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//===- llvm/Analysis/MemoryDependenceAnalysis.h - Memory Deps --*- C++ -*-===//
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// The LLVM Compiler Infrastructure
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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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// This file defines the MemoryDependenceAnalysis analysis pass.
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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/Support/ValueHandle.h"
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#include "llvm/Analysis/AliasAnalysis.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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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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/// Invalid - Clients of MemDep never see this.
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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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/// There are several cases that may be interesting here:
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/// 1. Loads are clobbered by may-alias stores.
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/// 2. Loads are considered clobbered by partially-aliased loads. The
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/// client may choose to analyze deeper into these cases.
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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 or memory use intrinsics with identical callees
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/// and no intervening clobbers. No validation is done that the
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/// operands to the calls are the same.
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/// Other - This marker indicates that the query has no known dependency
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/// in the specified block. More detailed state info is encoded in the
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/// upper part of the pair (i.e. the Instruction*)
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/// If DepType is "Other", the upper part of the pair
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/// (i.e. the Instruction* part) is instead used to encode more detailed
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/// type information as follows
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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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/// NonFuncLocal - This marker indicates that the query has no
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/// dependency in the specified function.
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/// Unknown - This marker indicates that the query dependency
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typedef PointerIntPair<Instruction*, 2, DepType> PairTy;
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explicit MemDepResult(PairTy V) : Value(V) {}
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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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assert(Inst && "Def requires inst");
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return MemDepResult(PairTy(Inst, Def));
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static MemDepResult getClobber(Instruction *Inst) {
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assert(Inst && "Clobber requires inst");
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return MemDepResult(PairTy(Inst, Clobber));
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static MemDepResult getNonLocal() {
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PairTy(reinterpret_cast<Instruction*>(NonLocal), Other));
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static MemDepResult getNonFuncLocal() {
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PairTy(reinterpret_cast<Instruction*>(NonFuncLocal), Other));
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static MemDepResult getUnknown() {
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PairTy(reinterpret_cast<Instruction*>(Unknown), Other));
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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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bool isNonLocal() const {
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return Value.getInt() == Other
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&& Value.getPointer() == reinterpret_cast<Instruction*>(NonLocal);
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/// isNonFuncLocal - Return true if this MemDepResult represents a query
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/// that is transparent to the start of the function.
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bool isNonFuncLocal() const {
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return Value.getInt() == Other
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&& Value.getPointer() == reinterpret_cast<Instruction*>(NonFuncLocal);
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/// isUnknown - Return true if this MemDepResult represents a query which
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/// cannot and/or will not be computed.
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bool isUnknown() const {
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return Value.getInt() == Other
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&& Value.getPointer() == reinterpret_cast<Instruction*>(Unknown);
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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 {
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if (Value.getInt() == Other) return NULL;
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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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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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/// 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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/// isDirty - Return true if this is a MemDepResult in its dirty/invalid.
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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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/// NonLocalDepEntry - This is an entry in the NonLocalDepInfo cache. For
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/// each BasicBlock (the BB entry) it keeps a MemDepResult.
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class NonLocalDepEntry {
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NonLocalDepEntry(BasicBlock *bb, MemDepResult result)
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: BB(bb), Result(result) {}
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// This is used for searches.
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NonLocalDepEntry(BasicBlock *bb) : BB(bb) {}
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// BB is the sort key, it can't be changed.
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BasicBlock *getBB() const { return BB; }
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void setResult(const MemDepResult &R) { Result = R; }
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const MemDepResult &getResult() const { return Result; }
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bool operator<(const NonLocalDepEntry &RHS) const {
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/// NonLocalDepResult - This is a result from a NonLocal dependence query.
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/// For each BasicBlock (the BB entry) it keeps a MemDepResult and the
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/// (potentially phi translated) address that was live in the block.
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class NonLocalDepResult {
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NonLocalDepEntry Entry;
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NonLocalDepResult(BasicBlock *bb, MemDepResult result, Value *address)
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: Entry(bb, result), Address(address) {}
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// BB is the sort key, it can't be changed.
