llvm-6502/include/llvm/Analysis/LoopAccessAnalysis.h
Adam Nemet 4db669fb26 [LoopAccesses] Split out LoopAccessReport from VectorizerReport
The only difference between these two is that VectorizerReport adds a
vectorizer-specific prefix to its messages.  When LAA is used in the
vectorizer context the prefix is added when we promote the
LoopAccessReport into a VectorizerReport via one of the constructors.

This is part of the patchset that converts LoopAccessAnalysis into an
actual analysis pass.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@229897 91177308-0d34-0410-b5e6-96231b3b80d8
2015-02-19 19:15:15 +00:00

275 lines
9.8 KiB
C++

//===- llvm/Analysis/LoopAccessAnalysis.h -----------------------*- 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 interface for the loop memory dependence framework that
// was originally developed for the Loop Vectorizer.
//
//===----------------------------------------------------------------------===//
#ifndef LLVM_ANALYSIS_LOOPACCESSANALYSIS_H
#define LLVM_ANALYSIS_LOOPACCESSANALYSIS_H
#include "llvm/ADT/EquivalenceClasses.h"
#include "llvm/ADT/Optional.h"
#include "llvm/ADT/SetVector.h"
#include "llvm/Analysis/AliasAnalysis.h"
#include "llvm/Analysis/AliasSetTracker.h"
#include "llvm/Analysis/ScalarEvolutionExpressions.h"
#include "llvm/IR/ValueHandle.h"
#include "llvm/Pass.h"
#include "llvm/Support/raw_ostream.h"
namespace llvm {
class Value;
class DataLayout;
class AliasAnalysis;
class ScalarEvolution;
class Loop;
class SCEV;
/// Optimization analysis message produced during vectorization. Messages inform
/// the user why vectorization did not occur.
class LoopAccessReport {
std::string Message;
const Instruction *Instr;
protected:
LoopAccessReport(const Twine &Message, const Instruction *I)
: Message(Message.str()), Instr(I) {}
public:
LoopAccessReport(const Instruction *I = nullptr) : Instr(I) {}
template <typename A> LoopAccessReport &operator<<(const A &Value) {
raw_string_ostream Out(Message);
Out << Value;
return *this;
}
const Instruction *getInstr() const { return Instr; }
std::string &str() { return Message; }
const std::string &str() const { return Message; }
operator Twine() { return Message; }
/// \brief Emit an analysis note for \p PassName with the debug location from
/// the instruction in \p Message if available. Otherwise use the location of
/// \p TheLoop.
static void emitAnalysis(const LoopAccessReport &Message,
const Function *TheFunction,
const Loop *TheLoop,
const char *PassName);
};
/// \brief Collection of parameters shared beetween the Loop Vectorizer and the
/// Loop Access Analysis.
struct VectorizerParams {
/// \brief Maximum SIMD width.
static const unsigned MaxVectorWidth;
/// \brief VF as overridden by the user.
static unsigned VectorizationFactor;
/// \brief Interleave factor as overridden by the user.
static unsigned VectorizationInterleave;
/// \brief True if force-vector-interleave was specified by the user.
static bool isInterleaveForced();
/// \\brief When performing memory disambiguation checks at runtime do not
/// make more than this number of comparisons.
static const unsigned RuntimeMemoryCheckThreshold;
};
/// \brief Drive the analysis of memory accesses in the loop
///
/// This class is responsible for analyzing the memory accesses of a loop. It
/// collects the accesses and then its main helper the AccessAnalysis class
/// finds and categorizes the dependences in buildDependenceSets.
///
/// For memory dependences that can be analyzed at compile time, it determines
/// whether the dependence is part of cycle inhibiting vectorization. This work
/// is delegated to the MemoryDepChecker class.
///
/// For memory dependences that cannot be determined at compile time, it
/// generates run-time checks to prove independence. This is done by
/// AccessAnalysis::canCheckPtrAtRT and the checks are maintained by the
/// RuntimePointerCheck class.
class LoopAccessInfo {
public:
/// This struct holds information about the memory runtime legality check that
/// a group of pointers do not overlap.
struct RuntimePointerCheck {
RuntimePointerCheck() : Need(false) {}
/// Reset the state of the pointer runtime information.
void reset() {
Need = false;
Pointers.clear();
Starts.clear();
Ends.clear();
IsWritePtr.clear();
DependencySetId.clear();
AliasSetId.clear();
}
/// Insert a pointer and calculate the start and end SCEVs.
void insert(ScalarEvolution *SE, Loop *Lp, Value *Ptr, bool WritePtr,
unsigned DepSetId, unsigned ASId, ValueToValueMap &Strides);
/// \brief Decide whether we need to issue a run-time check for pointer at
/// index \p I and \p J to prove their independence.
bool needsChecking(unsigned I, unsigned J) const;
/// This flag indicates if we need to add the runtime check.
bool Need;
/// Holds the pointers that we need to check.
SmallVector<TrackingVH<Value>, 2> Pointers;
