ScalarEvolution.h revision 2d1be87ee40a4a0241d94448173879d9df2bc5b3
1//===- llvm/Analysis/ScalarEvolution.h - Scalar Evolution -------*- 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// The ScalarEvolution class is an LLVM pass which can be used to analyze and 11// catagorize scalar expressions in loops. It specializes in recognizing 12// general induction variables, representing them with the abstract and opaque 13// SCEV class. Given this analysis, trip counts of loops and other important 14// properties can be obtained. 15// 16// This analysis is primarily useful for induction variable substitution and 17// strength reduction. 18// 19//===----------------------------------------------------------------------===// 20 21#ifndef LLVM_ANALYSIS_SCALAREVOLUTION_H 22#define LLVM_ANALYSIS_SCALAREVOLUTION_H 23 24#include "llvm/Pass.h" 25#include "llvm/Analysis/LoopInfo.h" 26#include "llvm/Support/DataTypes.h" 27#include <iosfwd> 28 29namespace llvm { 30 class APInt; 31 class ConstantInt; 32 class Type; 33 class SCEVHandle; 34 class ScalarEvolution; 35 class TargetData; 36 37 /// SCEV - This class represent an analyzed expression in the program. These 38 /// are reference counted opaque objects that the client is not allowed to 39 /// do much with directly. 40 /// 41 class SCEV { 42 const unsigned SCEVType; // The SCEV baseclass this node corresponds to 43 mutable unsigned RefCount; 44 45 friend class SCEVHandle; 46 void addRef() const { ++RefCount; } 47 void dropRef() const { 48 if (--RefCount == 0) 49 delete this; 50 } 51 52 SCEV(const SCEV &); // DO NOT IMPLEMENT 53 void operator=(const SCEV &); // DO NOT IMPLEMENT 54 protected: 55 virtual ~SCEV(); 56 public: 57 explicit SCEV(unsigned SCEVTy) : SCEVType(SCEVTy), RefCount(0) {} 58 59 unsigned getSCEVType() const { return SCEVType; } 60 61 /// isLoopInvariant - Return true if the value of this SCEV is unchanging in 62 /// the specified loop. 63 virtual bool isLoopInvariant(const Loop *L) const = 0; 64 65 /// hasComputableLoopEvolution - Return true if this SCEV changes value in a 66 /// known way in the specified loop. This property being true implies that 67 /// the value is variant in the loop AND that we can emit an expression to 68 /// compute the value of the expression at any particular loop iteration. 69 virtual bool hasComputableLoopEvolution(const Loop *L) const = 0; 70 71 /// getType - Return the LLVM type of this SCEV expression. 72 /// 73 virtual const Type *getType() const = 0; 74 75 /// isZero - Return true if the expression is a constant zero. 76 /// 77 bool isZero() const; 78 79 /// replaceSymbolicValuesWithConcrete - If this SCEV internally references 80 /// the symbolic value "Sym", construct and return a new SCEV that produces 81 /// the same value, but which uses the concrete value Conc instead of the 82 /// symbolic value. If this SCEV does not use the symbolic value, it 83 /// returns itself. 84 virtual SCEVHandle 85 replaceSymbolicValuesWithConcrete(const SCEVHandle &Sym, 86 const SCEVHandle &Conc, 87 ScalarEvolution &SE) const = 0; 88 89 /// dominates - Return true if elements that makes up this SCEV dominates 90 /// the specified basic block. 91 virtual bool dominates(BasicBlock *BB, DominatorTree *DT) const = 0; 92 93 /// print - Print out the internal representation of this scalar to the 94 /// specified stream. This should really only be used for debugging 95 /// purposes. 96 virtual void print(std::ostream &OS) const = 0; 97 void print(std::ostream *OS) const { if (OS) print(*OS); } 98 99 /// dump - This method is used for debugging. 100 /// 101 void dump() const; 102 }; 103 104 inline std::ostream &operator<<(std::ostream &OS, const SCEV &S) { 105 S.print(OS); 106 return OS; 107 } 108 109 /// SCEVCouldNotCompute - An object of this class is returned by queries that 110 /// could not be answered. For example, if you ask for the number of 111 /// iterations of a linked-list traversal loop, you will get one of these. 112 /// None of the standard SCEV operations are valid on this class, it is just a 113 /// marker. 114 struct SCEVCouldNotCompute : public SCEV { 115 SCEVCouldNotCompute(); 116 117 // None of these methods are valid for this object. 