             : /// the analysis will return calls and stores that might modify the pointer,
     272             : /// but generally does not return loads unless a) they are volatile, or
     273             : /// b) they load from *must-aliased* pointers.  Returning a dependence on
     274             : /// must-alias'd pointers instead of all pointers interacts well with the
     275             : /// internal caching mechanism.
     276      934160 : class MemoryDependenceResults {
     277             :   // A map from instructions to their dependency.
     278             :   using LocalDepMapType = DenseMap<Instruction *, MemDepResult>;
     279             :   LocalDepMapType LocalDeps;
     280             : 
     281             : public:
     282             :   using NonLocalDepInfo = std::vector<NonLocalDepEntry>;
     283             : 
     284             : private:
     285             :   /// A pair<Value*, bool> where the bool is true if the dependence is a read
     286             :   /// only dependence, false if read/write.
     287             :   using ValueIsLoadPair = PointerIntPair<const Value *, 1, bool>;
     288             : 
     289             :   /// This pair is used when caching information for a block.
     290             :   ///
     291             :   /// If the pointer is null, the cache value is not a full query that starts
     292             :   /// at the specified block.  If non-null, the bool indicates whether or not
     293             :   /// the contents of the block was skipped.
     294             :   using BBSkipFirstBlockPair = PointerIntPair<BasicBlock *, 1, bool>;
     295             : 
     296             :   /// This record is the information kept for each (value, is load) pair.
     297     2003512 :   struct NonLocalPointerInfo {
     298             :     /// The pair of the block and the skip-first-block flag.
     299             :     BBSkipFirstBlockPair Pair;
     300             :     /// The results of the query for each relevant block.
     301             :     NonLocalDepInfo NonLocalDeps;
     302             :     /// The maximum size of the dereferences of the pointer.
     303             :     ///
     304             :     /// May be UnknownSize if the sizes are unknown.
     305             :     uint64_t Size = MemoryLocation::UnknownSize;
     306             :     /// The AA tags associated with dereferences of the pointer.
     307             :     ///
     308             :     /// The members may be null if there are no tags or conflicting tags.
     309             :     AAMDNodes AATags;
     310             : 
     311     1171728 :     NonLocalPointerInfo() = default;
     312             :   };
     313             : 
     314             :   /// Cache storing single nonlocal def for the instruction.
     315             :   /// It is set when nonlocal def would be found in function returning only
     316             :   /// local dependencies.
     317             :   DenseMap<Instruction *, NonLocalDepResult> NonLocalDefsCache;
     318             : 
     319             :   /// This map stores the cached results of doing a pointer lookup at the
     320             :   /// bottom of a block.
     321             :   ///
     322             :   /// The key of this map is the pointer+isload bit, the value is a list of
     323             :   /// <bb->result> mappings.
     324             :   using CachedNonLocalPointerInfo =
     325             :       DenseMap<ValueIsLoadPair, NonLocalPointerInfo>;
     326             :   CachedNonLocalPointerInfo NonLocalPointerDeps;
     327             : 
     328             :   // A map from instructions to their non-local pointer dependencies.
     329             :   using ReverseNonLocalPtrDepTy =
     330             :       DenseMap<Instruction *, SmallPtrSet<ValueIsLoadPair, 4>>;
     331             :   ReverseNonLocalPtrDepTy ReverseNonLocalPtrDeps;
     332             : 
     333             :   /// This is the instruction we keep for each cached access that we have for
     334             :   /// an instruction.
     335             :   ///
     336             :   /// The pointer is an owning pointer and the bool indicates whether we have
     337             :   /// any dirty bits in the set.
     338             :   using PerInstNLInfo = std::pair<NonLocalDepInfo, bool>;
     339             : 
     340             :   // A map from instructions to their non-local dependencies.
     341             :   using NonLocalDepMapType = DenseMap<Instruction *, PerInstNLInfo>;
     342             : 
     343             :   NonLocalDepMapType NonLocalDeps;
     344             : 
     345             :   // A reverse mapping from dependencies to the dependees.  This is
     346             :   // used when removing instructions to keep the cache coherent.
     347             :   using ReverseDepMapType =
     348             :       DenseMap<Instruction *, SmallPtrSet<Instruction *, 4>>;
     349             :   ReverseDepMapType ReverseLocalDeps;
     350             : 
     351             :   // A reverse mapping from dependencies to the non-local dependees.
     352             :   ReverseDepMapType ReverseNonLocalDeps;
     353             : 
     354             :   /// Current AA implementation, just a cache.
