darwin-x86_64/include/llvm/Analysis/TargetTransformInfo.h - platform/prebuilts/android-emulator-build/mesa-deps - Git at Google

 //===- 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 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_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 = nullptr) 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;
     /// The cost threshold for the unrolled loop, like Threshold, but used
     /// for partial/runtime unrolling (set to UINT_MAX to disable).
     unsigned PartialThreshold;
     /// The cost threshold for the unrolled loop when optimizing for size, like
     /// OptSizeThreshold, but used for partial/runtime unrolling (set to UINT_MAX
     /// to disable).
     unsigned PartialOptSizeThreshold;
     /// 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;
     // Set the maximum unrolling factor. The unrolling factor may be selected
     // using the appropriate cost threshold, but may not exceed this number
     // (set to UINT_MAX to disable). This does not apply in cases where the
     // loop is being fully unrolled.
     unsigned MaxCount;
     /// 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_Alternate,       ///< Choose alternate elements from 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 = nullptr) 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 = nullptr) 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
	//===- 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 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_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 = nullptr) 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;
	/// The cost threshold for the unrolled loop, like Threshold, but used
	/// for partial/runtime unrolling (set to UINT_MAX to disable).
	unsigned PartialThreshold;
	/// The cost threshold for the unrolled loop when optimizing for size, like
	/// OptSizeThreshold, but used for partial/runtime unrolling (set to UINT_MAX
	/// to disable).
	unsigned PartialOptSizeThreshold;
	/// 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;
	// Set the maximum unrolling factor. The unrolling factor may be selected
	// using the appropriate cost threshold, but may not exceed this number
	// (set to UINT_MAX to disable). This does not apply in cases where the
	// loop is being fully unrolled.
	unsigned MaxCount;
	/// 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_Alternate, ///< Choose alternate elements from 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 = nullptr) 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 = nullptr) 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