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llvm-mirror/include/llvm/Analysis/ScalarEvolution.h
Andrew Trick 60f6beef61 Expose isNonConstantNegative to users of ScalarEvolution. 
llvm-svn: 147700
2012-01-07 00:27:31 +00:00

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//===- 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
// categorize 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/Instructions.h"
#include "llvm/Function.h"
#include "llvm/Operator.h"
#include "llvm/Support/DataTypes.h"
#include "llvm/Support/ValueHandle.h"
#include "llvm/Support/Allocator.h"
#include "llvm/Support/ConstantRange.h"
#include "llvm/ADT/FoldingSet.h"
#include "llvm/ADT/DenseMap.h"
#include <map>
namespace llvm {
class APInt;
class Constant;
class ConstantInt;
class DominatorTree;
class Type;
class ScalarEvolution;
class TargetData;
class TargetLibraryInfo;
class LLVMContext;
class Loop;
class LoopInfo;
class Operator;
class SCEVUnknown;
class SCEV;
template<> struct FoldingSetTrait<SCEV>;
/// SCEV - This class represents an analyzed expression in the program. These
/// are opaque objects that the client is not allowed to do much with
/// directly.
///
class SCEV : public FoldingSetNode {
friend struct FoldingSetTrait<SCEV>;
/// FastID - A reference to an Interned FoldingSetNodeID for this node.
/// The ScalarEvolution's BumpPtrAllocator holds the data.
FoldingSetNodeIDRef FastID;
// The SCEV baseclass this node corresponds to
const unsigned short SCEVType;
protected:
/// SubclassData - This field is initialized to zero and may be used in
/// subclasses to store miscellaneous information.
unsigned short SubclassData;
private:
SCEV(const SCEV &); // DO NOT IMPLEMENT
void operator=(const SCEV &); // DO NOT IMPLEMENT
public:
/// NoWrapFlags are bitfield indices into SubclassData.
///
/// Add and Mul expressions may have no-unsigned-wrap <NUW> or
/// no-signed-wrap <NSW> properties, which are derived from the IR
/// operator. NSW is a misnomer that we use to mean no signed overflow or
/// underflow.
///
/// AddRec expression may have a no-self-wraparound <NW> property if the
/// result can never reach the start value. This property is independent of
/// the actual start value and step direction. Self-wraparound is defined
/// purely in terms of the recurrence's loop, step size, and
/// bitwidth. Formally, a recurrence with no self-wraparound satisfies:
/// abs(step) * max-iteration(loop) <= unsigned-max(bitwidth).
///
/// Note that NUW and NSW are also valid properties of a recurrence, and
/// either implies NW. For convenience, NW will be set for a recurrence
/// whenever either NUW or NSW are set.
enum NoWrapFlags { FlagAnyWrap = 0, // No guarantee.
FlagNW = (1 << 0), // No self-wrap.
FlagNUW = (1 << 1), // No unsigned wrap.
FlagNSW = (1 << 2), // No signed wrap.
NoWrapMask = (1 << 3) -1 };
explicit SCEV(const FoldingSetNodeIDRef ID, unsigned SCEVTy) :
FastID(ID), SCEVType(SCEVTy), SubclassData(0) {}
unsigned getSCEVType() const { return SCEVType; }
/// getType - Return the LLVM type of this SCEV expression.
///
Type *getType() const;
/// 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;
/// isAllOnesValue - Return true if the expression is a constant
/// all-ones value.
///
bool isAllOnesValue() const;
/// isNonConstantNegative - Return true if the specified scev is negated,
/// but not a constant.
bool isNonConstantNegative() const;
/// print - Print out the internal representation of this scalar to the
/// specified stream. This should really only be used for debugging
/// purposes.
void print(raw_ostream &OS) const;
/// dump - This method is used for debugging.
///
void dump() const;
};
// Specialize FoldingSetTrait for SCEV to avoid needing to compute
// temporary FoldingSetNodeID values.
template<> struct FoldingSetTrait<SCEV> : DefaultFoldingSetTrait<SCEV> {
static void Profile(const SCEV &X, FoldingSetNodeID& ID) {
ID = X.FastID;
}
static bool Equals(const SCEV &X, const FoldingSetNodeID &ID,
FoldingSetNodeID &TempID) {
return ID == X.FastID;
}
static unsigned ComputeHash(const SCEV &X, FoldingSetNodeID &TempID) {
return X.FastID.ComputeHash();
}
};
inline raw_ostream &operator<<(raw_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();
/// 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);
};
/// 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 {
public:
/// LoopDisposition - An enum describing the relationship between a
/// SCEV and a loop.
enum LoopDisposition {
LoopVariant, ///< The SCEV is loop-variant (unknown).
