1 //===- llvm/Analysis/TargetTransformInfo.h ----------------------*- C++ -*-===//
3 // The LLVM Compiler Infrastructure
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
8 //===----------------------------------------------------------------------===//
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
15 // 3. Codegen-level implementation which uses target-specific hooks.
17 // This file defines #2, which is the interface that IR-level transformations
18 // use for querying the codegen.
20 //===----------------------------------------------------------------------===//
22 #ifndef LLVM_ANALYSIS_TARGETTRANSFORMINFO_H
23 #define LLVM_ANALYSIS_TARGETTRANSFORMINFO_H
25 #include "llvm/CodeGen/ValueTypes.h"
26 #include "llvm/IR/GlobalValue.h"
27 #include "llvm/IR/Intrinsics.h"
28 #include "llvm/IR/Type.h"
29 #include "llvm/Pass.h"
30 #include "llvm/Support/DataTypes.h"
34 /// TargetTransformInfo - This pass provides access to the codegen
35 /// interfaces that are needed for IR-level transformations.
36 class TargetTransformInfo {
38 /// \brief The TTI instance one level down the stack.
40 /// This is used to implement the default behavior all of the methods which
41 /// is to delegate up through the stack of TTIs until one can answer the
43 TargetTransformInfo *PrevTTI;
45 /// \brief The top of the stack of TTI analyses available.
47 /// This is a convenience routine maintained as TTI analyses become available
48 /// that complements the PrevTTI delegation chain. When one part of an
49 /// analysis pass wants to query another part of the analysis pass it can use
50 /// this to start back at the top of the stack.
51 TargetTransformInfo *TopTTI;
53 /// All pass subclasses must in their initializePass routine call
54 /// pushTTIStack with themselves to update the pointers tracking the previous
55 /// TTI instance in the analysis group's stack, and the top of the analysis
57 void pushTTIStack(Pass *P);
59 /// All pass subclasses must in their finalizePass routine call popTTIStack
60 /// to update the pointers tracking the previous TTI instance in the analysis
61 /// group's stack, and the top of the analysis group's stack.
64 /// All pass subclasses must call TargetTransformInfo::getAnalysisUsage.
65 virtual void getAnalysisUsage(AnalysisUsage &AU) const;
68 /// This class is intended to be subclassed by real implementations.
69 virtual ~TargetTransformInfo() = 0;
71 /// \name Generic Target Information
74 /// \brief Underlying constants for 'cost' values in this interface.
76 /// Many APIs in this interface return a cost. This enum defines the
77 /// fundamental values that should be used to interpret (and produce) those
78 /// costs. The costs are returned as an unsigned rather than a member of this
79 /// enumeration because it is expected that the cost of one IR instruction
80 /// may have a multiplicative factor to it or otherwise won't fit directly
81 /// into the enum. Moreover, it is common to sum or average costs which works
82 /// better as simple integral values. Thus this enum only provides constants.
84 /// Note that these costs should usually reflect the intersection of code-size
85 /// cost and execution cost. A free instruction is typically one that folds
86 /// into another instruction. For example, reg-to-reg moves can often be
87 /// skipped by renaming the registers in the CPU, but they still are encoded
88 /// and thus wouldn't be considered 'free' here.
89 enum TargetCostConstants {
90 TCC_Free = 0, ///< Expected to fold away in lowering.
91 TCC_Basic = 1, ///< The cost of a typical 'add' instruction.
92 TCC_Expensive = 4 ///< The cost of a 'div' instruction on x86.
95 /// \brief Estimate the cost of a specific operation when lowered.
97 /// Note that this is designed to work on an arbitrary synthetic opcode, and
98 /// thus work for hypothetical queries before an instruction has even been
99 /// formed. However, this does *not* work for GEPs, and must not be called
100 /// for a GEP instruction. Instead, use the dedicated getGEPCost interface as
101 /// analyzing a GEP's cost required more information.
103 /// Typically only the result type is required, and the operand type can be
104 /// omitted. However, if the opcode is one of the cast instructions, the
105 /// operand type is required.
107 /// The returned cost is defined in terms of \c TargetCostConstants, see its
108 /// comments for a detailed explanation of the cost values.
109 virtual unsigned getOperationCost(unsigned Opcode, Type *Ty,
110 Type *OpTy = 0) const;
112 /// \brief Estimate the cost of a GEP operation when lowered.
114 /// The contract for this function is the same as \c getOperationCost except
115 /// that it supports an interface that provides extra information specific to
116 /// the GEP operation.
117 virtual unsigned getGEPCost(const Value *Ptr,
118 ArrayRef<const Value *> Operands) const;
120 /// \brief Estimate the cost of a function call when lowered.
