//
//===----------------------------------------------------------------------===//
//
-// This file defines an analysis that determines, for a given memory operation,
-// what preceding memory operations it depends on. It builds on alias analysis
-// information, and tries to provide a lazy, caching interface to a common kind
-// of alias information query.
+// This file defines the MemoryDependenceAnalysis analysis pass.
//
//===----------------------------------------------------------------------===//
#ifndef LLVM_ANALYSIS_MEMORY_DEPENDENCE_H
#define LLVM_ANALYSIS_MEMORY_DEPENDENCE_H
+#include "llvm/BasicBlock.h"
#include "llvm/Pass.h"
-#include "llvm/Support/CallSite.h"
#include "llvm/ADT/DenseMap.h"
#include "llvm/ADT/SmallPtrSet.h"
-#include "llvm/Support/Compiler.h"
+#include "llvm/ADT/OwningPtr.h"
+#include "llvm/ADT/PointerIntPair.h"
namespace llvm {
+ class Function;
+ class FunctionPass;
+ class Instruction;
+ class CallSite;
+ class AliasAnalysis;
+ class TargetData;
+ class MemoryDependenceAnalysis;
+ class PredIteratorCache;
+
+ /// MemDepResult - A memory dependence query can return one of three different
+ /// answers, described below.
+ class MemDepResult {
+ enum DepType {
+ /// Invalid - Clients of MemDep never see this.
+ Invalid = 0,
+
+ /// Clobber - This is a dependence on the specified instruction which
+ /// clobbers the desired value. The pointer member of the MemDepResult
+ /// pair holds the instruction that clobbers the memory. For example,
+ /// this occurs when we see a may-aliased store to the memory location we
+ /// care about.
+ Clobber,
-class Function;
-class FunctionPass;
-class Instruction;
+ /// Def - This is a dependence on the specified instruction which
+ /// defines/produces the desired memory location. The pointer member of
+ /// the MemDepResult pair holds the instruction that defines the memory.
+ /// Cases of interest:
+ /// 1. This could be a load or store for dependence queries on
+ /// load/store. The value loaded or stored is the produced value.
+ /// Note that the pointer operand may be different than that of the
+ /// queried pointer due to must aliases and phi translation. Note
+ /// that the def may not be the same type as the query, the pointers
+ /// may just be must aliases.
+ /// 2. For loads and stores, this could be an allocation instruction. In
+ /// this case, the load is loading an undef value or a store is the
+ /// first store to (that part of) the allocation.
+ /// 3. Dependence queries on calls return Def only when they are
+ /// readonly calls with identical callees and no intervening
+ /// clobbers. No validation is done that the operands to the calls
+ /// are the same.
+ Def,
+
+ /// NonLocal - This marker indicates that the query has no dependency in
+ /// the specified block. To find out more, the client should query other
+ /// predecessor blocks.
+ NonLocal
+ };
+ typedef PointerIntPair<Instruction*, 2, DepType> PairTy;
+ PairTy Value;
+ explicit MemDepResult(PairTy V) : Value(V) {}
+ public:
+ MemDepResult() : Value(0, Invalid) {}
+
+ /// get methods: These are static ctor methods for creating various
+ /// MemDepResult kinds.
+ static MemDepResult getDef(Instruction *Inst) {
+ return MemDepResult(PairTy(Inst, Def));
+ }
+ static MemDepResult getClobber(Instruction *Inst) {
+ return MemDepResult(PairTy(Inst, Clobber));
+ }
+ static MemDepResult getNonLocal() {
+ return MemDepResult(PairTy(0, NonLocal));
+ }
-class MemoryDependenceAnalysis : public FunctionPass {
- private:
- // A map from instructions to their dependency, with a boolean
- // flags for whether this mapping is confirmed or not
- typedef DenseMap<Instruction*, std::pair<Instruction*, bool> >
- depMapType;
- depMapType depGraphLocal;
+ /// isClobber - Return true if this MemDepResult represents a query that is
+ /// a instruction clobber dependency.