LoopInvariant, ///< The SCEV is loop-invariant.
LoopComputable ///< The SCEV varies predictably with the loop.
};
/// BlockDisposition - An enum describing the relationship between a
/// SCEV and a basic block.
enum BlockDisposition {
DoesNotDominateBlock, ///< The SCEV does not dominate the block.
DominatesBlock, ///< The SCEV dominates the block.
ProperlyDominatesBlock ///< The SCEV properly dominates the block.
};
/// Convenient NoWrapFlags manipulation that hides enum casts and is
/// visible in the ScalarEvolution name space.
static SCEV::NoWrapFlags maskFlags(SCEV::NoWrapFlags Flags, int Mask) {
return (SCEV::NoWrapFlags)(Flags & Mask);
}
static SCEV::NoWrapFlags setFlags(SCEV::NoWrapFlags Flags,
SCEV::NoWrapFlags OnFlags) {
return (SCEV::NoWrapFlags)(Flags | OnFlags);
}
static SCEV::NoWrapFlags clearFlags(SCEV::NoWrapFlags Flags,
SCEV::NoWrapFlags OffFlags) {
return (SCEV::NoWrapFlags)(Flags & ~OffFlags);
}
private:
/// 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;
friend class SCEVUnknown;
/// 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 targeting.
///
TargetData *TD;
/// TLI - The target library information for the target we are targeting.
///
TargetLibraryInfo *TLI;
/// DT - The dominator tree.
///
DominatorTree *DT;
/// CouldNotCompute - This SCEV is used to represent unknown trip
/// counts and things.
SCEVCouldNotCompute CouldNotCompute;
/// ValueExprMapType - The typedef for ValueExprMap.
///
typedef DenseMap<SCEVCallbackVH, const SCEV *, DenseMapInfo<Value *> >
ValueExprMapType;
/// ValueExprMap - This is a cache of the values we have analyzed so far.
///
ValueExprMapType ValueExprMap;
/// ExitLimit - Information about the number of loop iterations for
/// which a loop exit's branch condition evaluates to the not-taken path.
/// This is a temporary pair of exact and max expressions that are
/// eventually summarized in ExitNotTakenInfo and BackedgeTakenInfo.
struct ExitLimit {
const SCEV *Exact;
const SCEV *Max;
/*implicit*/ ExitLimit(const SCEV *E) : Exact(E), Max(E) {}
ExitLimit(const SCEV *E, const SCEV *M) : Exact(E), Max(M) {}
/// hasAnyInfo - Test whether this ExitLimit contains any computed
/// information, or whether it's all SCEVCouldNotCompute values.
bool hasAnyInfo() const {
return !isa<SCEVCouldNotCompute>(Exact) ||
!isa<SCEVCouldNotCompute>(Max);
}
};
/// ExitNotTakenInfo - Information about the number of times a particular
/// loop exit may be reached before exiting the loop.
struct ExitNotTakenInfo {
AssertingVH<BasicBlock> ExitingBlock;
const SCEV *ExactNotTaken;
PointerIntPair<ExitNotTakenInfo*, 1> NextExit;
ExitNotTakenInfo() : ExitingBlock(0), ExactNotTaken(0) {}
/// isCompleteList - Return true if all loop exits are computable.
bool isCompleteList() const {
return NextExit.getInt() == 0;
}
void setIncomplete() { NextExit.setInt(1); }
/// getNextExit - Return a pointer to the next exit's not-taken info.
ExitNotTakenInfo *getNextExit() const {
return NextExit.getPointer();
}
void setNextExit(ExitNotTakenInfo *ENT) { NextExit.setPointer(ENT); }
};
/// BackedgeTakenInfo - Information about the backedge-taken count
/// of a loop. This currently includes an exact count and a maximum count.
///
class BackedgeTakenInfo {
/// ExitNotTaken - A list of computable exits and their not-taken counts.
/// Loops almost never have more than one computable exit.
