include/llvm/Analysis/ScalarEvolutionExpressions.h

   1 //===- llvm/Analysis/ScalarEvolutionExpressions.h - SCEV Exprs --*- 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 file defines the classes used to represent and build scalar expressions.
  11 //
  12 //===----------------------------------------------------------------------===//
  13
  14 #ifndef LLVM_ANALYSIS_SCALAREVOLUTIONEXPRESSIONS_H
  15 #define LLVM_ANALYSIS_SCALAREVOLUTIONEXPRESSIONS_H
  16
  17 #include "llvm/ADT/DenseMap.h"
  18 #include "llvm/ADT/FoldingSet.h"
  19 #include "llvm/ADT/SmallPtrSet.h"
  20 #include "llvm/ADT/SmallVector.h"
  21 #include "llvm/ADT/iterator_range.h"
  22 #include "llvm/Analysis/ScalarEvolution.h"
  23 #include "llvm/IR/Constants.h"
  24 #include "llvm/IR/Value.h"
  25 #include "llvm/IR/ValueHandle.h"
  26 #include "llvm/Support/Casting.h"
  27 #include "llvm/Support/ErrorHandling.h"
  28 #include <cassert>
  29 #include <cstddef>
  30
  31 namespace llvm {
  32
  33 class APInt;
  34 class Constant;
  35 class ConstantRange;
  36 class Loop;
  37 class Type;
  38
  39   enum SCEVTypes {
  40     // These should be ordered in terms of increasing complexity to make the
  41     // folders simpler.
  42     scConstant, scTruncate, scZeroExtend, scSignExtend, scAddExpr, scMulExpr,
  43     scUDivExpr, scAddRecExpr, scUMaxExpr, scSMaxExpr,
  44     scUnknown, scCouldNotCompute
  45   };
  46
  47   /// This class represents a constant integer value.
  48   class SCEVConstant : public SCEV {
  49     friend class ScalarEvolution;
  50
  51     ConstantInt *V;
  52
  53     SCEVConstant(const FoldingSetNodeIDRef ID, ConstantInt *v) :
  54       SCEV(ID, scConstant), V(v) {}
  55
  56   public:
  57     ConstantInt *getValue() const { return V; }
  58     const APInt &getAPInt() const { return getValue()->getValue(); }
  59
  60     Type *getType() const { return V->getType(); }
  61
  62     /// Methods for support type inquiry through isa, cast, and dyn_cast:
  63     static bool classof(const SCEV *S) {
  64       return S->getSCEVType() == scConstant;
  65     }
  66   };
  67
  68   /// This is the base class for unary cast operator classes.
  69   class SCEVCastExpr : public SCEV {
  70   protected:
  71     const SCEV *Op;
  72     Type *Ty;
  73
  74     SCEVCastExpr(const FoldingSetNodeIDRef ID,
  75                  unsigned SCEVTy, const SCEV *op, Type *ty);
  76
  77   public:
  78     const SCEV *getOperand() const { return Op; }
  79     Type *getType() const { return Ty; }
  80
  81     /// Methods for support type inquiry through isa, cast, and dyn_cast:
  82     static bool classof(const SCEV *S) {
  83       return S->getSCEVType() == scTruncate ||
  84              S->getSCEVType() == scZeroExtend ||
  85              S->getSCEVType() == scSignExtend;
  86     }
  87   };
  88
  89   /// This class represents a truncation of an integer value to a
  90   /// smaller integer value.
  91   class SCEVTruncateExpr : public SCEVCastExpr {
  92     friend class ScalarEvolution;
  93
  94     SCEVTruncateExpr(const FoldingSetNodeIDRef ID,
  95                      const SCEV *op, Type *ty);
  96
  97   public:
  98     /// Methods for support type inquiry through isa, cast, and dyn_cast:
  99     static bool classof(const SCEV *S) {
 100       return S->getSCEVType() == scTruncate;
 101     }
 102   };
 103
 104   /// This class represents a zero extension of a small integer value
 105   /// to a larger integer value.
 106   class SCEVZeroExtendExpr : public SCEVCastExpr {
 107     friend class ScalarEvolution;
 108
 109     SCEVZeroExtendExpr(const FoldingSetNodeIDRef ID,
 110                        const SCEV *op, Type *ty);
 111
 112   public:
 113     /// Methods for support type inquiry through isa, cast, and dyn_cast:
 114     static bool classof(const SCEV *S) {
 115       return S->getSCEVType() == scZeroExtend;
 116     }
 117   };
 118
 119   /// This class represents a sign extension of a small integer value
 120   /// to a larger integer value.
 121   class SCEVSignExtendExpr : public SCEVCastExpr {
 122     friend class ScalarEvolution;
 123
 124     SCEVSignExtendExpr(const FoldingSetNodeIDRef ID,
 125                        const SCEV *op, Type *ty);
 126
 127   public:
 128     /// Methods for support type inquiry through isa, cast, and dyn_cast:
 129     static bool classof(const SCEV *S) {
 130       return S->getSCEVType() == scSignExtend;
 131     }
 132   };
 133
 134   /// This node is a base class providing common functionality for
 135   /// n'ary operators.