/// Holds the pointer value at the beginning of the loop.
SmallVector<const SCEV*, 2> Starts;
/// Holds the pointer value at the end of the loop.
SmallVector<const SCEV*, 2> Ends;
/// Holds the information if this pointer is used for writing to memory.
SmallVector<bool, 2> IsWritePtr;
/// Holds the id of the set of pointers that could be dependent because of a
/// shared underlying object.
SmallVector<unsigned, 2> DependencySetId;
/// Holds the id of the disjoint alias set to which this pointer belongs.
SmallVector<unsigned, 2> AliasSetId;
};
LoopAccessInfo(Loop *L, ScalarEvolution *SE, const DataLayout *DL,
const TargetLibraryInfo *TLI, AliasAnalysis *AA,
DominatorTree *DT, ValueToValueMap &Strides);
/// Return true we can analyze the memory accesses in the loop and there are
/// no memory dependence cycles.
bool canVectorizeMemory() { return CanVecMem; }
RuntimePointerCheck *getRuntimePointerCheck() { return &PtrRtCheck; }
/// Return true if the block BB needs to be predicated in order for the loop
/// to be vectorized.
static bool blockNeedsPredication(BasicBlock *BB, Loop *TheLoop,
DominatorTree *DT);
/// Returns true if the value V is uniform within the loop.
bool isUniform(Value *V);
unsigned getMaxSafeDepDistBytes() const { return MaxSafeDepDistBytes; }
unsigned getNumStores() const { return NumStores; }
unsigned getNumLoads() const { return NumLoads;}
/// \brief Add code that checks at runtime if the accessed arrays overlap.
///
/// Returns a pair of instructions where the first element is the first
/// instruction generated in possibly a sequence of instructions and the
/// second value is the final comparator value or NULL if no check is needed.
std::pair<Instruction *, Instruction *> addRuntimeCheck(Instruction *Loc);
/// \brief The diagnostics report generated for the analysis. E.g. why we
/// couldn't analyze the loop.
Optional<LoopAccessReport> &getReport() { return Report; }
/// \brief Used to ensure that if the analysis was run with speculating the
/// value of symbolic strides, the client queries it with the same assumption.
/// Only used in DEBUG build but we don't want NDEBUG-depedent ABI.
unsigned NumSymbolicStrides;
private:
/// \brief Analyze the loop. Substitute symbolic strides using Strides.
void analyzeLoop(ValueToValueMap &Strides);
/// \brief Check if the structure of the loop allows it to be analyzed by this
/// pass.
bool canAnalyzeLoop();
void emitAnalysis(LoopAccessReport &Message);
/// We need to check that all of the pointers in this list are disjoint
/// at runtime.
RuntimePointerCheck PtrRtCheck;
Loop *TheLoop;
ScalarEvolution *SE;
const DataLayout *DL;
const TargetLibraryInfo *TLI;
AliasAnalysis *AA;
DominatorTree *DT;
unsigned NumLoads;
unsigned NumStores;
unsigned MaxSafeDepDistBytes;
/// \brief Cache the result of analyzeLoop.
bool CanVecMem;
/// \brief The diagnostics report generated for the analysis. E.g. why we
/// couldn't analyze the loop.
Optional<LoopAccessReport> Report;
};
Value *stripIntegerCast(Value *V);
///\brief Return the SCEV corresponding to a pointer with the symbolic stride
///replaced with constant one.
///
/// If \p OrigPtr is not null, use it to look up the stride value instead of \p
/// Ptr. \p PtrToStride provides the mapping between the pointer value and its
/// stride as collected by LoopVectorizationLegality::collectStridedAccess.
const SCEV *replaceSymbolicStrideSCEV(ScalarEvolution *SE,
ValueToValueMap &PtrToStride,
Value *Ptr, Value *OrigPtr = nullptr);
/// \brief This analysis provides dependence information for the memory accesses
/// of a loop.
///
/// It runs the analysis for a loop on demand. This can be initiated by
/// querying the loop access info via LAA::getInfo. getInfo return a
/// LoopAccessInfo object. See this class for the specifics of what information
/// is provided.
class LoopAccessAnalysis : public FunctionPass {
public:
static char ID;
LoopAccessAnalysis() : FunctionPass(ID) {
initializeLoopAccessAnalysisPass(*PassRegistry::getPassRegistry());
}
bool runOnFunction(Function &F) override;
void getAnalysisUsage(AnalysisUsage &AU) const override;
/// \brief Query the result of the loop access information for the loop \p L.
///
/// If the client speculates (and then issues run-time checks) for the values
/// of symbolic strides, \p Strides provides the mapping (see
/// replaceSymbolicStrideSCEV). If there is no cached result available run
/// the analysis.
LoopAccessInfo &getInfo(Loop *L, ValueToValueMap &Strides);
void releaseMemory() override {
// Invalidate the cache when the pass is freed.
LoopAccessInfoMap.clear();
}
private:
/// \brief The cache.
DenseMap<Loop *, std::unique_ptr<LoopAccessInfo>> LoopAccessInfoMap;
// The used analysis passes.
ScalarEvolution *SE;
const DataLayout *DL;
const TargetLibraryInfo *TLI;
AliasAnalysis *AA;
DominatorTree *DT;
};
} // End llvm namespace
#endif