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BasicBlock *getBB() const { return Entry.getBB(); }
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void setResult(const MemDepResult &R, Value *Addr) {
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const MemDepResult &getResult() const { return Entry.getResult(); }
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/// getAddress - Return the address of this pointer in this block. This can
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/// be different than the address queried for the non-local result because
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/// of phi translation. This returns null if the address was not available
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/// in a block (i.e. because phi translation failed) or if this is a cached
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/// result and that address was deleted.
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/// The address is always null for a non-local 'call' dependence.
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Value *getAddress() const { return Address; }
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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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/// 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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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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typedef std::vector<NonLocalDepEntry> NonLocalDepInfo;
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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<const 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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/// NonLocalPointerInfo - This record is the information kept for each
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/// (value, is load) pair.
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struct NonLocalPointerInfo {
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/// Pair - The pair of the block and the skip-first-block flag.
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BBSkipFirstBlockPair Pair;
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/// NonLocalDeps - The results of the query for each relevant block.
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NonLocalDepInfo NonLocalDeps;
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/// Size - The maximum size of the dereferences of the
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/// pointer. May be UnknownSize if the sizes are unknown.
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/// TBAATag - The TBAA tag associated with dereferences of the
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/// pointer. May be null if there are no tags or conflicting tags.
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const MDNode *TBAATag;
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NonLocalPointerInfo() : Size(AliasAnalysis::UnknownSize), TBAATag(0) {}
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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,
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NonLocalPointerInfo> 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 from 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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OwningPtr<PredIteratorCache> PredCache;
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MemoryDependenceAnalysis();
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~MemoryDependenceAnalysis();
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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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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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/// This method assumes the instruction returns a "NonLocal" dependency
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/// within its own block.
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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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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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/// This method assumes the pointer has a "NonLocal" dependency within BB.
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void getNonLocalPointerDependency(const AliasAnalysis::Location &Loc,
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bool isLoad, BasicBlock *BB,
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SmallVectorImpl<NonLocalDepResult> &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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/// invalidateCachedPredecessors - Clear the PredIteratorCache info.
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/// This needs to be done when the CFG changes, e.g., due to splitting
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void invalidateCachedPredecessors();
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/// getPointerDependencyFrom - Return the instruction on which a memory
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/// location depends. If isLoad is true, this routine ignores may-aliases
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/// with read-only operations. If isLoad is false, this routine ignores
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/// may-aliases with reads from read-only locations.
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/// Note that this is an uncached query, and thus may be inefficient.
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MemDepResult getPointerDependencyFrom(const AliasAnalysis::Location &Loc,
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BasicBlock::iterator ScanIt,
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/// getLoadLoadClobberFullWidthSize - This is a little bit of analysis that
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/// looks at a memory location for a load (specified by MemLocBase, Offs,
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/// and Size) and compares it against a load. If the specified load could
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/// be safely widened to a larger integer load that is 1) still efficient,
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/// 2) safe for the target, and 3) would provide the specified memory
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/// location value, then this function returns the size in bytes of the
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/// load width to use. If not, this returns zero.
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static unsigned getLoadLoadClobberFullWidthSize(const Value *MemLocBase,
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const TargetData &TD);
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MemDepResult getCallSiteDependencyFrom(CallSite C, bool isReadOnlyCall,
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BasicBlock::iterator ScanIt,
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bool getNonLocalPointerDepFromBB(const PHITransAddr &Pointer,
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const AliasAnalysis::Location &Loc,
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bool isLoad, BasicBlock *BB,
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SmallVectorImpl<NonLocalDepResult> &Result,
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DenseMap<BasicBlock*, Value*> &Visited,
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bool SkipFirstBlock = false);
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MemDepResult GetNonLocalInfoForBlock(const AliasAnalysis::Location &Loc,
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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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AliasAnalysis::ModRefResult
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getModRefInfo(const Instruction *Inst, const AliasAnalysis::Location &Loc);
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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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} // End llvm namespace