//===- llvm/Analysis/TargetTransformInfo.h ----------------------*- C++ -*-===// // // The LLVM Compiler Infrastructure // // This file is distributed under the University of Illinois Open Source // License. See LICENSE.TXT for details. // //===----------------------------------------------------------------------===// // // This pass exposes codegen information to IR-level passes. Every // transformation that uses codegen information is broken into three parts: // 1. The IR-level analysis pass. // 2. The IR-level transformation interface which provides the needed // information. // 3. Codegen-level implementation which uses target-specific hooks. // // This file defines #2, which is the interface that IR-level transformations // use for querying the codegen. // //===----------------------------------------------------------------------===// #ifndef LLVM_ANALYSIS_TARGETTRANSFORMINFO_H #define LLVM_ANALYSIS_TARGETTRANSFORMINFO_H #include "llvm/IR/Intrinsics.h" #include "llvm/Pass.h" #include "llvm/Support/DataTypes.h" namespace llvm { class GlobalValue; class Loop; class Type; class User; class Value; /// TargetTransformInfo - This pass provides access to the codegen /// interfaces that are needed for IR-level transformations. class TargetTransformInfo { protected: /// \brief The TTI instance one level down the stack. /// /// This is used to implement the default behavior all of the methods which /// is to delegate up through the stack of TTIs until one can answer the /// query. TargetTransformInfo *PrevTTI; /// \brief The top of the stack of TTI analyses available. /// /// This is a convenience routine maintained as TTI analyses become available /// that complements the PrevTTI delegation chain. When one part of an /// analysis pass wants to query another part of the analysis pass it can use /// this to start back at the top of the stack. TargetTransformInfo *TopTTI; /// All pass subclasses must in their initializePass routine call /// pushTTIStack with themselves to update the pointers tracking the previous /// TTI instance in the analysis group's stack, and the top of the analysis /// group's stack. void pushTTIStack(Pass *P); /// All pass subclasses must in their finalizePass routine call popTTIStack /// to update the pointers tracking the previous TTI instance in the analysis /// group's stack, and the top of the analysis group's stack. void popTTIStack(); /// All pass subclasses must call TargetTransformInfo::getAnalysisUsage. virtual void getAnalysisUsage(AnalysisUsage &AU) const; public: /// This class is intended to be subclassed by real implementations. virtual ~TargetTransformInfo() = 0; /// \name Generic Target Information /// @{ /// \brief Underlying constants for 'cost' values in this interface. /// /// Many APIs in this interface return a cost. This enum defines the /// fundamental values that should be used to interpret (and produce) those /// costs. The costs are returned as an unsigned rather than a member of this /// enumeration because it is expected that the cost of one IR instruction /// may have a multiplicative factor to it or otherwise won't fit directly /// into the enum. Moreover, it is common to sum or average costs which works /// better as simple integral values. Thus this enum only provides constants. /// /// Note that these costs should usually reflect the intersection of code-size /// cost and execution cost. A free instruction is typically one that folds /// into another instruction. For example, reg-to-reg moves can often be /// skipped by renaming the registers in the CPU, but they still are encoded /// and thus wouldn't be considered 'free' here. enum TargetCostConstants { TCC_Free = 0, ///< Expected to fold away in lowering. TCC_Basic = 1, ///< The cost of a typical 'add' instruction. TCC_Load = 3, TCC_Expensive = 4 ///< The cost of a 'div' instruction on x86. }; /// \brief Estimate the cost of a specific operation when lowered. /// /// Note that this is designed to work on an arbitrary synthetic opcode, and /// thus work for hypothetical queries before an instruction has even been /// formed. However, this does *not* work for GEPs, and must not be called /// for a GEP instruction. Instead, use the dedicated getGEPCost interface as /// analyzing a GEP's cost required more information. /// /// Typically only the result type is required, and the operand type can be /// omitted. However, if the opcode is one of the cast instructions, the /// operand type is required. /// /// The returned cost