+ bool isClobber() const { return Value.getInt() == Clobber; }
- // A map from instructions to their non-local dependencies.
- typedef DenseMap<Instruction*, DenseMap<BasicBlock*, Value*> >
- nonLocalDepMapType;
- nonLocalDepMapType depGraphNonLocal;
+ /// isDef - Return true if this MemDepResult represents a query that is
+ /// a instruction definition dependency.
+ bool isDef() const { return Value.getInt() == Def; }
- // A reverse mapping form dependencies to the dependees. This is
- // used when removing instructions to keep the cache coherent.
- typedef DenseMap<Value*, SmallPtrSet<Instruction*, 4> >
- reverseDepMapType;
- reverseDepMapType reverseDep;
+ /// isNonLocal - Return true if this MemDepResult represents a query that
+ /// is transparent to the start of the block, but where a non-local hasn't
+ /// been done.
+ bool isNonLocal() const { return Value.getInt() == NonLocal; }
- // A reverse mapping form dependencies to the non-local dependees.
- reverseDepMapType reverseDepNonLocal;
+ /// getInst() - If this is a normal dependency, return the instruction that
+ /// is depended on. Otherwise, return null.
+ Instruction *getInst() const { return Value.getPointer(); }
+
+ bool operator==(const MemDepResult &M) const { return Value == M.Value; }
+ bool operator!=(const MemDepResult &M) const { return Value != M.Value; }
+ bool operator<(const MemDepResult &M) const { return Value < M.Value; }
+ bool operator>(const MemDepResult &M) const { return Value > M.Value; }
+ private:
+ friend class MemoryDependenceAnalysis;
+ /// Dirty - Entries with this marker occur in a LocalDeps map or
+ /// NonLocalDeps map when the instruction they previously referenced was
+ /// removed from MemDep. In either case, the entry may include an
+ /// instruction pointer. If so, the pointer is an instruction in the
+ /// block where scanning can start from, saving some work.
+ ///
+ /// In a default-constructed MemDepResult object, the type will be Dirty
+ /// and the instruction pointer will be null.
+ ///
+
+ /// isDirty - Return true if this is a MemDepResult in its dirty/invalid.
+ /// state.
+ bool isDirty() const { return Value.getInt() == Invalid; }
+ static MemDepResult getDirty(Instruction *Inst) {
+ return MemDepResult(PairTy(Inst, Invalid));
+ }
+ };
+
+ /// MemoryDependenceAnalysis - This is an analysis that determines, for a
+ /// given memory operation, what preceding memory operations it depends on.
+ /// It builds on alias analysis information, and tries to provide a lazy,
+ /// caching interface to a common kind of alias information query.
+ ///
+ /// The dependency information returned is somewhat unusual, but is pragmatic.
+ /// If queried about a store or call that might modify memory, the analysis
+ /// will return the instruction[s] that may either load from that memory or
+ /// store to it. If queried with a load or call that can never modify memory,
+ /// the analysis will return calls and stores that might modify the pointer,
+ /// but generally does not return loads unless a) they are volatile, or
+ /// b) they load from *must-aliased* pointers. Returning a dependence on
+ /// must-alias'd pointers instead of all pointers interacts well with the
+ /// internal caching mechanism.
+ ///
+ class MemoryDependenceAnalysis : public FunctionPass {
+ // A map from instructions to their dependency.
+ typedef DenseMap<Instruction*, MemDepResult> LocalDepMapType;
+ LocalDepMapType LocalDeps;
+
public:
- void ping(Instruction* D);
+ typedef std::pair<BasicBlock*, MemDepResult> NonLocalDepEntry;
+ typedef std::vector<NonLocalDepEntry> NonLocalDepInfo;
+ private:
+ /// ValueIsLoadPair - This is a pair<Value*, bool> where the bool is true if
+ /// the dependence is a read only dependence, false if read/write.