122 /// The contract for this is the same as \c getOperationCost except that it
123 /// supports an interface that provides extra information specific to call
126 /// This is the most basic query for estimating call cost: it only knows the
127 /// function type and (potentially) the number of arguments at the call site.
128 /// The latter is only interesting for varargs function types.
129 virtual unsigned getCallCost(FunctionType *FTy, int NumArgs = -1) const;
131 /// \brief Estimate the cost of calling a specific function when lowered.
133 /// This overload adds the ability to reason about the particular function
134 /// being called in the event it is a library call with special lowering.
135 virtual unsigned getCallCost(const Function *F, int NumArgs = -1) const;
137 /// \brief Estimate the cost of calling a specific function when lowered.
139 /// This overload allows specifying a set of candidate argument values.
140 virtual unsigned getCallCost(const Function *F,
141 ArrayRef<const Value *> Arguments) const;
143 /// \brief Estimate the cost of an intrinsic when lowered.
145 /// Mirrors the \c getCallCost method but uses an intrinsic identifier.
146 virtual unsigned getIntrinsicCost(Intrinsic::ID IID, Type *RetTy,
147 ArrayRef<Type *> ParamTys) const;
149 /// \brief Estimate the cost of an intrinsic when lowered.
151 /// Mirrors the \c getCallCost method but uses an intrinsic identifier.
152 virtual unsigned getIntrinsicCost(Intrinsic::ID IID, Type *RetTy,
153 ArrayRef<const Value *> Arguments) const;
155 /// \brief Estimate the cost of a given IR user when lowered.
157 /// This can estimate the cost of either a ConstantExpr or Instruction when
158 /// lowered. It has two primary advantages over the \c getOperationCost and
159 /// \c getGEPCost above, and one significant disadvantage: it can only be
160 /// used when the IR construct has already been formed.
162 /// The advantages are that it can inspect the SSA use graph to reason more
163 /// accurately about the cost. For example, all-constant-GEPs can often be
164 /// folded into a load or other instruction, but if they are used in some
165 /// other context they may not be folded. This routine can distinguish such
168 /// The returned cost is defined in terms of \c TargetCostConstants, see its
169 /// comments for a detailed explanation of the cost values.
170 virtual unsigned getUserCost(const User *U) const;
172 /// \brief Test whether calls to a function lower to actual program function
175 /// The idea is to test whether the program is likely to require a 'call'
176 /// instruction or equivalent in order to call the given function.
178 /// FIXME: It's not clear that this is a good or useful query API. Client's
179 /// should probably move to simpler cost metrics using the above.
180 /// Alternatively, we could split the cost interface into distinct code-size
181 /// and execution-speed costs. This would allow modelling the core of this
182 /// query more accurately as the a call is a single small instruction, but
183 /// incurs significant execution cost.
184 virtual bool isLoweredToCall(const Function *F) const;
188 /// \name Scalar Target Information
191 /// \brief Flags indicating the kind of support for population count.
193 /// Compared to the SW implementation, HW support is supposed to
194 /// significantly boost the performance when the population is dense, and it
195 /// may or may not degrade performance if the population is sparse. A HW
196 /// support is considered as "Fast" if it can outperform, or is on a par
197 /// with, SW implementation when the population is sparse; otherwise, it is
198 /// considered as "Slow".
199 enum PopcntSupportKind {
205 /// isLegalAddImmediate - Return true if the specified immediate is legal
206 /// add immediate, that is the target has add instructions which can add
207 /// a register with the immediate without having to materialize the
208 /// immediate into a register.
209 virtual bool isLegalAddImmediate(int64_t Imm) const;
211 /// isLegalICmpImmediate - Return true if the specified immediate is legal
212 /// icmp immediate, that is the target has icmp instructions which can compare
213 /// a register against the immediate without having to materialize the
214 /// immediate into a register.
215 virtual bool isLegalICmpImmediate(int64_t Imm) const;
217 /// isLegalAddressingMode - Return true if the addressing mode represented by
218 /// AM is legal for this target, for a load/store of the specified type.
219 /// The type may be VoidTy, in which case only return true if the addressing
220 /// mode is legal for a load/store of any legal type.
221 /// TODO: Handle pre/postinc as well.
222 virtual bool isLegalAddressingMode(Type *Ty, GlobalValue *BaseGV,
223 int64_t BaseOffset, bool HasBaseReg,
224 int64_t Scale) const;
226 /// isTruncateFree - Return true if it's free to truncate a value of
227 /// type Ty1 to type Ty2. e.g. On x86 it's free to truncate a i32 value in
228 /// register EAX to i16 by referencing its sub-register AX.
