| //===- llvm/Analysis/ScalarEvolution.h - Scalar Evolution -------*- C++ -*-===// |
| // |
| // The LLVM Compiler Infrastructure |
| // |
| // This file is distributed under the University of Illinois Open Source |
| // License. See LICENSE.TXT for details. |
| // |
| //===----------------------------------------------------------------------===// |
| // |
| // The ScalarEvolution class is an LLVM pass which can be used to analyze and |
| // catagorize scalar expressions in loops. It specializes in recognizing |
| // general induction variables, representing them with the abstract and opaque |
| // SCEV class. Given this analysis, trip counts of loops and other important |
| // properties can be obtained. |
| // |
| // This analysis is primarily useful for induction variable substitution and |
| // strength reduction. |
| // |
| //===----------------------------------------------------------------------===// |
| |
| #ifndef LLVM_ANALYSIS_SCALAREVOLUTION_H |
| #define LLVM_ANALYSIS_SCALAREVOLUTION_H |
| |
| #include "llvm/Pass.h" |
| #include "llvm/Analysis/LoopInfo.h" |
| #include "llvm/Support/DataTypes.h" |
| #include "llvm/Support/ValueHandle.h" |
| #include <iosfwd> |
| |
| namespace llvm { |
| class APInt; |
| class ConstantInt; |
| class Type; |
| class SCEVHandle; |
| class ScalarEvolution; |
| class TargetData; |
| |
| /// SCEV - This class represent an analyzed expression in the program. These |
| /// are reference counted opaque objects that the client is not allowed to |
| /// do much with directly. |
| /// |
| class SCEV { |
| const unsigned SCEVType; // The SCEV baseclass this node corresponds to |
| mutable unsigned RefCount; |
| |
| friend class SCEVHandle; |
| void addRef() const { ++RefCount; } |
| void dropRef() const { |
| if (--RefCount == 0) |
| delete this; |
| } |
| |
| SCEV(const SCEV &); // DO NOT IMPLEMENT |
| void operator=(const SCEV &); // DO NOT IMPLEMENT |
| protected: |
| virtual ~SCEV(); |
| public: |
| explicit SCEV(unsigned SCEVTy) : SCEVType(SCEVTy), RefCount(0) {} |
| |
| unsigned getSCEVType() const { return SCEVType; } |
| |
| /// isLoopInvariant - Return true if the value of this SCEV is unchanging in |
| /// the specified loop. |
| virtual bool isLoopInvariant(const Loop *L) const = 0; |
| |
| /// hasComputableLoopEvolution - Return true if this SCEV changes value in a |
| /// known way in the specified loop. This property being true implies that |
| /// the value is variant in the loop AND that we can emit an expression to |
| /// compute the value of the expression at any particular loop iteration. |
| virtual bool hasComputableLoopEvolution(const Loop *L) const = 0; |
| |
| /// getType - Return the LLVM type of this SCEV expression. |
| /// |
| virtual const Type *getType() const = 0; |
| |
| /// isZero - Return true if the expression is a constant zero. |
| /// |
| bool isZero() const; |
| |
| /// isOne - Return true if the expression is a constant one. |
| /// |
| bool isOne() const; |
| |
| /// replaceSymbolicValuesWithConcrete - If this SCEV internally references |
| /// the symbolic value "Sym", construct and return a new SCEV that produces |
| /// the same value, but which uses the concrete value Conc instead of the |
| /// symbolic value. If this SCEV does not use the symbolic value, it |
| /// returns itself. |
| virtual SCEVHandle |
| replaceSymbolicValuesWithConcrete(const SCEVHandle &Sym, |
| const SCEVHandle &Conc, |
| ScalarEvolution &SE) const = 0; |
| |
| /// dominates - Return true if elements that makes up this SCEV dominates |
| /// the specified basic block. |
| virtual bool dominates(BasicBlock *BB, DominatorTree *DT) const = 0; |
| |