ExitNotTakenInfo ExitNotTaken;
/// Max - An expression indicating the least maximum backedge-taken
/// count of the loop that is known, or a SCEVCouldNotCompute.
const SCEV *Max;
public:
BackedgeTakenInfo() : Max(0) {}
/// Initialize BackedgeTakenInfo from a list of exact exit counts.
BackedgeTakenInfo(
SmallVectorImpl< std::pair<BasicBlock *, const SCEV *> > &ExitCounts,
bool Complete, const SCEV *MaxCount);
/// hasAnyInfo - Test whether this BackedgeTakenInfo contains any
/// computed information, or whether it's all SCEVCouldNotCompute
/// values.
bool hasAnyInfo() const {
return ExitNotTaken.ExitingBlock || !isa<SCEVCouldNotCompute>(Max);
}
/// getExact - Return an expression indicating the exact backedge-taken
/// count of the loop if it is known, or SCEVCouldNotCompute
/// otherwise. This is the number of times the loop header can be
/// guaranteed to execute, minus one.
const SCEV *getExact(ScalarEvolution *SE) const;
/// getExact - Return the number of times this loop exit may fall through
/// to the back edge, or SCEVCouldNotCompute. The loop is guaranteed not
/// to exit via this block before this number of iterations, but may exit
/// via another block.
const SCEV *getExact(BasicBlock *ExitingBlock, ScalarEvolution *SE) const;
/// getMax - Get the max backedge taken count for the loop.
const SCEV *getMax(ScalarEvolution *SE) const;
/// clear - Invalidate this result and free associated memory.
void clear();
};
/// BackedgeTakenCounts - Cache the backedge-taken count of the loops for
/// this function as they are computed.
DenseMap<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.
DenseMap<PHINode*, Constant*> ConstantEvolutionLoopExitValue;
/// ValuesAtScopes - This map contains entries for all the expressions
/// that we attempt to compute getSCEVAtScope information for, which can
/// be expensive in extreme cases.
DenseMap<const SCEV *,
std::map<const Loop *, const SCEV *> > ValuesAtScopes;
/// LoopDispositions - Memoized computeLoopDisposition results.
DenseMap<const SCEV *,
std::map<const Loop *, LoopDisposition> > LoopDispositions;
/// computeLoopDisposition - Compute a LoopDisposition value.
LoopDisposition computeLoopDisposition(const SCEV *S, const Loop *L);
/// BlockDispositions - Memoized computeBlockDisposition results.
DenseMap<const SCEV *,
std::map<const BasicBlock *, BlockDisposition> > BlockDispositions;
/// computeBlockDisposition - Compute a BlockDisposition value.
BlockDisposition computeBlockDisposition(const SCEV *S, const BasicBlock *BB);
/// UnsignedRanges - Memoized results from getUnsignedRange
DenseMap<const SCEV *, ConstantRange> UnsignedRanges;
/// SignedRanges - Memoized results from getSignedRange
DenseMap<const SCEV *, ConstantRange> SignedRanges;
/// setUnsignedRange - Set the memoized unsigned range for the given SCEV.
const ConstantRange &setUnsignedRange(const SCEV *S,
const ConstantRange &CR) {
std::pair<DenseMap<const SCEV *, ConstantRange>::iterator, bool> Pair =
UnsignedRanges.insert(std::make_pair(S, CR));
if (!Pair.second)
Pair.first->second = CR;
return Pair.first->second;
}
/// setUnsignedRange - Set the memoized signed range for the given SCEV.
const ConstantRange &setSignedRange(const SCEV *S,
const ConstantRange &CR) {
std::pair<DenseMap<const SCEV *, ConstantRange>::iterator, bool> Pair =
SignedRanges.insert(std::make_pair(S, CR));
if (!Pair.second)
Pair.first->second = CR;
return Pair.first->second;
}
/// createSCEV - We know that there is no SCEV for the specified value.
/// Analyze the expression.
const SCEV *createSCEV(Value *V);
/// createNodeForPHI - Provide the special handling we need to analyze PHI
/// SCEVs.
const SCEV *createNodeForPHI(PHINode *PN);
/// createNodeForGEP - Provide the special handling we need to analyze GEP
/// SCEVs.
const SCEV *createNodeForGEP(GEPOperator *GEP);
/// computeSCEVAtScope - Implementation code for getSCEVAtScope; called
/// at most once for each SCEV+Loop pair.