     355             :   AliasAnalysis &AA;
     356             :   AssumptionCache &AC;
     357             :   const TargetLibraryInfo &TLI;
     358             :   DominatorTree &DT;
     359             :   PredIteratorCache PredCache;
     360             : 
     361             : public:
     362      115750 :   MemoryDependenceResults(AliasAnalysis &AA, AssumptionCache &AC,
     363             :                           const TargetLibraryInfo &TLI,
     364             :                           DominatorTree &DT)
     365      926000 :       : AA(AA), AC(AC), TLI(TLI), DT(DT) {}
     366             : 
     367             :   /// Handle invalidation in the new PM.
     368             :   bool invalidate(Function &F, const PreservedAnalyses &PA,
     369             :                   FunctionAnalysisManager::Invalidator &Inv);
     370             : 
     371             :   /// Some methods limit the number of instructions they will examine.
     372             :   /// The return value of this method is the default limit that will be
     373             :   /// used if no limit is explicitly passed in.
     374             :   unsigned getDefaultBlockScanLimit() const;
     375             : 
     376             :   /// Returns the instruction on which a memory operation depends.
     377             :   ///
     378             :   /// See the class comment for more details. It is illegal to call this on
     379             :   /// non-memory instructions.
     380             :   MemDepResult getDependency(Instruction *QueryInst);
     381             : 
     382             :   /// Perform a full dependency query for the specified call, returning the set
     383             :   /// of blocks that the value is potentially live across.
     384             :   ///
     385             :   /// The returned set of results will include a "NonLocal" result for all
     386             :   /// blocks where the value is live across.
     387             :   ///
     388             :   /// This method assumes the instruction returns a "NonLocal" dependency
     389             :   /// within its own block.
     390             :   ///
     391             :   /// This returns a reference to an internal data structure that may be
     392             :   /// invalidated on the next non-local query or when an instruction is
     393             :   /// removed.  Clients must copy this data if they want it around longer than
     394             :   /// that.
     395             :   const NonLocalDepInfo &getNonLocalCallDependency(CallSite QueryCS);
     396             : 
     397             :   /// Perform a full dependency query for an access to the QueryInst's
     398             :   /// specified memory location, returning the set of instructions that either
     399             :   /// define or clobber the value.
     400             :   ///
     401             :   /// Warning: For a volatile query instruction, the dependencies will be
     402             :   /// accurate, and thus usable for reordering, but it is never legal to
     403             :   /// remove the query instruction.
     404             :   ///
     405             :   /// This method assumes the pointer has a "NonLocal" dependency within
     406             :   /// QueryInst's parent basic block.
     407             :   void getNonLocalPointerDependency(Instruction *QueryInst,
     408             :                                     SmallVectorImpl<NonLocalDepResult> &Result);
     409             : 
     410             :   /// Removes an instruction from the dependence analysis, updating the
     411             :   /// dependence of instructions that previously depended on it.
     412             :   void removeInstruction(Instruction *InstToRemove);
     413             : 
     414             :   /// Invalidates cached information about the specified pointer, because it
     415             :   /// may be too conservative in memdep.
     416             :   ///
     417             :   /// This is an optional call that can be used when the client detects an
     418             :   /// equivalence between the pointer and some other value and replaces the
     419             :   /// other value with ptr. This can make Ptr available in more places that
     420             :   /// cached info does not necessarily keep.
     421             :   void invalidateCachedPointerInfo(Value *Ptr);
     422             : 
     423             :   /// Clears the PredIteratorCache info.
     424             :   ///
     425             :   /// This needs to be done when the CFG changes, e.g., due to splitting
     426             :   /// critical edges.
     427             :   void invalidateCachedPredecessors();
     428             : 
     429             :   /// Returns the instruction on which a memory location depends.
     430             :   ///
     431             :   /// If isLoad is true, this routine ignores may-aliases with read-only
     432             :   /// operations.  If isLoad is false, this routine ignores may-aliases
     433             :   /// with reads from read-only locations. If possible, pass the query
     434             :   /// instruction as well; this function may take advantage of the metadata
     435             :   /// annotated to the query instruction to refine the result. \p Limit
     436             :   /// can be used to set the maximum number of instructions that will be
     437             :   /// examined to find the pointer dependency. On return, it will be set to
     438             :   /// the number of instructions left to examine. If a null pointer is passed
     439             :   /// in, the limit will default to the value of -memdep-block-scan-limit.
     440             :   ///
     441             :   /// Note that this is an uncached query, and thus may be inefficient.