is defined in terms of \c TargetCostConstants, see its /// comments for a detailed explanation of the cost values. virtual unsigned getOperationCost(unsigned Opcode, Type *Ty, Type *OpTy = 0) const; /// \brief Estimate the cost of a GEP operation when lowered. /// /// The contract for this function is the same as \c getOperationCost except /// that it supports an interface that provides extra information specific to /// the GEP operation. virtual unsigned getGEPCost(const Value *Ptr, ArrayRef<const Value *> Operands) const; /// \brief Estimate the cost of a function call when lowered. /// /// The contract for this is the same as \c getOperationCost except that it /// supports an interface that provides extra information specific to call /// instructions. /// /// This is the most basic query for estimating call cost: it only knows the /// function type and (potentially) the number of arguments at the call site. /// The latter is only interesting for varargs function types. virtual unsigned getCallCost(FunctionType *FTy, int NumArgs = -1) const; /// \brief Estimate the cost of calling a specific function when lowered. /// /// This overload adds the ability to reason about the particular function /// being called in the event it is a library call with special lowering. virtual unsigned getCallCost(const Function *F, int NumArgs = -1) const; /// \brief Estimate the cost of calling a specific function when lowered. /// /// This overload allows specifying a set of candidate argument values. virtual unsigned getCallCost(const Function *F, ArrayRef<const Value *> Arguments) const; /// \brief Estimate the cost of an intrinsic when lowered. /// /// Mirrors the \c getCallCost method but uses an intrinsic identifier. virtual unsigned getIntrinsicCost(Intrinsic::ID IID, Type *RetTy, ArrayRef<Type *> ParamTys) const; /// \brief Estimate the cost of an intrinsic when lowered. /// /// Mirrors the \c getCallCost method but uses an intrinsic identifier. virtual unsigned getIntrinsicCost(Intrinsic::ID IID, Type *RetTy, ArrayRef<const Value *> Arguments) const; /// \brief Estimate the cost of a given IR user when lowered. /// /// This can estimate the cost of either a ConstantExpr or Instruction when /// lowered. It has two primary advantages over the \c getOperationCost and /// \c getGEPCost above, and one significant disadvantage: it can only be /// used when the IR construct has already been formed. /// /// The advantages are that it can inspect the SSA use graph to reason more /// accurately about the cost. For example, all-constant-GEPs can often be /// folded into a load or other instruction, but if they are used in some /// other context they may not be folded. This routine can distinguish such /// cases. /// /// The returned cost is defined in terms of \c TargetCostConstants, see its /// comments for a detailed explanation of the cost values. virtual unsigned getUserCost(const User *U) const; /// \brief hasBranchDivergence - Return true if branch divergence exists. /// Branch divergence has a significantly negative impact on GPU performance /// when threads in the same wavefront take different paths due to conditional /// branches. virtual bool hasBranchDivergence() const; /// \brief Test whether calls to a function lower to actual program function /// calls. /// /// The idea is to test whether the program is likely to require a 'call' /// instruction or equivalent in order to call the given function. /// /// FIXME: It's not clear that this is a good or useful query API. Client's /// should probably move to simpler cost metrics using the above. /// Alternatively, we could split the cost interface into distinct code-size /// and execution-speed costs. This would allow modelling the core of this /// query more accurately as the a call is a single small instruction, but /// incurs significant execution cost. virtual bool isLoweredToCall(const Function *F) const; /// Parameters that control the generic loop unrolling transformation. struct UnrollingPreferences { /// The cost threshold for the unrolled loop, compared to /// CodeMetrics.NumInsts aggregated over all basic blocks in the loop body. /// The unrolling factor is set such that the unrolled loop body does not /// exceed this cost. Set this to UINT_MAX to disable the loop body cost /// restriction. unsigned Threshold; /// The cost threshold for the unrolled loop when optimizing for size (set /// to UINT_MAX to disable). unsigned OptSizeThreshold; /// A forced unrolling factor (the number