| /// print - Print out the internal representation of this scalar to the |
| /// specified stream. This should really only be used for debugging |
| /// purposes. |
| virtual void print(raw_ostream &OS) const = 0; |
| void print(std::ostream &OS) const; |
| void print(std::ostream *OS) const { if (OS) print(*OS); } |
| |
| /// dump - This method is used for debugging. |
| /// |
| void dump() const; |
| }; |
| |
| inline raw_ostream &operator<<(raw_ostream &OS, const SCEV &S) { |
| S.print(OS); |
| return OS; |
| } |
| |
| inline std::ostream &operator<<(std::ostream &OS, const SCEV &S) { |
| S.print(OS); |
| return OS; |
| } |
| |
| /// SCEVCouldNotCompute - An object of this class is returned by queries that |
| /// could not be answered. For example, if you ask for the number of |
| /// iterations of a linked-list traversal loop, you will get one of these. |
| /// None of the standard SCEV operations are valid on this class, it is just a |
| /// marker. |
| struct SCEVCouldNotCompute : public SCEV { |
| SCEVCouldNotCompute(); |
| ~SCEVCouldNotCompute(); |
| |
| // None of these methods are valid for this object. |
| virtual bool isLoopInvariant(const Loop *L) const; |
| virtual const Type *getType() const; |
| virtual bool hasComputableLoopEvolution(const Loop *L) const; |
| virtual void print(raw_ostream &OS) const; |
| virtual SCEVHandle |
| replaceSymbolicValuesWithConcrete(const SCEVHandle &Sym, |
| const SCEVHandle &Conc, |
| ScalarEvolution &SE) const; |
| |
| virtual bool dominates(BasicBlock *BB, DominatorTree *DT) const { |
| return true; |
| } |
| |
| /// Methods for support type inquiry through isa, cast, and dyn_cast: |
| static inline bool classof(const SCEVCouldNotCompute *S) { return true; } |
| static bool classof(const SCEV *S); |
| }; |
| |
| /// SCEVHandle - This class is used to maintain the SCEV object's refcounts, |
| /// freeing the objects when the last reference is dropped. |
| class SCEVHandle { |
| const SCEV *S; |
| SCEVHandle(); // DO NOT IMPLEMENT |
| public: |
| SCEVHandle(const SCEV *s) : S(s) { |
| assert(S && "Cannot create a handle to a null SCEV!"); |
| S->addRef(); |
| } |
| SCEVHandle(const SCEVHandle &RHS) : S(RHS.S) { |
| S->addRef(); |
| } |
| ~SCEVHandle() { S->dropRef(); } |
| |
| operator const SCEV*() const { return S; } |
| |
| const SCEV &operator*() const { return *S; } |
| const SCEV *operator->() const { return S; } |
| |
| bool operator==(const SCEV *RHS) const { return S == RHS; } |
| bool operator!=(const SCEV *RHS) const { return S != RHS; } |
| |
| const SCEVHandle &operator=(SCEV *RHS) { |
| if (S != RHS) { |
| S->dropRef(); |
| S = RHS; |
| S->addRef(); |
| } |
| return *this; |
| } |
| |
| const SCEVHandle &operator=(const SCEVHandle &RHS) { |
| if (S != RHS.S) { |
| S->dropRef(); |
| S = RHS.S; |
| S->addRef(); |
| } |
| return *this; |
| } |
| }; |
| |
| template<typename From> struct simplify_type; |
| template<> struct simplify_type<const SCEVHandle> { |
| typedef const SCEV* SimpleType; |
| static SimpleType getSimplifiedValue(const SCEVHandle &Node) { |
| return Node; |
| } |
| }; |
| template<> struct simplify_type<SCEVHandle> |
| : public simplify_type<const SCEVHandle> {}; |
| |
| /// ScalarEvolution - This class is the main scalar evolution driver. Because |
| /// client code (intentionally) can't do much with the SCEV objects directly, |
| /// they must ask this class for services. |
| /// |
| class ScalarEvolution : public FunctionPass { |
| /// SCEVCallbackVH - A CallbackVH to arrange for ScalarEvolution to be |
| /// notified whenever a Value is deleted. |
| class SCEVCallbackVH : public CallbackVH { |
| ScalarEvolution *SE; |
| virtual void deleted(); |