     442             :   MemDepResult getPointerDependencyFrom(const MemoryLocation &Loc, bool isLoad,
     443             :                                         BasicBlock::iterator ScanIt,
     444             :                                         BasicBlock *BB,
     445             :                                         Instruction *QueryInst = nullptr,
     446             :                                         unsigned *Limit = nullptr);
     447             : 
     448             :   MemDepResult getSimplePointerDependencyFrom(const MemoryLocation &MemLoc,
     449             :                                               bool isLoad,
     450             :                                               BasicBlock::iterator ScanIt,
     451             :                                               BasicBlock *BB,
     452             :                                               Instruction *QueryInst,
     453             :                                               unsigned *Limit = nullptr);
     454             : 
     455             :   /// This analysis looks for other loads and stores with invariant.group
     456             :   /// metadata and the same pointer operand. Returns Unknown if it does not
     457             :   /// find anything, and Def if it can be assumed that 2 instructions load or
     458             :   /// store the same value and NonLocal which indicate that non-local Def was
     459             :   /// found, which can be retrieved by calling getNonLocalPointerDependency
     460             :   /// with the same queried instruction.
     461             :   MemDepResult getInvariantGroupPointerDependency(LoadInst *LI, BasicBlock *BB);
     462             : 
     463             :   /// Looks at a memory location for a load (specified by MemLocBase, Offs, and
     464             :   /// Size) and compares it against a load.
     465             :   ///
     466             :   /// If the specified load could be safely widened to a larger integer load
     467             :   /// that is 1) still efficient, 2) safe for the target, and 3) would provide
     468             :   /// the specified memory location value, then this function returns the size
     469             :   /// in bytes of the load width to use.  If not, this returns zero.
     470             :   static unsigned getLoadLoadClobberFullWidthSize(const Value *MemLocBase,
     471             :                                                   int64_t MemLocOffs,
     472             :                                                   unsigned MemLocSize,
     473             :                                                   const LoadInst *LI);
     474             : 
     475             :   /// Release memory in caches.
     476             :   void releaseMemory();
     477             : 
     478             : private:
     479             :   MemDepResult getCallSiteDependencyFrom(CallSite C, bool isReadOnlyCall,
     480             :                                          BasicBlock::iterator ScanIt,
     481             :                                          BasicBlock *BB);
     482             :   bool getNonLocalPointerDepFromBB(Instruction *QueryInst,
     483             :                                    const PHITransAddr &Pointer,
     484             :                                    const MemoryLocation &Loc, bool isLoad,
     485             :                                    BasicBlock *BB,
     486             :                                    SmallVectorImpl<NonLocalDepResult> &Result,
     487             :                                    DenseMap<BasicBlock *, Value *> &Visited,
     488             :                                    bool SkipFirstBlock = false);
     489             :   MemDepResult GetNonLocalInfoForBlock(Instruction *QueryInst,
     490             :                                        const MemoryLocation &Loc, bool isLoad,
     491             :                                        BasicBlock *BB, NonLocalDepInfo *Cache,
     492             :                                        unsigned NumSortedEntries);
     493             : 
     494             :   void RemoveCachedNonLocalPointerDependencies(ValueIsLoadPair P);
     495             : 
     496             :   void verifyRemoved(Instruction *Inst) const;
     497             : };
     498             : 
     499             : /// An analysis that produces \c MemoryDependenceResults for a function.
     500             : ///
     501             : /// This is essentially a no-op because the results are computed entirely
     502             : /// lazily.
     503             : class MemoryDependenceAnalysis
     504             :     : public AnalysisInfoMixin<MemoryDependenceAnalysis> {
     505             :   friend AnalysisInfoMixin<MemoryDependenceAnalysis>;
     506             : 
     507             :   static AnalysisKey Key;
     508             : 
     509             : public:
     510             :   using Result = MemoryDependenceResults;
     511             : 
     512             :   MemoryDependenceResults run(Function &F, FunctionAnalysisManager &AM);
     513             : };
     514             : 
     515             : /// A wrapper analysis pass for the legacy pass manager that exposes a \c
     516             : /// MemoryDepnedenceResults instance.
     517       18984 : class MemoryDependenceWrapperPass : public FunctionPass {
     518             :   Optional<MemoryDependenceResults> MemDep;
     519             : 
     520             : public:
     521             :   static char ID;
     522             : 
     523             :   MemoryDependenceWrapperPass();
     524             :   ~MemoryDependenceWrapperPass() override;
     525             : 
     526             :   /// Pass Implementation stuff.  This doesn't do any analysis eagerly.
     527             :   bool runOnFunction(Function &) override;
     528             : 
     529             :   /// Clean up memory in between runs
     530             :   void releaseMemory() override;
     531             : 
     532             :   /// Does not modify anything.  It uses Value Numbering and Alias Analysis.
     533             :   void getAnalysisUsage(AnalysisUsage &AU) const override;
     534             : 
     535      231196 :   MemoryDependenceResults &getMemDep() { return *MemDep; }
     536             : };
     537             : 
     538             : } // end namespace llvm
     539             : 
     540             : #endif // LLVM_ANALYSIS_MEMORYDEPENDENCEANALYSIS_H

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