TargetTransformInfo.h revision 135fe6ac5f5b80ef68c19b3ec7bb0063e28f2bab
1//===- llvm/Analysis/TargetTransformInfo.h ----------------------*- C++ -*-===// 2// 3// The LLVM Compiler Infrastructure 4// 5// This file is distributed under the University of Illinois Open Source 6// License. See LICENSE.TXT for details. 7// 8//===----------------------------------------------------------------------===// 9// 10// This pass exposes codegen information to IR-level passes. Every 11// transformation that uses codegen information is broken into three parts: 12// 1. The IR-level analysis pass. 13// 2. The IR-level transformation interface which provides the needed 14// information. 15// 3. Codegen-level implementation which uses target-specific hooks. 16// 17// This file defines #2, which is the interface that IR-level transformations 18// use for querying the codegen. 19// 20//===----------------------------------------------------------------------===// 21 22#ifndef LLVM_ANALYSIS_TARGETTRANSFORMINFO_H 23#define LLVM_ANALYSIS_TARGETTRANSFORMINFO_H 24 25#include "llvm/IR/Intrinsics.h" 26#include "llvm/Pass.h" 27#include "llvm/Support/DataTypes.h" 28 29namespace llvm { 30 31class GlobalValue; 32class Loop; 33class Type; 34class User; 35class Value; 36 37/// TargetTransformInfo - This pass provides access to the codegen 38/// interfaces that are needed for IR-level transformations. 39class TargetTransformInfo { 40protected: 41 /// \brief The TTI instance one level down the stack. 42 /// 43 /// This is used to implement the default behavior all of the methods which 44 /// is to delegate up through the stack of TTIs until one can answer the 45 /// query. 46 TargetTransformInfo *PrevTTI; 47 48 /// \brief The top of the stack of TTI analyses available. 49 /// 50 /// This is a convenience routine maintained as TTI analyses become available 51 /// that complements the PrevTTI delegation chain. When one part of an 52 /// analysis pass wants to query another part of the analysis pass it can use 53 /// this to start back at the top of the stack. 54 TargetTransformInfo *TopTTI; 55 56 /// All pass subclasses must in their initializePass routine call 57 /// pushTTIStack with themselves to update the pointers tracking the previous 58 /// TTI instance in the analysis group's stack, and the top of the analysis 59 /// group's stack. 60 void pushTTIStack(Pass *P); 61 62 /// All pass subclasses must in their finalizePass routine call popTTIStack 63 /// to update the pointers tracking the previous TTI instance in the analysis 64 /// group's stack, and the top of the analysis group's stack. 65 void popTTIStack(); 66 67 /// All pass subclasses must call TargetTransformInfo::getAnalysisUsage. 68 virtual void getAnalysisUsage(AnalysisUsage &AU) const; 69 70public: 71 /// This class is intended to be subclassed by real implementations. 72 virtual ~TargetTransformInfo() = 0; 73 74 /// \name Generic Target Information 75 /// @{ 76 77 /// \brief Underlying constants for 'cost' values in this interface. 78 /// 79 /// Many APIs in this interface return a cost. This enum defines the 80 /// fundamental values that should be used to interpret (and produce) those 81 /// costs. The costs are returned as an unsigned rather than a member of this 82 /// enumeration because it is expected that the cost of one IR instruction 83 /// may have a multiplicative factor to it or otherwise won't fit directly 84 /// into the enum. Moreover, it is common to sum or average costs which works 85 /// better as simple integral values. Thus this enum only provides constants. 86 /// 87 /// Note that these costs should usually reflect the intersection of code-size 88 /// cost and execution cost. A free instruction is typically one that folds 89 /// into another instruction. For example, reg-to-reg moves can often be 90 /// skipped by renaming the registers in the CPU, but they still are encoded 91 /// and thus wouldn't be considered 'free' here. 92 enum TargetCostConstants { 93 TCC_Free = 0, ///< Expected to fold away in lowering. 94 TCC_Basic = 1, ///< The cost of a typical 'add' instruction. 95 TCC_Expensive = 4 ///< The cost of a 'div' instruction on x86. 96 }; 97 98 /// \brief Estimate the cost of a specific operation when lowered. 99 /// 100 /// Note that this is designed to work on an arbitrary synthetic opcode, and 101 /// thus work for hypothetical queries before an instruction has even been 102 /// formed. However, this does *not* work for GEPs, and must not be called 103 /// for a GEP instruction. Instead, use the dedicated getGEPCost interface as 104 /// analyzing a GEP's cost required more information. 105 /// 106 /// Typically only the result type is required, and the operand type can be 107 /// omitted. However, if the opcode is one of the cast instructions, the 108 /// operand type is required. 