| virtual void allUsesReplacedWith(Value *New); |
| public: |
| SCEVCallbackVH(Value *V, ScalarEvolution *SE = 0); |
| }; |
| |
| friend class SCEVCallbackVH; |
| friend class SCEVExpander; |
| |
| /// F - The function we are analyzing. |
| /// |
| Function *F; |
| |
| /// LI - The loop information for the function we are currently analyzing. |
| /// |
| LoopInfo *LI; |
| |
| /// TD - The target data information for the target we are targetting. |
| /// |
| TargetData *TD; |
| |
| /// UnknownValue - This SCEV is used to represent unknown trip counts and |
| /// things. |
| SCEVHandle UnknownValue; |
| |
| /// Scalars - This is a cache of the scalars we have analyzed so far. |
| /// |
| std::map<SCEVCallbackVH, SCEVHandle> Scalars; |
| |
| /// BackedgeTakenInfo - Information about the backedge-taken count |
| /// of a loop. This currently inclues an exact count and a maximum count. |
| /// |
| struct BackedgeTakenInfo { |
| /// Exact - An expression indicating the exact backedge-taken count of |
| /// the loop if it is known, or a SCEVCouldNotCompute otherwise. |
| SCEVHandle Exact; |
| |
| /// Exact - An expression indicating the least maximum backedge-taken |
| /// count of the loop that is known, or a SCEVCouldNotCompute. |
| SCEVHandle Max; |
| |
| /*implicit*/ BackedgeTakenInfo(SCEVHandle exact) : |
| Exact(exact), Max(exact) {} |
| |
| /*implicit*/ BackedgeTakenInfo(const SCEV *exact) : |
| Exact(exact), Max(exact) {} |
| |
| BackedgeTakenInfo(SCEVHandle exact, SCEVHandle max) : |
| Exact(exact), Max(max) {} |
| |
| /// hasAnyInfo - Test whether this BackedgeTakenInfo contains any |
| /// computed information, or whether it's all SCEVCouldNotCompute |
| /// values. |
| bool hasAnyInfo() const { |
| return !isa<SCEVCouldNotCompute>(Exact) || |
| !isa<SCEVCouldNotCompute>(Max); |
| } |
| }; |
| |
| /// BackedgeTakenCounts - Cache the backedge-taken count of the loops for |
| /// this function as they are computed. |
| std::map<const Loop*, BackedgeTakenInfo> BackedgeTakenCounts; |
| |
| /// ConstantEvolutionLoopExitValue - This map contains entries for all of |
| /// the PHI instructions that we attempt to compute constant evolutions for. |
| /// This allows us to avoid potentially expensive recomputation of these |
| /// properties. An instruction maps to null if we are unable to compute its |
| /// exit value. |
| std::map<PHINode*, Constant*> ConstantEvolutionLoopExitValue; |
| |
| /// ValuesAtScopes - This map contains entries for all the instructions |
| /// that we attempt to compute getSCEVAtScope information for without |
| /// using SCEV techniques, which can be expensive. |
| std::map<Instruction *, std::map<const Loop *, Constant *> > ValuesAtScopes; |
| |
| /// createSCEV - We know that there is no SCEV for the specified value. |
| /// Analyze the expression. |
| SCEVHandle createSCEV(Value *V); |
| |
| /// createNodeForPHI - Provide the special handling we need to analyze PHI |
| /// SCEVs. |
| SCEVHandle createNodeForPHI(PHINode *PN); |
| |
| /// createNodeForGEP - Provide the special handling we need to analyze GEP |
| /// SCEVs. |
| SCEVHandle createNodeForGEP(User *GEP); |
| |
| /// ReplaceSymbolicValueWithConcrete - This looks up the computed SCEV value |
| /// for the specified instruction and replaces any references to the |
| /// symbolic value SymName with the specified value. This is used during |
| /// PHI resolution. |
| void ReplaceSymbolicValueWithConcrete(Instruction *I, |
| const SCEVHandle &SymName, |
| const SCEVHandle &NewVal); |
| |
| /// getBackedgeTakenInfo - Return the BackedgeTakenInfo for the given |
| /// loop, lazily computing new values if the loop hasn't been analyzed |
| /// yet. |