///
const SCEV *computeSCEVAtScope(const SCEV *S, const Loop *L);
/// ForgetSymbolicValue - This looks up computed SCEV values for all
/// instructions that depend on the given instruction and removes them from
/// the ValueExprMap map if they reference SymName. This is used during PHI
/// resolution.
void ForgetSymbolicName(Instruction *I, const SCEV *SymName);
/// getBECount - Subtract the end and start values and divide by the step,
/// rounding up, to get the number of times the backedge is executed. Return
/// CouldNotCompute if an intermediate computation overflows.
const SCEV *getBECount(const SCEV *Start,
const SCEV *End,
const SCEV *Step,
bool NoWrap);
/// 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);
/// ComputeExitLimit - Compute the number of times the backedge of the
/// specified loop will execute if it exits via the specified block.
ExitLimit ComputeExitLimit(const Loop *L, BasicBlock *ExitingBlock);
/// ComputeExitLimitFromCond - Compute the number of times the backedge of
/// the specified loop will execute if its exit condition were a conditional
/// branch of ExitCond, TBB, and FBB.
ExitLimit ComputeExitLimitFromCond(const Loop *L,
Value *ExitCond,
BasicBlock *TBB,
BasicBlock *FBB);
/// ComputeExitLimitFromICmp - Compute the number of times the backedge of
/// the specified loop will execute if its exit condition were a conditional
/// branch of the ICmpInst ExitCond, TBB, and FBB.
ExitLimit ComputeExitLimitFromICmp(const Loop *L,
ICmpInst *ExitCond,
BasicBlock *TBB,
BasicBlock *FBB);
/// ComputeLoadConstantCompareExitLimit - Given an exit condition
/// of 'icmp op load X, cst', try to see if we can compute the
/// backedge-taken count.
ExitLimit ComputeLoadConstantCompareExitLimit(LoadInst *LI,
Constant *RHS,
const Loop *L,
ICmpInst::Predicate p);
/// ComputeExitCountExhaustively - If the loop 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 exit count of the loop, return CouldNotCompute.
const SCEV *ComputeExitCountExhaustively(const Loop *L,
Value *Cond,
bool ExitWhen);
/// HowFarToZero - Return the number of times an exit condition comparing
/// the specified value to zero will execute. If not computable, return
/// CouldNotCompute.
ExitLimit HowFarToZero(const SCEV *V, const Loop *L);
/// HowFarToNonZero - Return the number of times an exit condition checking
/// the specified value for nonzero will execute. If not computable, return
/// CouldNotCompute.
ExitLimit HowFarToNonZero(const SCEV *V, const Loop *L);
/// HowManyLessThans - Return the number of times an exit condition
/// containing the specified less-than comparison will execute. If not
/// computable, return CouldNotCompute. isSigned specifies whether the
/// less-than is signed.
ExitLimit HowManyLessThans(const SCEV *LHS, const SCEV *RHS,
const Loop *L, bool isSigned);
/// 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.
std::pair<BasicBlock *, BasicBlock *>
getPredecessorWithUniqueSuccessorForBB(BasicBlock *BB);
/// isImpliedCond - Test whether the condition described by Pred, LHS, and
/// RHS is true whenever the given FoundCondValue value evaluates to true.
bool isImpliedCond(ICmpInst::Predicate Pred,
const SCEV *LHS, const SCEV *RHS,
Value *FoundCondValue,
bool Inverse);
/// isImpliedCondOperands - Test whether the condition described by Pred,
/// LHS, and RHS is true whenever the condition described by Pred, FoundLHS,
/// and FoundRHS is true.
bool isImpliedCondOperands(ICmpInst::Predicate Pred,
const SCEV *LHS, const SCEV *RHS,
const SCEV *FoundLHS, const SCEV *FoundRHS);
/// isImpliedCondOperandsHelper - Test whether the condition described by
/// Pred, LHS, and RHS is true whenever the condition described by Pred,
/// FoundLHS, and FoundRHS is true.
bool isImpliedCondOperandsHelper(ICmpInst::Predicate Pred,
const SCEV *LHS, const SCEV *RHS,
const SCEV *FoundLHS,
const SCEV *FoundRHS);
/// 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);
/// isKnownPredicateWithRanges - Test if the given expression is known to
/// satisfy the condition described by Pred and the known constant ranges
/// of LHS and RHS.
