llvm-6502/include/llvm/Analysis/TargetTransformInfo.h
Andrea Di Biagio 029a76b0a2 [Vectorizer] Add a new 'OperandValueKind' in TargetTransformInfo called
'OK_NonUniformConstValue' to identify operands which are constants but
not constant splats.

The cost model now allows returning 'OK_NonUniformConstValue'
for non splat operands that are instances of ConstantVector or
ConstantDataVector.

With this change, targets are now able to compute different costs
for instructions with non-uniform constant operands.
For example, On X86 the cost of a vector shift may vary depending on whether
the second operand is a uniform or non-uniform constant.

This patch applies the following changes:
 - The cost model computation now takes into account non-uniform constants;
 - The cost of vector shift instructions has been improved in
   X86TargetTransformInfo analysis pass;
 - BBVectorize, SLPVectorizer and LoopVectorize now know how to distinguish
   between non-uniform and uniform constant operands.

Added a new test to verify that the output of opt
'-cost-model -analyze' is valid in the following configurations: SSE2,
SSE4.1, AVX, AVX2.



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@201272 91177308-0d34-0410-b5e6-96231b3b80d8
2014-02-12 23:43:47 +00:00

427 lines
19 KiB
C++

//===- 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_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 Opcode, const APInt &Imm,
Type *Ty) const;
virtual unsigned getIntImmCost(Intrinsic::ID IID, 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