+ typedef PointerIntPair<Value*, 1, bool> ValueIsLoadPair;
+
+ /// BBSkipFirstBlockPair - This pair is used when caching information for a
+ /// block. If the pointer is null, the cache value is not a full query that
+ /// starts at the specified block. If non-null, the bool indicates whether
+ /// or not the contents of the block was skipped.
+ typedef PointerIntPair<BasicBlock*, 1, bool> BBSkipFirstBlockPair;
+
+ /// CachedNonLocalPointerInfo - This map stores the cached results of doing
+ /// a pointer lookup at the bottom of a block. The key of this map is the
+ /// pointer+isload bit, the value is a list of <bb->result> mappings.
+ typedef DenseMap<ValueIsLoadPair, std::pair<BBSkipFirstBlockPair,
+ NonLocalDepInfo> > CachedNonLocalPointerInfo;
+ CachedNonLocalPointerInfo NonLocalPointerDeps;
+
+ // A map from instructions to their non-local pointer dependencies.
+ typedef DenseMap<Instruction*,
+ SmallPtrSet<ValueIsLoadPair, 4> > ReverseNonLocalPtrDepTy;
+ ReverseNonLocalPtrDepTy ReverseNonLocalPtrDeps;
- // Special marker indicating that the query has no dependency
- // in the specified block.
- static Instruction* const NonLocal;
- // Special marker indicating that the query has no dependency at all
- static Instruction* const None;
+ /// PerInstNLInfo - This is the instruction we keep for each cached access
+ /// that we have for an instruction. The pointer is an owning pointer and
+ /// the bool indicates whether we have any dirty bits in the set.
+ typedef std::pair<NonLocalDepInfo, bool> PerInstNLInfo;
+ // A map from instructions to their non-local dependencies.
+ typedef DenseMap<Instruction*, PerInstNLInfo> NonLocalDepMapType;
+
+ NonLocalDepMapType NonLocalDeps;
- // Special marker indicating a dirty cache entry
- static Instruction* const Dirty;
+ // A reverse mapping from dependencies to the dependees. This is
+ // used when removing instructions to keep the cache coherent.
+ typedef DenseMap<Instruction*,
+ SmallPtrSet<Instruction*, 4> > ReverseDepMapType;
+ ReverseDepMapType ReverseLocalDeps;
- static char ID; // Class identification, replacement for typeinfo
- MemoryDependenceAnalysis() : FunctionPass((intptr_t)&ID) {}
-
- /// isAnalysis - Return true if this pass is implementing an analysis pass.
- virtual bool isAnalysis() const { return true; }
+ // A reverse mapping form dependencies to the non-local dependees.
+ ReverseDepMapType ReverseNonLocalDeps;
+
+ /// Current AA implementation, just a cache.
+ AliasAnalysis *AA;
+ TargetData *TD;
+ OwningPtr<PredIteratorCache> PredCache;
+ public:
+ MemoryDependenceAnalysis();
+ ~MemoryDependenceAnalysis();
+ static char ID;
- /// Pass Implementation stuff. This doesn't do any analysis.
- ///
- bool runOnFunction(Function &) {return false; }
+ /// Pass Implementation stuff. This doesn't do any analysis eagerly.
+ bool runOnFunction(Function &);
/// Clean up memory in between runs
- void releaseMemory() {
- depGraphLocal.clear();
- depGraphNonLocal.clear();
- reverseDep.clear();
- reverseDepNonLocal.clear();
- }
-
+ void releaseMemory();
+
/// getAnalysisUsage - Does not modify anything. It uses Value Numbering
/// and Alias Analysis.
///
virtual void getAnalysisUsage(AnalysisUsage &AU) const;
/// getDependency - Return the instruction on which a memory operation
- /// depends, starting with start.
- Instruction* getDependency(Instruction* query, Instruction* start = 0,
- BasicBlock* block = 0);
+ /// depends. See the class comment for more details. It is illegal to call
+ /// this on non-memory instructions.
