| //===- llvm/Transforms/Utils/LoopUtils.h - Loop utilities -*- 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 some loop transformation utilities. |
| // |
| //===----------------------------------------------------------------------===// |
| |
| #ifndef LLVM_TRANSFORMS_UTILS_LOOPUTILS_H |
| #define LLVM_TRANSFORMS_UTILS_LOOPUTILS_H |
| |
| #include "llvm/ADT/SmallVector.h" |
| #include "llvm/Analysis/AliasAnalysis.h" |
| #include "llvm/IR/Dominators.h" |
| #include "llvm/IR/IRBuilder.h" |
| |
| namespace llvm { |
| class AliasSet; |
| class AliasSetTracker; |
| class AssumptionCache; |
| class BasicBlock; |
| class DataLayout; |
| class DominatorTree; |
| class Loop; |
| class LoopInfo; |
| class Pass; |
| class PredIteratorCache; |
| class ScalarEvolution; |
| class TargetLibraryInfo; |
| |
| /// \brief Captures loop safety information. |
| /// It keep information for loop & its header may throw exception. |
| struct LICMSafetyInfo { |
| bool MayThrow; // The current loop contains an instruction which |
| // may throw. |
| bool HeaderMayThrow; // Same as previous, but specific to loop header |
| LICMSafetyInfo() : MayThrow(false), HeaderMayThrow(false) |
| {} |
| }; |
| |
| /// The RecurrenceDescriptor is used to identify recurrences variables in a |
| /// loop. Reduction is a special case of recurrence that has uses of the |
| /// recurrence variable outside the loop. The method isReductionPHI identifies |
| /// reductions that are basic recurrences. |
| /// |
| /// Basic recurrences are defined as the summation, product, OR, AND, XOR, min, |
| /// or max of a set of terms. For example: for(i=0; i<n; i++) { total += |
| /// array[i]; } is a summation of array elements. Basic recurrences are a |
| /// special case of chains of recurrences (CR). See ScalarEvolution for CR |
| /// references. |
| |
| /// This struct holds information about recurrence variables. |
| class RecurrenceDescriptor { |
| |
| public: |
| /// This enum represents the kinds of recurrences that we support. |
| enum RecurrenceKind { |
| RK_NoRecurrence, ///< Not a recurrence. |
| RK_IntegerAdd, ///< Sum of integers. |
| RK_IntegerMult, ///< Product of integers. |
| RK_IntegerOr, ///< Bitwise or logical OR of numbers. |
| RK_IntegerAnd, ///< Bitwise or logical AND of numbers. |
| RK_IntegerXor, ///< Bitwise or logical XOR of numbers. |
| RK_IntegerMinMax, ///< Min/max implemented in terms of select(cmp()). |
| RK_FloatAdd, ///< Sum of floats. |
| RK_FloatMult, ///< Product of floats. |
| RK_FloatMinMax ///< Min/max implemented in terms of select(cmp()). |
| }; |
| |
| // This enum represents the kind of minmax recurrence. |
| enum MinMaxRecurrenceKind { |
| MRK_Invalid, |
| MRK_UIntMin, |
| MRK_UIntMax, |
| MRK_SIntMin, |
| MRK_SIntMax, |
| MRK_FloatMin, |
| MRK_FloatMax |
| }; |
| |
| RecurrenceDescriptor() |
| : StartValue(nullptr), LoopExitInstr(nullptr), Kind(RK_NoRecurrence), |
| MinMaxKind(MRK_Invalid), UnsafeAlgebraInst(nullptr), |
| RecurrenceType(nullptr), IsSigned(false) {} |
| |
| RecurrenceDescriptor(Value *Start, Instruction *Exit, RecurrenceKind K, |
| MinMaxRecurrenceKind MK, Instruction *UAI, Type *RT, |
| bool Signed, SmallPtrSetImpl<Instruction *> &CI) |
| : StartValue(Start), LoopExitInstr(Exit), Kind(K), MinMaxKind(MK), |
| UnsafeAlgebraInst(UAI), RecurrenceType(RT), IsSigned(Signed) { |
| CastInsts.insert(CI.begin(), CI.end()); |
| } |
| |
| /// This POD struct holds information about a potential recurrence operation. |
| class InstDesc { |
| |
| public: |
| InstDesc(bool IsRecur, Instruction *I, Instruction *UAI = nullptr) |
| : IsRecurrence(IsRecur), PatternLastInst(I), MinMaxKind(MRK_Invalid), |
| UnsafeAlgebraInst(UAI) {} |
| |
| InstDesc(Instruction *I, MinMaxRecurrenceKind K, Instruction *UAI = nullptr) |
| : IsRecurrence(true), PatternLastInst(I), MinMaxKind(K), |
| UnsafeAlgebraInst(UAI) {} |
| |
| bool isRecurrence() { return IsRecurrence; } |
| |
| bool hasUnsafeAlgebra() { return UnsafeAlgebraInst != nullptr; } |
| |