109 /// 110 /// The returned cost is defined in terms of \c TargetCostConstants, see its 111 /// comments for a detailed explanation of the cost values. 112 virtual unsigned getOperationCost(unsigned Opcode, Type *Ty, 113 Type *OpTy = 0) const; 114 115 /// \brief Estimate the cost of a GEP operation when lowered. 116 /// 117 /// The contract for this function is the same as \c getOperationCost except 118 /// that it supports an interface that provides extra information specific to 119 /// the GEP operation. 120 virtual unsigned getGEPCost(const Value *Ptr, 121 ArrayRef<const Value *> Operands) const; 122 123 /// \brief Estimate the cost of a function call when lowered. 124 /// 125 /// The contract for this is the same as \c getOperationCost except that it 126 /// supports an interface that provides extra information specific to call 127 /// instructions. 128 /// 129 /// This is the most basic query for estimating call cost: it only knows the 130 /// function type and (potentially) the number of arguments at the call site. 131 /// The latter is only interesting for varargs function types. 132 virtual unsigned getCallCost(FunctionType *FTy, int NumArgs = -1) const; 133 134 /// \brief Estimate the cost of calling a specific function when lowered. 135 /// 136 /// This overload adds the ability to reason about the particular function 137 /// being called in the event it is a library call with special lowering. 138 virtual unsigned getCallCost(const Function *F, int NumArgs = -1) const; 139 140 /// \brief Estimate the cost of calling a specific function when lowered. 141 /// 142 /// This overload allows specifying a set of candidate argument values. 143 virtual unsigned getCallCost(const Function *F, 144 ArrayRef<const Value *> Arguments) const; 145 146 /// \brief Estimate the cost of an intrinsic when lowered. 147 /// 148 /// Mirrors the \c getCallCost method but uses an intrinsic identifier. 149 virtual unsigned getIntrinsicCost(Intrinsic::ID IID, Type *RetTy, 150 ArrayRef<Type *> ParamTys) const; 151 152 /// \brief Estimate the cost of an intrinsic when lowered. 153 /// 154 /// Mirrors the \c getCallCost method but uses an intrinsic identifier. 155 virtual unsigned getIntrinsicCost(Intrinsic::ID IID, Type *RetTy, 156 ArrayRef<const Value *> Arguments) const; 157 158 /// \brief Estimate the cost of a given IR user when lowered. 159 /// 160 /// This can estimate the cost of either a ConstantExpr or Instruction when 161 /// lowered. It has two primary advantages over the \c getOperationCost and 162 /// \c getGEPCost above, and one significant disadvantage: it can only be 163 /// used when the IR construct has already been formed. 164 /// 165 /// The advantages are that it can inspect the SSA use graph to reason more 166 /// accurately about the cost. For example, all-constant-GEPs can often be 167 /// folded into a load or other instruction, but if they are used in some 168 /// other context they may not be folded. This routine can distinguish such 169 /// cases. 170 /// 171 /// The returned cost is defined in terms of \c TargetCostConstants, see its 172 /// comments for a detailed explanation of the cost values. 173 virtual unsigned getUserCost(const User *U) const; 174 175 /// \brief hasBranchDivergence - Return true if branch divergence exists. 176 /// Branch divergence has a significantly negative impact on GPU performance 177 /// when threads in the same wavefront take different paths due to conditional 178 /// branches. 179 virtual bool hasBranchDivergence() const; 180 181 /// \brief Test whether calls to a function lower to actual program function 182 /// calls. 183 /// 184 /// The idea is to test whether the program is likely to require a 'call' 185 /// instruction or equivalent in order to call the given function. 186 /// 187 /// FIXME: It's not clear that this is a good or useful query API. Client's 188 /// should probably move to simpler cost metrics using the above. 189 /// Alternatively, we could split the cost interface into distinct code-size 190 /// and execution-speed costs. This would allow modelling the core of this 191 /// query more accurately as the a call is a single small instruction, but 192 /// incurs significant execution cost. 193 virtual bool isLoweredToCall(const Function *F) const; 194 195 /// Parameters that control the generic loop unrolling transformation. 196 struct UnrollingPreferences { 197 /// The cost threshold for the unrolled loop, compared to 198 /// CodeMetrics.NumInsts aggregated over all basic blocks in the loop body. 199 /// The unrolling factor is set such that the unrolled loop body does not 200 /// exceed this cost. Set this to UINT_MAX to disable the loop body cost 201 /// restriction. 202 unsigned Threshold; 203 /// The cost threshold for the unrolled loop when optimizing for size (set 204 /// to UINT_MAX to disable). 