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