229 virtual bool isTruncateFree(Type *Ty1, Type *Ty2) const;
231 /// Is this type legal.
232 virtual bool isTypeLegal(Type *Ty) const;
234 /// getJumpBufAlignment - returns the target's jmp_buf alignment in bytes
235 virtual unsigned getJumpBufAlignment() const;
237 /// getJumpBufSize - returns the target's jmp_buf size in bytes.
238 virtual unsigned getJumpBufSize() const;
240 /// shouldBuildLookupTables - Return true if switches should be turned into
241 /// lookup tables for the target.
242 virtual bool shouldBuildLookupTables() const;
244 /// getPopcntSupport - Return hardware support for population count.
245 virtual PopcntSupportKind getPopcntSupport(unsigned IntTyWidthInBit) const;
247 /// getIntImmCost - Return the expected cost of materializing the given
248 /// integer immediate of the specified type.
249 virtual unsigned getIntImmCost(const APInt &Imm, Type *Ty) const;
253 /// \name Vector Target Information
256 /// \brief The various kinds of shuffle patterns for vector queries.
258 SK_Broadcast, ///< Broadcast element 0 to all other elements.
259 SK_Reverse, ///< Reverse the order of the vector.
260 SK_InsertSubvector, ///< InsertSubvector. Index indicates start offset.
261 SK_ExtractSubvector ///< ExtractSubvector Index indicates start offset.
264 /// \return The number of scalar or vector registers that the target has.
265 /// If 'Vectors' is true, it returns the number of vector registers. If it is
266 /// set to false, it returns the number of scalar registers.
267 virtual unsigned getNumberOfRegisters(bool Vector) const;
269 /// \return The width of the largest scalar or vector register type.
270 virtual unsigned getRegisterBitWidth(bool Vector) const;
272 /// \return The maximum unroll factor that the vectorizer should try to
273 /// perform for this target. This number depends on the level of parallelism
274 /// and the number of execution units in the CPU.
275 virtual unsigned getMaximumUnrollFactor() const;
277 /// \return The expected cost of arithmetic ops, such as mul, xor, fsub, etc.
278 virtual unsigned getArithmeticInstrCost(unsigned Opcode, Type *Ty) const;
280 /// \return The cost of a shuffle instruction of kind Kind and of type Tp.
281 /// The index and subtype parameters are used by the subvector insertion and
282 /// extraction shuffle kinds.
283 virtual unsigned getShuffleCost(ShuffleKind Kind, Type *Tp, int Index = 0,
284 Type *SubTp = 0) const;
286 /// \return The expected cost of cast instructions, such as bitcast, trunc,
288 virtual unsigned getCastInstrCost(unsigned Opcode, Type *Dst,
291 /// \return The expected cost of control-flow related instructions such as
293 virtual unsigned getCFInstrCost(unsigned Opcode) const;
295 /// \returns The expected cost of compare and select instructions.
296 virtual unsigned getCmpSelInstrCost(unsigned Opcode, Type *ValTy,
297 Type *CondTy = 0) const;
299 /// \return The expected cost of vector Insert and Extract.
300 /// Use -1 to indicate that there is no information on the index value.
301 virtual unsigned getVectorInstrCost(unsigned Opcode, Type *Val,
302 unsigned Index = -1) const;
304 /// \return The cost of Load and Store instructions.
305 virtual unsigned getMemoryOpCost(unsigned Opcode, Type *Src,
307 unsigned AddressSpace) const;
309 /// \returns The cost of Intrinsic instructions.
310 virtual unsigned getIntrinsicInstrCost(Intrinsic::ID ID, Type *RetTy,
311 ArrayRef<Type *> Tys) const;
313 /// \returns The number of pieces into which the provided type must be
314 /// split during legalization. Zero is returned when the answer is unknown.
315 virtual unsigned getNumberOfParts(Type *Tp) const;
317 /// \returns The cost of the address computation. For most targets this can be
318 /// merged into the instruction indexing mode. Some targets might want to
319 /// distinguish between address computation for memory operations on vector
320 /// types and scalar types. Such targets should override this function.
321 virtual unsigned getAddressComputationCost(Type *Ty) const;
325 /// Analysis group identification.
329 /// \brief Create the base case instance of a pass in the TTI analysis group.
331 /// This class provides the base case for the stack of TTI analyzes. It doesn't
332 /// delegate to anything and uses the STTI and VTTI objects passed in to
333 /// satisfy the queries.
334 ImmutablePass *createNoTargetTransformInfoPass();
336 } // End llvm namespace