///
bool isKnownPredicateWithRanges(ICmpInst::Predicate Pred,
const SCEV *LHS, const SCEV *RHS);
/// forgetMemoizedResults - Drop memoized information computed for S.
void forgetMemoizedResults(const SCEV *S);
public:
static char ID; // Pass identification, replacement for typeid
ScalarEvolution();
LLVMContext &getContext() const { return F->getContext(); }
/// 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(Type *Ty) const;
/// getTypeSizeInBits - Return the size in bits of the specified type,
/// for which isSCEVable must return true.
uint64_t getTypeSizeInBits(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.
Type *getEffectiveSCEVType(Type *Ty) const;
/// getSCEV - Return a SCEV expression for the full generality of the
/// specified expression.
const SCEV *getSCEV(Value *V);
const SCEV *getConstant(ConstantInt *V);
const SCEV *getConstant(const APInt& Val);
const SCEV *getConstant(Type *Ty, uint64_t V, bool isSigned = false);
const SCEV *getTruncateExpr(const SCEV *Op, Type *Ty);
const SCEV *getZeroExtendExpr(const SCEV *Op, Type *Ty);
const SCEV *getSignExtendExpr(const SCEV *Op, Type *Ty);
const SCEV *getAnyExtendExpr(const SCEV *Op, Type *Ty);
const SCEV *getAddExpr(SmallVectorImpl<const SCEV *> &Ops,
SCEV::NoWrapFlags Flags = SCEV::FlagAnyWrap);
const SCEV *getAddExpr(const SCEV *LHS, const SCEV *RHS,
SCEV::NoWrapFlags Flags = SCEV::FlagAnyWrap) {
SmallVector<const SCEV *, 2> Ops;
Ops.push_back(LHS);
Ops.push_back(RHS);
return getAddExpr(Ops, Flags);
}
const SCEV *getAddExpr(const SCEV *Op0, const SCEV *Op1, const SCEV *Op2,
SCEV::NoWrapFlags Flags = SCEV::FlagAnyWrap) {
SmallVector<const SCEV *, 3> Ops;
Ops.push_back(Op0);
Ops.push_back(Op1);
Ops.push_back(Op2);
return getAddExpr(Ops, Flags);
}
const SCEV *getMulExpr(SmallVectorImpl<const SCEV *> &Ops,
SCEV::NoWrapFlags Flags = SCEV::FlagAnyWrap);
const SCEV *getMulExpr(const SCEV *LHS, const SCEV *RHS,
SCEV::NoWrapFlags Flags = SCEV::FlagAnyWrap)
{
SmallVector<const SCEV *, 2> Ops;
Ops.push_back(LHS);
Ops.push_back(RHS);
return getMulExpr(Ops, Flags);
}
const SCEV *getMulExpr(const SCEV *Op0, const SCEV *Op1, const SCEV *Op2,
SCEV::NoWrapFlags Flags = SCEV::FlagAnyWrap) {
SmallVector<const SCEV *, 3> Ops;
Ops.push_back(Op0);
Ops.push_back(Op1);
Ops.push_back(Op2);
return getMulExpr(Ops, Flags);
}
const SCEV *getUDivExpr(const SCEV *LHS, const SCEV *RHS);
const SCEV *getAddRecExpr(const SCEV *Start, const SCEV *Step,
const Loop *L, SCEV::NoWrapFlags Flags);
const SCEV *getAddRecExpr(SmallVectorImpl<const SCEV *> &Operands,
const Loop *L, SCEV::NoWrapFlags Flags);
const SCEV *getAddRecExpr(const SmallVectorImpl<const SCEV *> &Operands,
const Loop *L, SCEV::NoWrapFlags Flags) {
SmallVector<const SCEV *, 4> NewOp(Operands.begin(), Operands.end());
return getAddRecExpr(NewOp, L, Flags);
}
const SCEV *getSMaxExpr(const SCEV *LHS, const SCEV *RHS);
const SCEV *getSMaxExpr(SmallVectorImpl<const SCEV *> &Operands);
const SCEV *getUMaxExpr(const SCEV *LHS, const SCEV *RHS);
const SCEV *getUMaxExpr(SmallVectorImpl<const SCEV *> &Operands);
const SCEV *getSMinExpr(const SCEV *LHS, const SCEV *RHS);
const SCEV *getUMinExpr(const SCEV *LHS, const SCEV *RHS);
const SCEV *getUnknown(Value *V);
const SCEV *getCouldNotCompute();
/// getSizeOfExpr - Return an expression for sizeof on the given type.