118 virtual bool isLoopInvariant(const Loop *L) const; 119 virtual const Type *getType() const; 120 virtual bool hasComputableLoopEvolution(const Loop *L) const; 121 virtual void print(std::ostream &OS) const; 122 void print(std::ostream *OS) const { if (OS) print(*OS); } 123 virtual SCEVHandle 124 replaceSymbolicValuesWithConcrete(const SCEVHandle &Sym, 125 const SCEVHandle &Conc, 126 ScalarEvolution &SE) const; 127 128 virtual bool dominates(BasicBlock *BB, DominatorTree *DT) const { 129 return true; 130 } 131 132 /// Methods for support type inquiry through isa, cast, and dyn_cast: 133 static inline bool classof(const SCEVCouldNotCompute *S) { return true; } 134 static bool classof(const SCEV *S); 135 }; 136 137 /// SCEVHandle - This class is used to maintain the SCEV object's refcounts, 138 /// freeing the objects when the last reference is dropped. 139 class SCEVHandle { 140 SCEV *S; 141 SCEVHandle(); // DO NOT IMPLEMENT 142 public: 143 SCEVHandle(const SCEV *s) : S(const_cast<SCEV*>(s)) { 144 assert(S && "Cannot create a handle to a null SCEV!"); 145 S->addRef(); 146 } 147 SCEVHandle(const SCEVHandle &RHS) : S(RHS.S) { 148 S->addRef(); 149 } 150 ~SCEVHandle() { S->dropRef(); } 151 152 operator SCEV*() const { return S; } 153 154 SCEV &operator*() const { return *S; } 155 SCEV *operator->() const { return S; } 156 157 bool operator==(SCEV *RHS) const { return S == RHS; } 158 bool operator!=(SCEV *RHS) const { return S != RHS; } 159 160 const SCEVHandle &operator=(SCEV *RHS) { 161 if (S != RHS) { 162 S->dropRef(); 163 S = RHS; 164 S->addRef(); 165 } 166 return *this; 167 } 168 169 const SCEVHandle &operator=(const SCEVHandle &RHS) { 170 if (S != RHS.S) { 171 S->dropRef(); 172 S = RHS.S; 173 S->addRef(); 174 } 175 return *this; 176 } 177 }; 178 179 template<typename From> struct simplify_type; 180 template<> struct simplify_type<const SCEVHandle> { 181 typedef SCEV* SimpleType; 182 static SimpleType getSimplifiedValue(const SCEVHandle &Node) { 183 return Node; 184 } 185 }; 186 template<> struct simplify_type<SCEVHandle> 187 : public simplify_type<const SCEVHandle> {}; 188 189 /// ScalarEvolution - This class is the main scalar evolution driver. Because 190 /// client code (intentionally) can't do much with the SCEV objects directly, 191 /// they must ask this class for services. 192 /// 193 class ScalarEvolution : public FunctionPass { 194 void *Impl; // ScalarEvolution uses the pimpl pattern 195 public: 196 static char ID; // Pass identification, replacement for typeid 197 ScalarEvolution() : FunctionPass(&ID), Impl(0) {} 198 199 // getTargetData - Return the TargetData object contained in this 200 // ScalarEvolution. 201 const TargetData &getTargetData() const; 202 203 /// getSCEV - Return a SCEV expression handle for the full generality of the 204 /// specified expression. 205 SCEVHandle getSCEV(Value *V) const; 206 207 SCEVHandle getConstant(ConstantInt *V); 208 SCEVHandle getConstant(const APInt& Val); 209 SCEVHandle getTruncateExpr(const SCEVHandle &Op, const Type *Ty); 210 SCEVHandle getZeroExtendExpr(const SCEVHandle &Op, const Type *Ty); 211 SCEVHandle getSignExtendExpr(const SCEVHandle &Op, const Type *Ty); 212 SCEVHandle getAddExpr(std::vector<SCEVHandle> &Ops); 213 SCEVHandle getAddExpr(const SCEVHandle &LHS, const SCEVHandle &RHS) { 214 std::vector<SCEVHandle> Ops; 215 Ops.push_back(LHS); 216 Ops.push_back(RHS); 217 return getAddExpr(Ops); 218 } 219 SCEVHandle getAddExpr(const SCEVHandle &Op0, const SCEVHandle &Op1, 220 const SCEVHandle &Op2) { 221 std::vector<SCEVHandle> Ops; 222 Ops.push_back(Op0); 223 Ops.push_back(Op1); 224 Ops.push_back(Op2); 225 return getAddExpr(Ops); 226 } 227 SCEVHandle getMulExpr(std::vector<SCEVHandle> &Ops); 228 SCEVHandle getMulExpr(const SCEVHandle &LHS, const SCEVHandle &RHS) { 229 std::vector<SCEVHandle> Ops; 230 Ops.push_back(LHS); 231 Ops.push_back(RHS); 232 return getMulExpr(Ops); 233 } 234 SCEVHandle getUDivExpr(const SCEVHandle &LHS, const SCEVHandle &RHS); 235 SCEVHandle getAddRecExpr(const SCEVHandle &Start, const SCEVHandle &Step, 236 const Loop *L); 237 SCEVHandle getAddRecExpr(std::vector<SCEVHandle> &Operands, 238 const Loop *L); 239 SCEVHandle getAddRecExpr(const std::vector<SCEVHandle> &Operands, 240 const Loop *L) { 241 std::vector<SCEVHandle> NewOp(Operands); 242 return getAddRecExpr(NewOp, L); 243 } 244 SCEVHandle getSMaxExpr(const SCEVHandle &LHS, const SCEVHandle &RHS); 245 SCEVHandle getSMaxExpr(std::vector<SCEVHandle> Operands); 246 SCEVHandle getUMaxExpr(const SCEVHandle &LHS, const SCEVHandle &RHS); 247 SCEVHandle getUMaxExpr(std::vector<SCEVHandle> Operands); 248 SCEVHandle getUnknown(Value *V); 249 250 /// getNegativeSCEV - Return the SCEV object corresponding to -V. 251 /// 252 SCEVHandle getNegativeSCEV(const SCEVHandle &V); 253 254 /// getNotSCEV - Return the SCEV object corresponding to ~V. 255 /// 256 SCEVHandle getNotSCEV(const SCEVHandle &V); 257 258 /// getMinusSCEV - Return LHS-RHS. 259 /// 260 SCEVHandle getMinusSCEV(const SCEVHandle &LHS, 261 const SCEVHandle &RHS); 262 263 /// getTruncateOrZeroExtend - Return a SCEV corresponding to a conversion 264 /// of the input value to the specified type. If the type must be 265 /// extended, it is zero extended. 266 SCEVHandle getTruncateOrZeroExtend(const SCEVHandle &V, const Type *Ty); 267 268 /// getTruncateOrSignExtend - Return a SCEV corresponding to a conversion 269 /// of the input value to the specified type. If the type must be 270 /// extended, it is sign extended. 271 SCEVHandle getTruncateOrSignExtend(const SCEVHandle &V, const Type *Ty); 272 273 /// getIntegerSCEV - Given an integer or FP type, create a constant for the 274 /// specified signed integer value and return a SCEV for the constant. 275 SCEVHandle getIntegerSCEV(int Val, const Type *Ty); 276 277 /// hasSCEV - Return true if the SCEV for this value has already been 278 /// computed. 279 bool hasSCEV(Value *V) const; 280 281 /// setSCEV - Insert the specified SCEV into the map of current SCEVs for 282 /// the specified value. 283 void setSCEV(Value *V, const SCEVHandle &H); 284 285 /// getSCEVAtScope - Return a SCEV expression handle for the specified value 286 /// at the specified scope in the program. The L value specifies a loop 287 /// nest to evaluate the expression at, where null is the top-level or a 288 /// specified loop is immediately inside of the loop. 289 /// 290 /// This method can be used to compute the exit value for a variable defined 291 /// in a loop by querying what the value will hold in the parent loop. 292 /// 293 /// If this value is not computable at this scope, a SCEVCouldNotCompute 294 /// object is returned. 295 SCEVHandle getSCEVAtScope(Value *V, const Loop *L) const; 296 297 /// isLoopGuardedByCond - Test whether entry to the loop is protected by 298 /// a conditional between LHS and RHS. 299 bool isLoopGuardedByCond(const Loop *L, ICmpInst::Predicate Pred, 300 SCEV *LHS, SCEV *RHS); 301 302 /// getBackedgeTakenCount - If the specified loop has a predictable 303 /// backedge-taken count, return it, otherwise return a SCEVCouldNotCompute 304 /// object. The backedge-taken count is the number of times the loop header 305 /// will be branched to from within the loop. This is one less than the 306 /// trip count of the loop, since it doesn't count the first iteration, 307 /// when the header is branched to from outside the loop. 308 /// 309 /// Note that it is not valid to call this method on a loop without a 310 /// loop-invariant backedge-taken count (see 311 /// hasLoopInvariantBackedgeTakenCount). 312 /// 313 SCEVHandle getBackedgeTakenCount(const Loop *L) const; 314 315 /// hasLoopInvariantBackedgeTakenCount - Return true if the specified loop 316 /// has an analyzable loop-invariant backedge-taken count. 317 bool hasLoopInvariantBackedgeTakenCount(const Loop *L) const; 318 319 /// forgetLoopBackedgeTakenCount - This method should be called by the 320 /// client when it has changed a loop in a way that may effect 321 /// ScalarEvolution's ability to compute a trip count, or if the loop 322 /// is deleted. 323 void forgetLoopBackedgeTakenCount(const Loop *L); 324 325 /// deleteValueFromRecords - This method should be called by the 326 /// client before it removes a Value from the program, to make sure 327 /// that no dangling references are left around. 328 void deleteValueFromRecords(Value *V) const; 329 330 virtual bool runOnFunction(Function &F); 331 virtual void releaseMemory(); 332 virtual void getAnalysisUsage(AnalysisUsage &AU) const; 333 virtual void print(std::ostream &OS, const Module* = 0) const; 334 void print(std::ostream *OS, const Module* M = 0) const { 335 if (OS) print(*OS, M); 336 } 337 }; 338} 339 340#endif 341