| const BackedgeTakenInfo &getBackedgeTakenInfo(const Loop *L); |
| |
| /// ComputeBackedgeTakenCount - Compute the number of times the specified |
| /// loop will iterate. |
| BackedgeTakenInfo ComputeBackedgeTakenCount(const Loop *L); |
| |
| /// ComputeLoadConstantCompareBackedgeTakenCount - Given an exit condition |
| /// of 'icmp op load X, cst', try to see if we can compute the trip count. |
| SCEVHandle |
| ComputeLoadConstantCompareBackedgeTakenCount(LoadInst *LI, |
| Constant *RHS, |
| const Loop *L, |
| ICmpInst::Predicate p); |
| |
| /// ComputeBackedgeTakenCountExhaustively - If the trip is known to execute |
| /// a constant number of times (the condition evolves only from constants), |
| /// try to evaluate a few iterations of the loop until we get the exit |
| /// condition gets a value of ExitWhen (true or false). If we cannot |
| /// evaluate the trip count of the loop, return UnknownValue. |
| SCEVHandle ComputeBackedgeTakenCountExhaustively(const Loop *L, Value *Cond, |
| bool ExitWhen); |
| |
| /// HowFarToZero - Return the number of times a backedge comparing the |
| /// specified value to zero will execute. If not computable, return |
| /// UnknownValue. |
| SCEVHandle HowFarToZero(const SCEV *V, const Loop *L); |
| |
| /// HowFarToNonZero - Return the number of times a backedge checking the |
| /// specified value for nonzero will execute. If not computable, return |
| /// UnknownValue. |
| SCEVHandle HowFarToNonZero(const SCEV *V, const Loop *L); |
| |
| /// HowManyLessThans - Return the number of times a backedge containing the |
| /// specified less-than comparison will execute. If not computable, return |
| /// UnknownValue. isSigned specifies whether the less-than is signed. |
| BackedgeTakenInfo HowManyLessThans(const SCEV *LHS, const SCEV *RHS, |
| const Loop *L, bool isSigned); |
| |
| /// getLoopPredecessor - If the given loop's header has exactly one unique |
| /// predecessor outside the loop, return it. Otherwise return null. |
| BasicBlock *getLoopPredecessor(const Loop *L); |
| |
| /// getPredecessorWithUniqueSuccessorForBB - Return a predecessor of BB |
| /// (which may not be an immediate predecessor) which has exactly one |
| /// successor from which BB is reachable, or null if no such block is |
| /// found. |
| BasicBlock* getPredecessorWithUniqueSuccessorForBB(BasicBlock *BB); |
| |
| /// getConstantEvolutionLoopExitValue - If we know that the specified Phi is |
| /// in the header of its containing loop, we know the loop executes a |
| /// constant number of times, and the PHI node is just a recurrence |
| /// involving constants, fold it. |
| Constant *getConstantEvolutionLoopExitValue(PHINode *PN, const APInt& BEs, |
| const Loop *L); |
| |
| /// forgetLoopPHIs - Delete the memoized SCEVs associated with the |
| /// PHI nodes in the given loop. This is used when the trip count of |
| /// the loop may have changed. |
| void forgetLoopPHIs(const Loop *L); |
| |
| public: |
| static char ID; // Pass identification, replacement for typeid |
| ScalarEvolution(); |
| |
| /// isSCEVable - Test if values of the given type are analyzable within |
| /// the SCEV framework. This primarily includes integer types, and it |
| /// can optionally include pointer types if the ScalarEvolution class |
| /// has access to target-specific information. |
| bool isSCEVable(const Type *Ty) const; |
| |
| /// getTypeSizeInBits - Return the size in bits of the specified type, |
| /// for which isSCEVable must return true. |
| uint64_t getTypeSizeInBits(const Type *Ty) const; |
| |
| /// getEffectiveSCEVType - Return a type with the same bitwidth as |
| /// the given type and which represents how SCEV will treat the given |