///
const SCEV *getSizeOfExpr(Type *AllocTy);
/// getAlignOfExpr - Return an expression for alignof on the given type.
///
const SCEV *getAlignOfExpr(Type *AllocTy);
/// getOffsetOfExpr - Return an expression for offsetof on the given field.
///
const SCEV *getOffsetOfExpr(StructType *STy, unsigned FieldNo);
/// getOffsetOfExpr - Return an expression for offsetof on the given field.
///
const SCEV *getOffsetOfExpr(Type *CTy, Constant *FieldNo);
/// getNegativeSCEV - Return the SCEV object corresponding to -V.
///
const SCEV *getNegativeSCEV(const SCEV *V);
/// getNotSCEV - Return the SCEV object corresponding to ~V.
///
const SCEV *getNotSCEV(const SCEV *V);
/// getMinusSCEV - Return LHS-RHS. Minus is represented in SCEV as A+B*-1.
const SCEV *getMinusSCEV(const SCEV *LHS, const SCEV *RHS,
SCEV::NoWrapFlags Flags = SCEV::FlagAnyWrap);
/// 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.
const SCEV *getTruncateOrZeroExtend(const SCEV *V, 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.
const SCEV *getTruncateOrSignExtend(const SCEV *V, 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.
const SCEV *getNoopOrZeroExtend(const SCEV *V, 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.
const SCEV *getNoopOrSignExtend(const SCEV *V, Type *Ty);
/// getNoopOrAnyExtend - Return a SCEV corresponding to a conversion of
/// the input value to the specified type. If the type must be extended,
/// it is extended with unspecified bits. The conversion must not be
/// narrowing.
const SCEV *getNoopOrAnyExtend(const SCEV *V, Type *Ty);
/// getTruncateOrNoop - Return a SCEV corresponding to a conversion of the
/// input value to the specified type. The conversion must not be
/// widening.
const SCEV *getTruncateOrNoop(const SCEV *V, Type *Ty);
/// getUMaxFromMismatchedTypes - Promote the operands to the wider of
/// the types using zero-extension, and then perform a umax operation
/// with them.
const SCEV *getUMaxFromMismatchedTypes(const SCEV *LHS,
const SCEV *RHS);
/// getUMinFromMismatchedTypes - Promote the operands to the wider of
/// the types using zero-extension, and then perform a umin operation
/// with them.
const SCEV *getUMinFromMismatchedTypes(const SCEV *LHS,
const SCEV *RHS);
/// getPointerBase - Transitively follow the chain of pointer-type operands
/// until reaching a SCEV that does not have a single pointer operand. This
/// returns a SCEVUnknown pointer for well-formed pointer-type expressions,
/// but corner cases do exist.
const SCEV *getPointerBase(const SCEV *V);
/// getSCEVAtScope - Return a SCEV expression 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.
const SCEV *getSCEVAtScope(const SCEV *S, const Loop *L);
/// getSCEVAtScope - This is a convenience function which does
/// getSCEVAtScope(getSCEV(V), L).
const SCEV *getSCEVAtScope(Value *V, const Loop *L);
/// isLoopEntryGuardedByCond - 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, and to eliminate casts.
bool isLoopEntryGuardedByCond(const Loop *L, ICmpInst::Predicate Pred,
const SCEV *LHS, const SCEV *RHS);
/// isLoopBackedgeGuardedByCond - Test whether the backedge of the loop is
/// protected by a conditional between LHS and RHS. This is used to
/// to eliminate casts.
bool isLoopBackedgeGuardedByCond(const Loop *L, ICmpInst::Predicate Pred,
const SCEV *LHS, const SCEV *RHS);
/// getSmallConstantTripCount - Returns the maximum trip count of this loop
/// as a normal unsigned value, if possible. Returns 0 if the trip count is
/// unknown or not constant.
unsigned getSmallConstantTripCount(Loop *L, BasicBlock *ExitBlock);
/// getSmallConstantTripMultiple - Returns the largest constant divisor of
/// the trip count of this loop as a normal unsigned value, if
/// possible. This means that the actual trip count is always a multiple of
/// the returned value (don't forget the trip count could very well be zero
/// as well!).
unsigned getSmallConstantTripMultiple(Loop *L, BasicBlock *ExitBlock);
// getExitCount - Get the expression for the number of loop iterations for
// which this loop is guaranteed not to exit via ExitingBlock. Otherwise
// return SCEVCouldNotCompute.
const SCEV *getExitCount(Loop *L, BasicBlock *ExitingBlock);
/// 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).
