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llvm-6502/include/llvm/Analysis/MemoryDependenceAnalysis.h
Dan Gohman 81acc554b9 Fix a typo in a comment.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@77715 91177308-0d34-0410-b5e6-96231b3b80d8
2009-07-31 19:26:54 +00:00

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//===- llvm/Analysis/MemoryDependenceAnalysis.h - Memory Deps --*- C++ -*-===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// 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/ADT/DenseMap.h"
#include "llvm/ADT/SmallPtrSet.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,
/// 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));
}
/// isClobber - Return true if this MemDepResult represents a query that is
/// a instruction clobber dependency.
bool isClobber() const { return Value.getInt() == Clobber; }
/// isDef - Return true if this MemDepResult represents a query that is
/// a instruction definition dependency.
bool isDef() const { return Value.getInt() == Def; }
/// 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; }
/// 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:
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;
/// 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;
// 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;
// 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 eagerly.
bool runOnFunction(Function &);
/// Clean up memory in between runs
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. 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);
/// 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 *InstToRemove);
/// 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:
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
#endif