of concatenated bodies of the /// original loop in the unrolled loop body). When set to 0, the unrolling /// transformation will select an unrolling factor based on the current cost /// threshold and other factors. unsigned Count; /// Allow partial unrolling (unrolling of loops to expand the size of the /// loop body, not only to eliminate small constant-trip-count loops). bool Partial; /// Allow runtime unrolling (unrolling of loops to expand the size of the /// loop body even when the number of loop iterations is not known at compile /// time). bool Runtime; }; /// \brief Get target-customized preferences for the generic loop unrolling /// transformation. The caller will initialize UP with the current /// target-independent defaults. virtual void getUnrollingPreferences(Loop *L, UnrollingPreferences &UP) const; /// @} /// \name Scalar Target Information /// @{ /// \brief Flags indicating the kind of support for population count. /// /// Compared to the SW implementation, HW support is supposed to /// significantly boost the performance when the population is dense, and it /// may or may not degrade performance if the population is sparse. A HW /// support is considered as "Fast" if it can outperform, or is on a par /// with, SW implementation when the population is sparse; otherwise, it is /// considered as "Slow". enum PopcntSupportKind { PSK_Software, PSK_SlowHardware, PSK_FastHardware }; /// \brief Return true if the specified immediate is legal add immediate, that /// is the target has add instructions which can add a register with the /// immediate without having to materialize the immediate into a register. virtual bool isLegalAddImmediate(int64_t Imm) const; /// \brief Return true if the specified immediate is legal icmp immediate, /// that is the target has icmp instructions which can compare a register /// against the immediate without having to materialize the immediate into a /// register. virtual bool isLegalICmpImmediate(int64_t Imm) const; /// \brief Return true if the addressing mode represented by AM is legal for /// this target, for a load/store of the specified type. /// The type may be VoidTy, in which case only return true if the addressing /// mode is legal for a load/store of any legal type. /// TODO: Handle pre/postinc as well. virtual bool isLegalAddressingMode(Type *Ty, GlobalValue *BaseGV, int64_t BaseOffset, bool HasBaseReg, int64_t Scale) const; /// \brief Return the cost of the scaling factor used in the addressing /// mode represented by AM for this target, for a load/store /// of the specified type. /// If the AM is supported, the return value must be >= 0. /// If the AM is not supported, it returns a negative value. /// TODO: Handle pre/postinc as well. virtual int getScalingFactorCost(Type *Ty, GlobalValue *BaseGV, int64_t BaseOffset, bool HasBaseReg, int64_t Scale) const; /// \brief Return true if it's free to truncate a value of type Ty1 to type /// Ty2. e.g. On x86 it's free to truncate a i32 value in register EAX to i16 /// by referencing its sub-register AX. virtual bool isTruncateFree(Type *Ty1, Type *Ty2) const; /// \brief Return true if this type is legal. virtual bool isTypeLegal(Type *Ty) const; /// \brief Returns the target's jmp_buf alignment in bytes. virtual unsigned getJumpBufAlignment() const; /// \brief Returns the target's jmp_buf size in bytes. virtual unsigned getJumpBufSize() const; /// \brief Return true if switches should be turned into lookup tables for the /// target. virtual bool shouldBuildLookupTables() const; /// \brief Return hardware support for population count. virtual PopcntSupportKind getPopcntSupport(unsigned IntTyWidthInBit) const; /// \brief Return true if the hardware has a fast square-root instruction. virtual bool haveFastSqrt(Type *Ty) const; /// \brief Return the expected cost of materializing for the given integer /// immediate of the specified type. virtual unsigned getIntImmCost(const APInt &Imm, Type *Ty) const; /// \brief Return the expected cost of materialization for the given integer /// immediate of the specified type for a given instruction. The cost can be /// zero if the immediate can be folded into the specified instruction. virtual unsigned getIntImmCost(unsigned Opc, unsigned Idx, const APInt &Imm, Type *Ty) const; virtual unsigned getIntImmCost(Intrinsic::ID IID, unsigned Idx, const APInt &Imm, Type *Ty) const; /// @} /// \name Vector Target Information /// @{ /// \brief The various kinds of shuffle patterns for vector queries. enum