llvm-6502/include/llvm/Analysis/MemoryDependenceAnalysis.h
Shuxin Yang 985dac6579 Memory Dependence Analysis (not mem-dep test) take advantage of "invariant.load" metadata.
The "invariant.load" metadata indicates the memory unit being accessed is immutable.
A load annotated with this metadata can be moved across any store.

As I am not sure if it is legal to move such loads across barrier/fence, this
change dose not allow such transformation.

rdar://11311484

Thank Arnold for code review.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@176562 91177308-0d34-0410-b5e6-96231b3b80d8
2013-03-06 17:48:48 +00:00

446 lines
19 KiB
C++

//===- 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_MEMORYDEPENDENCEANALYSIS_H
#define LLVM_ANALYSIS_MEMORYDEPENDENCEANALYSIS_H
#include "llvm/ADT/DenseMap.h"
#include "llvm/ADT/OwningPtr.h"
#include "llvm/ADT/PointerIntPair.h"
#include "llvm/ADT/SmallPtrSet.h"
#include "llvm/Analysis/AliasAnalysis.h"
#include "llvm/IR/BasicBlock.h"
#include "llvm/Pass.h"
#include "llvm/Support/ValueHandle.h"
namespace llvm {
class Function;
class FunctionPass;
class Instruction;
class CallSite;
class AliasAnalysis;
class DataLayout;
class MemoryDependenceAnalysis;
class PredIteratorCache;
class DominatorTree;
class PHITransAddr;
/// 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.
///
/// There are several cases that may be interesting here:
/// 1. Loads are clobbered by may-alias stores.
/// 2. Loads are considered clobbered by partially-aliased loads. The
/// client may choose to analyze deeper into these cases.
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 or memory use intrinsics with identical callees
/// and no intervening clobbers. No validation is done that the
/// operands to the calls are the same.
Def,
/// Other - This marker indicates that the query has no known dependency
/// in the specified block. More detailed state info is encoded in the
/// upper part of the pair (i.e. the Instruction*)
Other
};
/// If DepType is "Other", the upper part of the pair
/// (i.e. the Instruction* part) is instead used to encode more detailed
/// type information as follows
enum OtherType {
/// 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 = 0x4,
/// NonFuncLocal - This marker indicates that the query has no
/// dependency in the specified function.
NonFuncLocal = 0x8,
/// Unknown - This marker indicates that the query dependency
/// is unknown.
Unknown = 0xc
};
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) {
assert(Inst && "Def requires inst");
return MemDepResult(PairTy(Inst, Def));
}
static MemDepResult getClobber(Instruction *Inst) {
assert(Inst && "Clobber requires inst");
return MemDepResult(PairTy(Inst, Clobber));
}
static MemDepResult getNonLocal() {
return MemDepResult(
PairTy(reinterpret_cast<Instruction*>(NonLocal), Other));
}
static MemDepResult getNonFuncLocal() {
return MemDepResult(
PairTy(reinterpret_cast<Instruction*>(NonFuncLocal), Other));
}
static MemDepResult getUnknown() {
return MemDepResult(
PairTy(reinterpret_cast<Instruction*>(Unknown), Other));
}
/// isClobber - Return true if this MemDepResult represents a query that is
/// an instruction clobber dependency.
bool isClobber() const { return Value.getInt() == Clobber; }
/// isDef - Return true if this MemDepResult represents a query that is
/// an 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() == Other
&& Value.getPointer() == reinterpret_cast<Instruction*>(NonLocal);
}
/// isNonFuncLocal - Return true if this MemDepResult represents a query
/// that is transparent to the start of the function.
bool isNonFuncLocal() const {
return Value.getInt() == Other
&& Value.getPointer() == reinterpret_cast<Instruction*>(NonFuncLocal);
}
/// isUnknown - Return true if this MemDepResult represents a query which
/// cannot and/or will not be computed.
bool isUnknown() const {
return Value.getInt() == Other
&& Value.getPointer() == reinterpret_cast<Instruction*>(Unknown);
}
/// getInst() - If this is a normal dependency, return the instruction that
/// is depended on. Otherwise, return null.
Instruction *getInst() const {
if (Value.getInt() == Other) return NULL;
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));
}
};
/// NonLocalDepEntry - This is an entry in the NonLocalDepInfo cache. For
/// each BasicBlock (the BB entry) it keeps a MemDepResult.
class NonLocalDepEntry {
BasicBlock *BB;
MemDepResult Result;
public:
NonLocalDepEntry(BasicBlock *bb, MemDepResult result)
: BB(bb), Result(result) {}
// This is used for searches.
NonLocalDepEntry(BasicBlock *bb) : BB(bb) {}
// BB is the sort key, it can't be changed.
BasicBlock *getBB() const { return BB; }