| Instruction *getUnsafeAlgebraInst() { return UnsafeAlgebraInst; } |
| |
| MinMaxRecurrenceKind getMinMaxKind() { return MinMaxKind; } |
| |
| Instruction *getPatternInst() { return PatternLastInst; } |
| |
| private: |
| // Is this instruction a recurrence candidate. |
| bool IsRecurrence; |
| // The last instruction in a min/max pattern (select of the select(icmp()) |
| // pattern), or the current recurrence instruction otherwise. |
| Instruction *PatternLastInst; |
| // If this is a min/max pattern the comparison predicate. |
| MinMaxRecurrenceKind MinMaxKind; |
| // Recurrence has unsafe algebra. |
| Instruction *UnsafeAlgebraInst; |
| }; |
| |
| /// Returns a struct describing if the instruction 'I' can be a recurrence |
| /// variable of type 'Kind'. If the recurrence is a min/max pattern of |
| /// select(icmp()) this function advances the instruction pointer 'I' from the |
| /// compare instruction to the select instruction and stores this pointer in |
| /// 'PatternLastInst' member of the returned struct. |
| static InstDesc isRecurrenceInstr(Instruction *I, RecurrenceKind Kind, |
| InstDesc &Prev, bool HasFunNoNaNAttr); |
| |
| /// Returns true if instruction I has multiple uses in Insts |
| static bool hasMultipleUsesOf(Instruction *I, |
| SmallPtrSetImpl<Instruction *> &Insts); |
| |
| /// Returns true if all uses of the instruction I is within the Set. |
| static bool areAllUsesIn(Instruction *I, SmallPtrSetImpl<Instruction *> &Set); |
| |
| /// Returns a struct describing if the instruction if the instruction is a |
| /// Select(ICmp(X, Y), X, Y) instruction pattern corresponding to a min(X, Y) |
| /// or max(X, Y). |
| static InstDesc isMinMaxSelectCmpPattern(Instruction *I, InstDesc &Prev); |
| |
| /// Returns identity corresponding to the RecurrenceKind. |
| static Constant *getRecurrenceIdentity(RecurrenceKind K, Type *Tp); |
| |
| /// Returns the opcode of binary operation corresponding to the |
| /// RecurrenceKind. |
| static unsigned getRecurrenceBinOp(RecurrenceKind Kind); |
| |
| /// Returns a Min/Max operation corresponding to MinMaxRecurrenceKind. |
| static Value *createMinMaxOp(IRBuilder<> &Builder, MinMaxRecurrenceKind RK, |
| Value *Left, Value *Right); |
| |
| /// Returns true if Phi is a reduction of type Kind and adds it to the |
| /// RecurrenceDescriptor. |
| static bool AddReductionVar(PHINode *Phi, RecurrenceKind Kind, Loop *TheLoop, |
| bool HasFunNoNaNAttr, |
| RecurrenceDescriptor &RedDes); |
| |
| /// Returns true if Phi is a reduction in TheLoop. The RecurrenceDescriptor is |
| /// returned in RedDes. |
| static bool isReductionPHI(PHINode *Phi, Loop *TheLoop, |
| RecurrenceDescriptor &RedDes); |
| |
| RecurrenceKind getRecurrenceKind() { return Kind; } |
| |
| MinMaxRecurrenceKind getMinMaxRecurrenceKind() { return MinMaxKind; } |
| |
| TrackingVH<Value> getRecurrenceStartValue() { return StartValue; } |
| |
| Instruction *getLoopExitInstr() { return LoopExitInstr; } |
| |
| /// Returns true if the recurrence has unsafe algebra which requires a relaxed |
| /// floating-point model. |
| bool hasUnsafeAlgebra() { return UnsafeAlgebraInst != nullptr; } |
| |
| /// Returns first unsafe algebra instruction in the PHI node's use-chain. |
| Instruction *getUnsafeAlgebraInst() { return UnsafeAlgebraInst; } |
| |
| /// Returns true if the recurrence kind is an integer kind. |
| static bool isIntegerRecurrenceKind(RecurrenceKind Kind); |
| |
| /// Returns true if the recurrence kind is a floating point kind. |
| static bool isFloatingPointRecurrenceKind(RecurrenceKind Kind); |
| |
| /// Returns true if the recurrence kind is an arithmetic kind. |
| static bool isArithmeticRecurrenceKind(RecurrenceKind Kind); |
| |
| /// Determines if Phi may have been type-promoted. If Phi has a single user |
| /// that ANDs the Phi with a type mask, return the user. RT is updated to |
| /// account for the narrower bit width represented by the mask, and the AND |
| /// instruction is added to CI. |
| static Instruction *lookThroughAnd(PHINode *Phi, Type *&RT, |