ShuffleKind { SK_Broadcast, ///< Broadcast element 0 to all other elements. SK_Reverse, ///< Reverse the order of the vector. SK_InsertSubvector, ///< InsertSubvector. Index indicates start offset. SK_ExtractSubvector ///< ExtractSubvector Index indicates start offset. }; /// \brief Additional information about an operand's possible values. enum OperandValueKind { OK_AnyValue, // Operand can have any value. OK_UniformValue, // Operand is uniform (splat of a value). OK_UniformConstantValue, // Operand is uniform constant. OK_NonUniformConstantValue // Operand is a non uniform constant value. }; /// \return The number of scalar or vector registers that the target has. /// If 'Vectors' is true, it returns the number of vector registers. If it is /// set to false, it returns the number of scalar registers. virtual unsigned getNumberOfRegisters(bool Vector) const; /// \return The width of the largest scalar or vector register type. virtual unsigned getRegisterBitWidth(bool Vector) const; /// \return The maximum unroll factor that the vectorizer should try to /// perform for this target. This number depends on the level of parallelism /// and the number of execution units in the CPU. virtual unsigned getMaximumUnrollFactor() const; /// \return The expected cost of arithmetic ops, such as mul, xor, fsub, etc. virtual unsigned getArithmeticInstrCost(unsigned Opcode, Type *Ty, OperandValueKind Opd1Info = OK_AnyValue, OperandValueKind Opd2Info = OK_AnyValue) const; /// \return The cost of a shuffle instruction of kind Kind and of type Tp. /// The index and subtype parameters are used by the subvector insertion and /// extraction shuffle kinds. virtual unsigned getShuffleCost(ShuffleKind Kind, Type *Tp, int Index = 0, Type *SubTp = 0) const; /// \return The expected cost of cast instructions, such as bitcast, trunc, /// zext, etc. virtual unsigned getCastInstrCost(unsigned Opcode, Type *Dst, Type *Src) const; /// \return The expected cost of control-flow related instructions such as /// Phi, Ret, Br. virtual unsigned getCFInstrCost(unsigned Opcode) const; /// \returns The expected cost of compare and select instructions. virtual unsigned getCmpSelInstrCost(unsigned Opcode, Type *ValTy, Type *CondTy = 0) const; /// \return The expected cost of vector Insert and Extract. /// Use -1 to indicate that there is no information on the index value. virtual unsigned getVectorInstrCost(unsigned Opcode, Type *Val, unsigned Index = -1) const; /// \return The cost of Load and Store instructions. virtual unsigned getMemoryOpCost(unsigned Opcode, Type *Src, unsigned Alignment, unsigned AddressSpace) const; /// \brief Calculate the cost of performing a vector reduction. /// /// This is the cost of reducing the vector value of type \p Ty to a scalar /// value using the operation denoted by \p Opcode. The form of the reduction /// can either be a pairwise reduction or a reduction that splits the vector /// at every reduction level. /// /// Pairwise: /// (v0, v1, v2, v3) /// ((v0+v1), (v2, v3), undef, undef) /// Split: /// (v0, v1, v2, v3) /// ((v0+v2), (v1+v3), undef, undef) virtual unsigned getReductionCost(unsigned Opcode, Type *Ty, bool IsPairwiseForm) const; /// \returns The cost of Intrinsic instructions. virtual unsigned getIntrinsicInstrCost(Intrinsic::ID ID, Type *RetTy, ArrayRef<Type *> Tys) const; /// \returns The number of pieces into which the provided type must be /// split during legalization. Zero is returned when the answer is unknown. virtual unsigned getNumberOfParts(Type *Tp) const; /// \returns The cost of the address computation. For most targets this can be /// merged into the instruction indexing mode. Some targets might want to /// distinguish between address computation for memory operations on vector /// types and scalar types. Such targets should override this function. /// The 'IsComplex' parameter is a hint that the address computation is likely /// to involve multiple instructions and as such unlikely to be merged into /// the address indexing mode. virtual unsigned getAddressComputationCost(Type *Ty, bool IsComplex = false) const; /// @} /// Analysis group identification. static char ID; }; /// \brief Create the base case instance of a pass in the TTI analysis group. /// /// This class provides the base case for the stack of TTI analyzes. It doesn't /// delegate to anything and uses the STTI and VTTI objects passed in to /// satisfy the queries. ImmutablePass *createNoTargetTransformInfoPass(); } // End llvm namespace #endif