| /// type, for which isSCEVable must return true. For pointer types, |
| /// this is the pointer-sized integer type. |
| const Type *getEffectiveSCEVType(const Type *Ty) const; |
| |
| /// getSCEV - Return a SCEV expression handle for the full generality of the |
| /// specified expression. |
| SCEVHandle getSCEV(Value *V); |
| |
| SCEVHandle getConstant(ConstantInt *V); |
| SCEVHandle getConstant(const APInt& Val); |
| SCEVHandle getTruncateExpr(const SCEVHandle &Op, const Type *Ty); |
| SCEVHandle getZeroExtendExpr(const SCEVHandle &Op, const Type *Ty); |
| SCEVHandle getSignExtendExpr(const SCEVHandle &Op, const Type *Ty); |
| SCEVHandle getAddExpr(std::vector<SCEVHandle> &Ops); |
| SCEVHandle getAddExpr(const SCEVHandle &LHS, const SCEVHandle &RHS) { |
| std::vector<SCEVHandle> Ops; |
| Ops.push_back(LHS); |
| Ops.push_back(RHS); |
| return getAddExpr(Ops); |
| } |
| SCEVHandle getAddExpr(const SCEVHandle &Op0, const SCEVHandle &Op1, |
| const SCEVHandle &Op2) { |
| std::vector<SCEVHandle> Ops; |
| Ops.push_back(Op0); |
| Ops.push_back(Op1); |
| Ops.push_back(Op2); |
| return getAddExpr(Ops); |
| } |
| SCEVHandle getMulExpr(std::vector<SCEVHandle> &Ops); |
| SCEVHandle getMulExpr(const SCEVHandle &LHS, const SCEVHandle &RHS) { |
| std::vector<SCEVHandle> Ops; |
| Ops.push_back(LHS); |
| Ops.push_back(RHS); |
| return getMulExpr(Ops); |
| } |
| SCEVHandle getUDivExpr(const SCEVHandle &LHS, const SCEVHandle &RHS); |
| SCEVHandle getAddRecExpr(const SCEVHandle &Start, const SCEVHandle &Step, |
| const Loop *L); |
| SCEVHandle getAddRecExpr(std::vector<SCEVHandle> &Operands, |
| const Loop *L); |
| SCEVHandle getAddRecExpr(const std::vector<SCEVHandle> &Operands, |
| const Loop *L) { |
| std::vector<SCEVHandle> NewOp(Operands); |
| return getAddRecExpr(NewOp, L); |
| } |
| SCEVHandle getSMaxExpr(const SCEVHandle &LHS, const SCEVHandle &RHS); |
| SCEVHandle getSMaxExpr(std::vector<SCEVHandle> Operands); |
| SCEVHandle getUMaxExpr(const SCEVHandle &LHS, const SCEVHandle &RHS); |
| SCEVHandle getUMaxExpr(std::vector<SCEVHandle> Operands); |
| SCEVHandle getUnknown(Value *V); |
| SCEVHandle getCouldNotCompute(); |
| |
| /// getNegativeSCEV - Return the SCEV object corresponding to -V. |
| /// |
| SCEVHandle getNegativeSCEV(const SCEVHandle &V); |
| |
| /// getNotSCEV - Return the SCEV object corresponding to ~V. |
| /// |
| SCEVHandle getNotSCEV(const SCEVHandle &V); |
| |
| /// getMinusSCEV - Return LHS-RHS. |
| /// |
| SCEVHandle getMinusSCEV(const SCEVHandle &LHS, |
| const SCEVHandle &RHS); |
| |
| /// getTruncateOrZeroExtend - Return a SCEV corresponding to a conversion |
| /// of the input value to the specified type. If the type must be |
| /// extended, it is zero extended. |
| SCEVHandle getTruncateOrZeroExtend(const SCEVHandle &V, const Type *Ty); |
| |
| /// getTruncateOrSignExtend - Return a SCEV corresponding to a conversion |
| /// of the input value to the specified type. If the type must be |
| /// extended, it is sign extended. |
| SCEVHandle getTruncateOrSignExtend(const SCEVHandle &V, const Type *Ty); |
| |
| /// getNoopOrZeroExtend - Return a SCEV corresponding to a conversion of |
| /// the input value to the specified type. If the type must be extended, |
| /// it is zero extended. The conversion must not be narrowing. |
| SCEVHandle getNoopOrZeroExtend(const SCEVHandle &V, const Type *Ty); |
| |
| /// getNoopOrSignExtend - Return a SCEV corresponding to a conversion of |
| /// the input value to the specified type. If the type must be extended, |
| /// it is sign extended. The conversion must not be narrowing. |
| SCEVHandle getNoopOrSignExtend(const SCEVHandle &V, const Type *Ty); |