+ MemDepResult getDependency(Instruction *QueryInst);
+
+ /// getNonLocalCallDependency - Perform a full dependency query for the
+ /// specified call, returning the set of blocks that the value is
+ /// potentially live across. The returned set of results will include a
+ /// "NonLocal" result for all blocks where the value is live across.
+ ///
+ /// This method assumes the instruction returns a "NonLocal" dependency
+ /// within its own block.
+ ///
+ /// This returns a reference to an internal data structure that may be
+ /// invalidated on the next non-local query or when an instruction is
+ /// removed. Clients must copy this data if they want it around longer than
+ /// that.
+ const NonLocalDepInfo &getNonLocalCallDependency(CallSite QueryCS);
- /// getNonLocalDependency - Fills the passed-in map with the non-local
- /// dependencies of the queries. The map will contain NonLocal for
- /// blocks between the query and its dependencies.
- void getNonLocalDependency(Instruction* query,
- DenseMap<BasicBlock*, Value*>& resp);
+
+ /// getNonLocalPointerDependency - Perform a full dependency query for an
+ /// access to the specified (non-volatile) memory location, returning the
+ /// set of instructions that either define or clobber the value.
+ ///
+ /// This method assumes the pointer has a "NonLocal" dependency within BB.
+ void getNonLocalPointerDependency(Value *Pointer, bool isLoad,
+ BasicBlock *BB,
+ SmallVectorImpl<NonLocalDepEntry> &Result);
/// removeInstruction - Remove an instruction from the dependence analysis,
/// updating the dependence of instructions that previously depended on it.
- void removeInstruction(Instruction* rem);
+ void removeInstruction(Instruction *InstToRemove);
- /// dropInstruction - Remove an instruction from the analysis, making
- /// absolutely conservative assumptions when updating the cache. This is
- /// useful, for example when an instruction is changed rather than removed.
- void dropInstruction(Instruction* drop);
+ /// invalidateCachedPointerInfo - This method is used to invalidate cached
+ /// information about the specified pointer, because it may be too
+ /// conservative in memdep. This is an optional call that can be used when
+ /// the client detects an equivalence between the pointer and some other
+ /// value and replaces the other value with ptr. This can make Ptr available
+ /// in more places that cached info does not necessarily keep.
+ void invalidateCachedPointerInfo(Value *Ptr);
private:
- Instruction* getCallSiteDependency(CallSite C, Instruction* start,
- BasicBlock* block);
- void nonLocalHelper(Instruction* query, BasicBlock* block,
- DenseMap<BasicBlock*, Value*>& resp);
+ MemDepResult getPointerDependencyFrom(Value *Pointer, uint64_t MemSize,
+ bool isLoad,
+ BasicBlock::iterator ScanIt,
+ BasicBlock *BB);
+ MemDepResult getCallSiteDependencyFrom(CallSite C, bool isReadOnlyCall,
+ BasicBlock::iterator ScanIt,
+ BasicBlock *BB);
+ bool getNonLocalPointerDepFromBB(Value *Pointer, uint64_t Size,
+ bool isLoad, BasicBlock *BB,
+ SmallVectorImpl<NonLocalDepEntry> &Result,
+ DenseMap<BasicBlock*, Value*> &Visited,
+ bool SkipFirstBlock = false);
+ MemDepResult GetNonLocalInfoForBlock(Value *Pointer, uint64_t PointeeSize,
+ bool isLoad, BasicBlock *BB,
+ NonLocalDepInfo *Cache,
+ unsigned NumSortedEntries);
+
+ void RemoveCachedNonLocalPointerDependencies(ValueIsLoadPair P);
+
+ /// verifyRemoved - Verify that the specified instruction does not occur
+ /// in our internal data structures.
+ void verifyRemoved(Instruction *Inst) const;
+
};
} // End llvm namespace
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