| SmallPtrSetImpl<Instruction *> &Visited, |
| SmallPtrSetImpl<Instruction *> &CI); |
| |
| /// Returns true if all the source operands of a recurrence are either |
| /// SExtInsts or ZExtInsts. This function is intended to be used with |
| /// lookThroughAnd to determine if the recurrence has been type-promoted. The |
| /// source operands are added to CI, and IsSigned is updated to indicate if |
| /// all source operands are SExtInsts. |
| static bool getSourceExtensionKind(Instruction *Start, Instruction *Exit, |
| Type *RT, bool &IsSigned, |
| SmallPtrSetImpl<Instruction *> &Visited, |
| SmallPtrSetImpl<Instruction *> &CI); |
| |
| /// Returns the type of the recurrence. This type can be narrower than the |
| /// actual type of the Phi if the recurrence has been type-promoted. |
| Type *getRecurrenceType() { return RecurrenceType; } |
| |
| /// Returns a reference to the instructions used for type-promoting the |
| /// recurrence. |
| SmallPtrSet<Instruction *, 8> &getCastInsts() { return CastInsts; } |
| |
| /// Returns true if all source operands of the recurrence are SExtInsts. |
| bool isSigned() { return IsSigned; } |
| |
| private: |
| // The starting value of the recurrence. |
| // It does not have to be zero! |
| TrackingVH<Value> StartValue; |
| // The instruction who's value is used outside the loop. |
| Instruction *LoopExitInstr; |
| // The kind of the recurrence. |
| RecurrenceKind Kind; |
| // If this a min/max recurrence the kind of recurrence. |
| MinMaxRecurrenceKind MinMaxKind; |
| // First occurance of unasfe algebra in the PHI's use-chain. |
| Instruction *UnsafeAlgebraInst; |
| // The type of the recurrence. |
| Type *RecurrenceType; |
| // True if all source operands of the recurrence are SExtInsts. |
| bool IsSigned; |
| // Instructions used for type-promoting the recurrence. |
| SmallPtrSet<Instruction *, 8> CastInsts; |
| }; |
| |
| /// A struct for saving information about induction variables. |
| class InductionDescriptor { |
| public: |
| /// This enum represents the kinds of inductions that we support. |
| enum InductionKind { |
| IK_NoInduction, ///< Not an induction variable. |
| IK_IntInduction, ///< Integer induction variable. Step = C. |
| IK_PtrInduction ///< Pointer induction var. Step = C / sizeof(elem). |
| }; |
| |
| public: |
| /// Default constructor - creates an invalid induction. |
| InductionDescriptor() |
| : StartValue(nullptr), IK(IK_NoInduction), StepValue(nullptr) {} |
| |
| /// Get the consecutive direction. Returns: |
| /// 0 - unknown or non-consecutive. |
| /// 1 - consecutive and increasing. |
| /// -1 - consecutive and decreasing. |
| int getConsecutiveDirection() const; |
| |
| /// Compute the transformed value of Index at offset StartValue using step |
| /// StepValue. |
| /// For integer induction, returns StartValue + Index * StepValue. |
| /// For pointer induction, returns StartValue[Index * StepValue]. |
| /// FIXME: The newly created binary instructions should contain nsw/nuw |
| /// flags, which can be found from the original scalar operations. |
| Value *transform(IRBuilder<> &B, Value *Index) const; |
| |
| Value *getStartValue() const { return StartValue; } |
| InductionKind getKind() const { return IK; } |
| ConstantInt *getStepValue() const { return StepValue; } |
| |
| static bool isInductionPHI(PHINode *Phi, ScalarEvolution *SE, |
| InductionDescriptor &D); |
| |
| private: |
| /// Private constructor - used by \c isInductionPHI. |
| InductionDescriptor(Value *Start, InductionKind K, ConstantInt *Step); |
| |
| /// Start value. |
| TrackingVH<Value> StartValue; |
| /// Induction kind. |
| InductionKind IK; |
| /// Step value. |
| ConstantInt *StepValue; |
| }; |
| |
| BasicBlock *InsertPreheaderForLoop(Loop *L, DominatorTree *DT, LoopInfo *LI, |
| bool PreserveLCSSA); |
| |
| /// \brief Simplify each loop in a loop nest recursively. |
| /// |
| /// This takes a potentially un-simplified loop L (and its children) and turns |