///
const SCEV *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.
const SCEV *getMaxBackedgeTakenCount(const Loop *L);
/// hasLoopInvariantBackedgeTakenCount - Return true if the specified loop
/// has an analyzable loop-invariant backedge-taken count.
bool hasLoopInvariantBackedgeTakenCount(const Loop *L);
/// forgetLoop - 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 forgetLoop(const Loop *L);
/// forgetValue - This method should be called by the client when it has
/// changed a value in a way that may effect its value, or which may
/// disconnect it from a def-use chain linking it to a loop.
void forgetValue(Value *V);
/// GetMinTrailingZeros - Determine the minimum number of zero bits that S
/// is guaranteed to end in (at every loop iteration). It is, at the same
/// time, the minimum number of times S is divisible by 2. For example,
/// given {4,+,8} it returns 2. If S is guaranteed to be 0, it returns the
/// bitwidth of S.
uint32_t GetMinTrailingZeros(const SCEV *S);
/// getUnsignedRange - Determine the unsigned range for a particular SCEV.
///
ConstantRange getUnsignedRange(const SCEV *S);
/// getSignedRange - Determine the signed range for a particular SCEV.
///
ConstantRange getSignedRange(const SCEV *S);
/// isKnownNegative - Test if the given expression is known to be negative.
///
bool isKnownNegative(const SCEV *S);
/// isKnownPositive - Test if the given expression is known to be positive.
///
bool isKnownPositive(const SCEV *S);
/// isKnownNonNegative - Test if the given expression is known to be
/// non-negative.
///
bool isKnownNonNegative(const SCEV *S);
/// isKnownNonPositive - Test if the given expression is known to be
/// non-positive.
///
bool isKnownNonPositive(const SCEV *S);
/// isKnownNonZero - Test if the given expression is known to be
/// non-zero.
///
bool isKnownNonZero(const SCEV *S);
/// isKnownPredicate - Test if the given expression is known to satisfy
/// the condition described by Pred, LHS, and RHS.
///
bool isKnownPredicate(ICmpInst::Predicate Pred,
const SCEV *LHS, const SCEV *RHS);
/// SimplifyICmpOperands - Simplify LHS and RHS in a comparison with
/// predicate Pred. Return true iff any changes were made. If the
/// operands are provably equal or inequal, LHS and RHS are set to
/// the same value and Pred is set to either ICMP_EQ or ICMP_NE.
///
bool SimplifyICmpOperands(ICmpInst::Predicate &Pred,
const SCEV *&LHS,
const SCEV *&RHS);
/// getLoopDisposition - Return the "disposition" of the given SCEV with
/// respect to the given loop.
LoopDisposition getLoopDisposition(const SCEV *S, const Loop *L);
/// isLoopInvariant - Return true if the value of the given SCEV is
/// unchanging in the specified loop.
bool isLoopInvariant(const SCEV *S, const Loop *L);
/// hasComputableLoopEvolution - Return true if the given 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.
bool hasComputableLoopEvolution(const SCEV *S, const Loop *L);
/// getLoopDisposition - Return the "disposition" of the given SCEV with
/// respect to the given block.
BlockDisposition getBlockDisposition(const SCEV *S, const BasicBlock *BB);
/// dominates - Return true if elements that makes up the given SCEV
/// dominate the specified basic block.
bool dominates(const SCEV *S, const BasicBlock *BB);
/// properlyDominates - Return true if elements that makes up the given SCEV
/// properly dominate the specified basic block.
bool properlyDominates(const SCEV *S, const BasicBlock *BB);
/// hasOperand - Test whether the given SCEV has Op as a direct or
/// indirect operand.
bool hasOperand(const SCEV *S, const SCEV *Op) const;
virtual bool runOnFunction(Function &F);
virtual void releaseMemory();
virtual void getAnalysisUsage(AnalysisUsage &AU) const;
virtual void print(raw_ostream &OS, const Module* = 0) const;
private:
FoldingSet<SCEV> UniqueSCEVs;
BumpPtrAllocator SCEVAllocator;
/// FirstUnknown - The head of a linked list of all SCEVUnknown
/// values that have been allocated. This is used by releaseMemory
/// to locate them all and call their destructors.
SCEVUnknown *FirstUnknown;
};
}
#endif
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