| |
| /// getTruncateOrNoop - Return a SCEV corresponding to a conversion of the |
| /// input value to the specified type. The conversion must not be |
| /// widening. |
| SCEVHandle getTruncateOrNoop(const SCEVHandle &V, const Type *Ty); |
| |
| /// getIntegerSCEV - Given an integer or FP type, create a constant for the |
| /// specified signed integer value and return a SCEV for the constant. |
| SCEVHandle getIntegerSCEV(int Val, const Type *Ty); |
| |
| /// hasSCEV - Return true if the SCEV for this value has already been |
| /// computed. |
| bool hasSCEV(Value *V) const; |
| |
| /// setSCEV - Insert the specified SCEV into the map of current SCEVs for |
| /// the specified value. |
| void setSCEV(Value *V, const SCEVHandle &H); |
| |
| /// getSCEVAtScope - Return a SCEV expression handle for the specified value |
| /// at the specified scope in the program. The L value specifies a loop |
| /// nest to evaluate the expression at, where null is the top-level or a |
| /// specified loop is immediately inside of the loop. |
| /// |
| /// This method can be used to compute the exit value for a variable defined |
| /// in a loop by querying what the value will hold in the parent loop. |
| /// |
| /// In the case that a relevant loop exit value cannot be computed, the |
| /// original value V is returned. |
| SCEVHandle getSCEVAtScope(const SCEV *S, const Loop *L); |
| |
| /// getSCEVAtScope - This is a convenience function which does |
| /// getSCEVAtScope(getSCEV(V), L). |
| SCEVHandle getSCEVAtScope(Value *V, const Loop *L); |
| |
| /// isLoopGuardedByCond - Test whether entry to the loop is protected by |
| /// a conditional between LHS and RHS. This is used to help avoid max |
| /// expressions in loop trip counts. |
| bool isLoopGuardedByCond(const Loop *L, ICmpInst::Predicate Pred, |
| const SCEV *LHS, const SCEV *RHS); |
| |
| /// getBackedgeTakenCount - If the specified loop has a predictable |
| /// backedge-taken count, return it, otherwise return a SCEVCouldNotCompute |
| /// object. The backedge-taken count is the number of times the loop header |
| /// will be branched to from within the loop. This is one less than the |
| /// trip count of the loop, since it doesn't count the first iteration, |
| /// when the header is branched to from outside the loop. |
| /// |
| /// Note that it is not valid to call this method on a loop without a |
| /// loop-invariant backedge-taken count (see |
| /// hasLoopInvariantBackedgeTakenCount). |
| /// |
| SCEVHandle getBackedgeTakenCount(const Loop *L); |
| |
| /// getMaxBackedgeTakenCount - Similar to getBackedgeTakenCount, except |
| /// return the least SCEV value that is known never to be less than the |
| /// actual backedge taken count. |
| SCEVHandle getMaxBackedgeTakenCount(const Loop *L); |
| |
| /// hasLoopInvariantBackedgeTakenCount - Return true if the specified loop |
| /// has an analyzable loop-invariant backedge-taken count. |
| bool hasLoopInvariantBackedgeTakenCount(const Loop *L); |
| |
| /// forgetLoopBackedgeTakenCount - This method should be called by the |
| /// client when it has changed a loop in a way that may effect |
| /// ScalarEvolution's ability to compute a trip count, or if the loop |
| /// is deleted. |
| void forgetLoopBackedgeTakenCount(const Loop *L); |
| |
| virtual bool runOnFunction(Function &F); |
| virtual void releaseMemory(); |
| virtual void getAnalysisUsage(AnalysisUsage &AU) const; |
| void print(raw_ostream &OS, const Module* = 0) const; |
| virtual void print(std::ostream &OS, const Module* = 0) const; |
| void print(std::ostream *OS, const Module* M = 0) const { |
| if (OS) print(*OS, M); |
| } |
| }; |
| } |
| |
| #endif |