| /// it into a simplified loop nest with preheaders and single backedges. It will |
| /// update \c AliasAnalysis and \c ScalarEvolution analyses if they're non-null. |
| bool simplifyLoop(Loop *L, DominatorTree *DT, LoopInfo *LI, ScalarEvolution *SE, |
| AssumptionCache *AC, bool PreserveLCSSA); |
| |
| /// \brief Put loop into LCSSA form. |
| /// |
| /// Looks at all instructions in the loop which have uses outside of the |
| /// current loop. For each, an LCSSA PHI node is inserted and the uses outside |
| /// the loop are rewritten to use this node. |
| /// |
| /// LoopInfo and DominatorTree are required and preserved. |
| /// |
| /// If ScalarEvolution is passed in, it will be preserved. |
| /// |
| /// Returns true if any modifications are made to the loop. |
| bool formLCSSA(Loop &L, DominatorTree &DT, LoopInfo *LI, |
| ScalarEvolution *SE); |
| |
| /// \brief Put a loop nest into LCSSA form. |
| /// |
| /// This recursively forms LCSSA for a loop nest. |
| /// |
| /// LoopInfo and DominatorTree are required and preserved. |
| /// |
| /// If ScalarEvolution is passed in, it will be preserved. |
| /// |
| /// Returns true if any modifications are made to the loop. |
| bool formLCSSARecursively(Loop &L, DominatorTree &DT, LoopInfo *LI, |
| ScalarEvolution *SE); |
| |
| /// \brief Walk the specified region of the CFG (defined by all blocks |
| /// dominated by the specified block, and that are in the current loop) in |
| /// reverse depth first order w.r.t the DominatorTree. This allows us to visit |
| /// uses before definitions, allowing us to sink a loop body in one pass without |
| /// iteration. Takes DomTreeNode, AliasAnalysis, LoopInfo, DominatorTree, |
| /// DataLayout, TargetLibraryInfo, Loop, AliasSet information for all |
| /// instructions of the loop and loop safety information as arguments. |
| /// It returns changed status. |
| bool sinkRegion(DomTreeNode *, AliasAnalysis *, LoopInfo *, DominatorTree *, |
| TargetLibraryInfo *, Loop *, AliasSetTracker *, |
| LICMSafetyInfo *); |
| |
| /// \brief Walk the specified region of the CFG (defined by all blocks |
| /// dominated by the specified block, and that are in the current loop) in depth |
| /// first order w.r.t the DominatorTree. This allows us to visit definitions |
| /// before uses, allowing us to hoist a loop body in one pass without iteration. |
| /// Takes DomTreeNode, AliasAnalysis, LoopInfo, DominatorTree, DataLayout, |
| /// TargetLibraryInfo, Loop, AliasSet information for all instructions of the |
| /// loop and loop safety information as arguments. It returns changed status. |
| bool hoistRegion(DomTreeNode *, AliasAnalysis *, LoopInfo *, DominatorTree *, |
| TargetLibraryInfo *, Loop *, AliasSetTracker *, |
| LICMSafetyInfo *); |
| |
| /// \brief Try to promote memory values to scalars by sinking stores out of |
| /// the loop and moving loads to before the loop. We do this by looping over |
| /// the stores in the loop, looking for stores to Must pointers which are |
| /// loop invariant. It takes AliasSet, Loop exit blocks vector, loop exit blocks |
| /// insertion point vector, PredIteratorCache, LoopInfo, DominatorTree, Loop, |
| /// AliasSet information for all instructions of the loop and loop safety |
| /// information as arguments. It returns changed status. |
| bool promoteLoopAccessesToScalars(AliasSet &, SmallVectorImpl<BasicBlock*> &, |
| SmallVectorImpl<Instruction*> &, |
| PredIteratorCache &, LoopInfo *, |
| DominatorTree *, Loop *, AliasSetTracker *, |
| LICMSafetyInfo *); |
| |
| /// \brief Computes safety information for a loop |
| /// checks loop body & header for the possibility of may throw |
| /// exception, it takes LICMSafetyInfo and loop as argument. |
| /// Updates safety information in LICMSafetyInfo argument. |
| void computeLICMSafetyInfo(LICMSafetyInfo *, Loop *); |
| |
| /// \brief Returns the instructions that use values defined in the loop. |
| SmallVector<Instruction *, 8> findDefsUsedOutsideOfLoop(Loop *L); |
| } |
| |
| #endif |