205 unsigned OptSizeThreshold; 206 /// A forced unrolling factor (the number of concatenated bodies of the 207 /// original loop in the unrolled loop body). When set to 0, the unrolling 208 /// transformation will select an unrolling factor based on the current cost 209 /// threshold and other factors. 210 unsigned Count; 211 /// Allow partial unrolling (unrolling of loops to expand the size of the 212 /// loop body, not only to eliminate small constant-trip-count loops). 213 bool Partial; 214 /// Allow runtime unrolling (unrolling of loops to expand the size of the 215 /// loop body even when the number of loop iterations is not known at compile 216 /// time). 217 bool Runtime; 218 }; 219 220 /// \brief Get target-customized preferences for the generic loop unrolling 221 /// transformation. The caller will initialize UP with the current 222 /// target-independent defaults. 223 virtual void getUnrollingPreferences(Loop *L, UnrollingPreferences &UP) const; 224 225 /// @} 226 227 /// \name Scalar Target Information 228 /// @{ 229 230 /// \brief Flags indicating the kind of support for population count. 231 /// 232 /// Compared to the SW implementation, HW support is supposed to 233 /// significantly boost the performance when the population is dense, and it 234 /// may or may not degrade performance if the population is sparse. A HW 235 /// support is considered as "Fast" if it can outperform, or is on a par 236 /// with, SW implementation when the population is sparse; otherwise, it is 237 /// considered as "Slow". 238 enum PopcntSupportKind { 239 PSK_Software, 240 PSK_SlowHardware, 241 PSK_FastHardware 242 }; 243 244 /// isLegalAddImmediate - Return true if the specified immediate is legal 245 /// add immediate, that is the target has add instructions which can add 246 /// a register with the immediate without having to materialize the 247 /// immediate into a register. 248 virtual bool isLegalAddImmediate(int64_t Imm) const; 249 250 /// isLegalICmpImmediate - Return true if the specified immediate is legal 251 /// icmp immediate, that is the target has icmp instructions which can compare 252 /// a register against the immediate without having to materialize the 253 /// immediate into a register. 254 virtual bool isLegalICmpImmediate(int64_t Imm) const; 255 256 /// isLegalAddressingMode - Return true if the addressing mode represented by 257 /// AM is legal for this target, for a load/store of the specified type. 258 /// The type may be VoidTy, in which case only return true if the addressing 259 /// mode is legal for a load/store of any legal type. 260 /// TODO: Handle pre/postinc as well. 261 virtual bool isLegalAddressingMode(Type *Ty, GlobalValue *BaseGV, 262 int64_t BaseOffset, bool HasBaseReg, 263 int64_t Scale) const; 264 265 /// \brief Return the cost of the scaling factor used in the addressing 266 /// mode represented by AM for this target, for a load/store 267 /// of the specified type. 268 /// If the AM is supported, the return value must be >= 0. 269 /// If the AM is not supported, it returns a negative value. 270 /// TODO: Handle pre/postinc as well. 271 virtual int getScalingFactorCost(Type *Ty, GlobalValue *BaseGV, 272 int64_t BaseOffset, bool HasBaseReg, 273 int64_t Scale) const; 274 275 /// isTruncateFree - Return true if it's free to truncate a value of 276 /// type Ty1 to type Ty2. e.g. On x86 it's free to truncate a i32 value in 277 /// register EAX to i16 by referencing its sub-register AX. 278 virtual bool isTruncateFree(Type *Ty1, Type *Ty2) const; 279 280 /// Is this type legal. 281 virtual bool isTypeLegal(Type *Ty) const; 282 283 /// getJumpBufAlignment - returns the target's jmp_buf alignment in bytes 284 virtual unsigned getJumpBufAlignment() const; 285 286 /// getJumpBufSize - returns the target's jmp_buf size in bytes. 287 virtual unsigned getJumpBufSize() const; 288 289 /// shouldBuildLookupTables - Return true if switches should be turned into 290 /// lookup tables for the target. 291 virtual bool shouldBuildLookupTables() const; 292 293 /// getPopcntSupport - Return hardware support for population count. 294 virtual PopcntSupportKind getPopcntSupport(unsigned IntTyWidthInBit) const; 295 296 /// haveFastSqrt -- Return true if the hardware has a fast square-root 297 /// instruction. 298 virtual bool haveFastSqrt(Type *Ty) const; 299 300 /// getIntImmCost - Return the expected cost of materializing the given 301 /// integer immediate of the specified type. 302 virtual unsigned getIntImmCost(const APInt &Imm, Type *Ty) const; 303 304 /// @} 305 306 /// \name Vector Target Information 307 /// @{ 308 309 /// \brief The various kinds of shuffle patterns for vector queries. 310 enum ShuffleKind { 311 SK_Broadcast, ///< Broadcast element 0 to all other elements. 