void setResult(const MemDepResult &R) { Result = R; }
const MemDepResult &getResult() const { return Result; }
bool operator<(const NonLocalDepEntry &RHS) const {
return BB < RHS.BB;
}
};
/// NonLocalDepResult - This is a result from a NonLocal dependence query.
/// For each BasicBlock (the BB entry) it keeps a MemDepResult and the
/// (potentially phi translated) address that was live in the block.
class NonLocalDepResult {
NonLocalDepEntry Entry;
Value *Address;
public:
NonLocalDepResult(BasicBlock *bb, MemDepResult result, Value *address)
: Entry(bb, result), Address(address) {}
// BB is the sort key, it can't be changed.
BasicBlock *getBB() const { return Entry.getBB(); }
void setResult(const MemDepResult &R, Value *Addr) {
Entry.setResult(R);
Address = Addr;
}
const MemDepResult &getResult() const { return Entry.getResult(); }
/// getAddress - Return the address of this pointer in this block. This can
/// be different than the address queried for the non-local result because
/// of phi translation. This returns null if the address was not available
/// in a block (i.e. because phi translation failed) or if this is a cached
/// result and that address was deleted.
///
/// The address is always null for a non-local 'call' dependence.
Value *getAddress() const { return Address; }
};
/// 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::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<const 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;
/// NonLocalPointerInfo - This record is the information kept for each
/// (value, is load) pair.
struct NonLocalPointerInfo {
/// Pair - The pair of the block and the skip-first-block flag.
BBSkipFirstBlockPair Pair;
/// NonLocalDeps - The results of the query for each relevant block.
NonLocalDepInfo NonLocalDeps;
/// Size - The maximum size of the dereferences of the
/// pointer. May be UnknownSize if the sizes are unknown.
uint64_t Size;
/// TBAATag - The TBAA tag associated with dereferences of the
/// pointer. May be null if there are no tags or conflicting tags.
const MDNode *TBAATag;
NonLocalPointerInfo() : Size(AliasAnalysis::UnknownSize), TBAATag(0) {}
};
/// 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,
NonLocalPointerInfo> 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 from dependencies to the non-local dependees.
ReverseDepMapType ReverseNonLocalDeps;
/// Current AA implementation, just a cache.
AliasAnalysis *AA;
DataLayout *TD;
DominatorTree *DT;
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(const AliasAnalysis::Location &Loc,
bool isLoad, BasicBlock *BB,
SmallVectorImpl<NonLocalDepResult> &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);
/// invalidateCachedPredecessors - Clear the PredIteratorCache info.
/// This needs to be done when the CFG changes, e.g., due to splitting
/// critical edges.
void invalidateCachedPredecessors();
/// getPointerDependencyFrom - Return the instruction on which a memory
/// location depends. If isLoad is true, this routine ignores may-aliases
/// with read-only operations. If isLoad is false, this routine ignores
/// may-aliases with reads from read-only locations. If possible, pass
/// the query instruction as well; this function may take advantage of
/// the metadata annotated to the query instruction to refine the result.
///
/// Note that this is an uncached query, and thus may be inefficient.
///
MemDepResult getPointerDependencyFrom(const AliasAnalysis::Location &Loc,
bool isLoad,
BasicBlock::iterator ScanIt,
BasicBlock *BB,
Instruction *QueryInst = 0);
/// getLoadLoadClobberFullWidthSize - This is a little bit of analysis that
/// looks at a memory location for a load (specified by MemLocBase, Offs,
/// and Size) and compares it against a load. If the specified load could
/// be safely widened to a larger integer load that is 1) still efficient,
/// 2) safe for the target, and 3) would provide the specified memory
/// location value, then this function returns the size in bytes of the
/// load width to use. If not, this returns zero.
static unsigned getLoadLoadClobberFullWidthSize(const Value *MemLocBase,
int64_t MemLocOffs,
unsigned MemLocSize,
const LoadInst *LI,
const DataLayout &TD);
private:
MemDepResult getCallSiteDependencyFrom(CallSite C, bool isReadOnlyCall,
BasicBlock::iterator ScanIt,
BasicBlock *BB);
bool getNonLocalPointerDepFromBB(const PHITransAddr &Pointer,
const AliasAnalysis::Location &Loc,
bool isLoad, BasicBlock *BB,
SmallVectorImpl<NonLocalDepResult> &Result,
DenseMap<BasicBlock*, Value*> &Visited,
bool SkipFirstBlock = false);
MemDepResult GetNonLocalInfoForBlock(const AliasAnalysis::Location &Loc,
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