312 SK_Reverse, ///< Reverse the order of the vector. 313 SK_InsertSubvector, ///< InsertSubvector. Index indicates start offset. 314 SK_ExtractSubvector ///< ExtractSubvector Index indicates start offset. 315 }; 316 317 /// \brief Additional information about an operand's possible values. 318 enum OperandValueKind { 319 OK_AnyValue, // Operand can have any value. 320 OK_UniformValue, // Operand is uniform (splat of a value). 321 OK_UniformConstantValue // Operand is uniform constant. 322 }; 323 324 /// \return The number of scalar or vector registers that the target has. 325 /// If 'Vectors' is true, it returns the number of vector registers. If it is 326 /// set to false, it returns the number of scalar registers. 327 virtual unsigned getNumberOfRegisters(bool Vector) const; 328 329 /// \return The width of the largest scalar or vector register type. 330 virtual unsigned getRegisterBitWidth(bool Vector) const; 331 332 /// \return The maximum unroll factor that the vectorizer should try to 333 /// perform for this target. This number depends on the level of parallelism 334 /// and the number of execution units in the CPU. 335 virtual unsigned getMaximumUnrollFactor() const; 336 337 /// \return The expected cost of arithmetic ops, such as mul, xor, fsub, etc. 338 virtual unsigned getArithmeticInstrCost(unsigned Opcode, Type *Ty, 339 OperandValueKind Opd1Info = OK_AnyValue, 340 OperandValueKind Opd2Info = OK_AnyValue) const; 341 342 /// \return The cost of a shuffle instruction of kind Kind and of type Tp. 343 /// The index and subtype parameters are used by the subvector insertion and 344 /// extraction shuffle kinds. 345 virtual unsigned getShuffleCost(ShuffleKind Kind, Type *Tp, int Index = 0, 346 Type *SubTp = 0) const; 347 348 /// \return The expected cost of cast instructions, such as bitcast, trunc, 349 /// zext, etc. 350 virtual unsigned getCastInstrCost(unsigned Opcode, Type *Dst, 351 Type *Src) const; 352 353 /// \return The expected cost of control-flow related instructions such as 354 /// Phi, Ret, Br. 355 virtual unsigned getCFInstrCost(unsigned Opcode) const; 356 357 /// \returns The expected cost of compare and select instructions. 358 virtual unsigned getCmpSelInstrCost(unsigned Opcode, Type *ValTy, 359 Type *CondTy = 0) const; 360 361 /// \return The expected cost of vector Insert and Extract. 362 /// Use -1 to indicate that there is no information on the index value. 363 virtual unsigned getVectorInstrCost(unsigned Opcode, Type *Val, 364 unsigned Index = -1) const; 365 366 /// \return The cost of Load and Store instructions. 367 virtual unsigned getMemoryOpCost(unsigned Opcode, Type *Src, 368 unsigned Alignment, 369 unsigned AddressSpace) const; 370 371 /// \brief Calculate the cost of performing a vector reduction. 372 /// 373 /// This is the cost of reducing the vector value of type \p Ty to a scalar 374 /// value using the operation denoted by \p Opcode. The form of the reduction 375 /// can either be a pairwise reduction or a reduction that splits the vector 376 /// at every reduction level. 377 /// 378 /// Pairwise: 379 /// (v0, v1, v2, v3) 380 /// ((v0+v1), (v2, v3), undef, undef) 381 /// Split: 382 /// (v0, v1, v2, v3) 383 /// ((v0+v2), (v1+v3), undef, undef) 384 virtual unsigned getReductionCost(unsigned Opcode, Type *Ty, 385 bool IsPairwiseForm) const; 386 387 /// \returns The cost of Intrinsic instructions. 388 virtual unsigned getIntrinsicInstrCost(Intrinsic::ID ID, Type *RetTy, 389 ArrayRef<Type *> Tys) const; 390 391 /// \returns The number of pieces into which the provided type must be 392 /// split during legalization. Zero is returned when the answer is unknown. 393 virtual unsigned getNumberOfParts(Type *Tp) const; 394 395 /// \returns The cost of the address computation. For most targets this can be 396 /// merged into the instruction indexing mode. Some targets might want to 397 /// distinguish between address computation for memory operations on vector 398 /// types and scalar types. Such targets should override this function. 399 /// The 'IsComplex' parameter is a hint that the address computation is likely 400 /// to involve multiple instructions and as such unlikely to be merged into 401 /// the address indexing mode. 402 virtual unsigned getAddressComputationCost(Type *Ty, 403 bool IsComplex = false) const; 404 405 /// @} 406 407 /// Analysis group identification. 408 static char ID; 409}; 410 411/// \brief Create the base case instance of a pass in the TTI analysis group. 412/// 413/// This class provides the base case for the stack of TTI analyzes. It doesn't 414/// delegate to anything and uses the STTI and VTTI objects passed in to 415/// satisfy the queries. 416ImmutablePass *createNoTargetTransformInfoPass(); 417 418} // End llvm namespace 419 420#endif 421