 136   class SCEVNAryExpr : public SCEV {
 137   protected:
 138     // Since SCEVs are immutable, ScalarEvolution allocates operand
 139     // arrays with its SCEVAllocator, so this class just needs a simple
 140     // pointer rather than a more elaborate vector-like data structure.
 141     // This also avoids the need for a non-trivial destructor.
 142     const SCEV *const *Operands;
 143     size_t NumOperands;
 144
 145     SCEVNAryExpr(const FoldingSetNodeIDRef ID,
 146                  enum SCEVTypes T, const SCEV *const *O, size_t N)
 147       : SCEV(ID, T), Operands(O), NumOperands(N) {}
 148
 149   public:
 150     size_t getNumOperands() const { return NumOperands; }
 151
 152     const SCEV *getOperand(unsigned i) const {
 153       assert(i < NumOperands && "Operand index out of range!");
 154       return Operands[i];
 155     }
 156
 157     using op_iterator = const SCEV *const *;
 158     using op_range = iterator_range<op_iterator>;
 159
 160     op_iterator op_begin() const { return Operands; }
 161     op_iterator op_end() const { return Operands + NumOperands; }
 162     op_range operands() const {
 163       return make_range(op_begin(), op_end());
 164     }
 165
 166     Type *getType() const { return getOperand(0)->getType(); }
 167
 168     NoWrapFlags getNoWrapFlags(NoWrapFlags Mask = NoWrapMask) const {
 169       return (NoWrapFlags)(SubclassData & Mask);
 170     }
 171
 172     bool hasNoUnsignedWrap() const {
 173       return getNoWrapFlags(FlagNUW) != FlagAnyWrap;
 174     }
 175
 176     bool hasNoSignedWrap() const {
 177       return getNoWrapFlags(FlagNSW) != FlagAnyWrap;
 178     }
 179
 180     bool hasNoSelfWrap() const {
 181       return getNoWrapFlags(FlagNW) != FlagAnyWrap;
 182     }
 183
 184     /// Methods for support type inquiry through isa, cast, and dyn_cast:
 185     static bool classof(const SCEV *S) {
 186       return S->getSCEVType() == scAddExpr ||
 187              S->getSCEVType() == scMulExpr ||
 188              S->getSCEVType() == scSMaxExpr ||
 189              S->getSCEVType() == scUMaxExpr ||
 190              S->getSCEVType() == scAddRecExpr;
 191     }
 192   };
 193
 194   /// This node is the base class for n'ary commutative operators.
 195   class SCEVCommutativeExpr : public SCEVNAryExpr {
 196   protected:
 197     SCEVCommutativeExpr(const FoldingSetNodeIDRef ID,
 198                         enum SCEVTypes T, const SCEV *const *O, size_t N)
 199       : SCEVNAryExpr(ID, T, O, N) {}
 200
 201   public:
 202     /// Methods for support type inquiry through isa, cast, and dyn_cast:
 203     static bool classof(const SCEV *S) {
 204       return S->getSCEVType() == scAddExpr ||
 205              S->getSCEVType() == scMulExpr ||
 206              S->getSCEVType() == scSMaxExpr ||
 207              S->getSCEVType() == scUMaxExpr;
 208     }
 209
 210     /// Set flags for a non-recurrence without clearing previously set flags.
 211     void setNoWrapFlags(NoWrapFlags Flags) {
 212       SubclassData |= Flags;
 213     }
 214   };
 215
 216   /// This node represents an addition of some number of SCEVs.
 217   class SCEVAddExpr : public SCEVCommutativeExpr {
 218     friend class ScalarEvolution;
 219
 220     SCEVAddExpr(const FoldingSetNodeIDRef ID,
 221                 const SCEV *const *O, size_t N)
 222       : SCEVCommutativeExpr(ID, scAddExpr, O, N) {}
 223
 224   public:
 225     Type *getType() const {
 226       // Use the type of the last operand, which is likely to be a pointer
 227       // type, if there is one. This doesn't usually matter, but it can help
 228       // reduce casts when the expressions are expanded.
 229       return getOperand(getNumOperands() - 1)->getType();
 230     }
 231
 232     /// Methods for support type inquiry through isa, cast, and dyn_cast:
 233     static bool classof(const SCEV *S) {
 234       return S->getSCEVType() == scAddExpr;
 235     }
 236   };
 237
 238   /// This node represents multiplication of some number of SCEVs.
 239   class SCEVMulExpr : public SCEVCommutativeExpr {
 240     friend class ScalarEvolution;
 241
 242     SCEVMulExpr(const FoldingSetNodeIDRef ID,
 243                 const SCEV *const *O, size_t N)
 244       : SCEVCommutativeExpr(ID, scMulExpr, O, N) {}
 245
 246   public:
 247     /// Methods for support type inquiry through isa, cast, and dyn_cast:
 248     static bool classof(const SCEV *S) {
 249       return S->getSCEVType() == scMulExpr;
 250     }
 251   };
 252
 253   /// This class represents a binary unsigned division operation.
 254   class SCEVUDivExpr : public SCEV {
 255     friend class ScalarEvolution;
 256
 257     const SCEV *LHS;
 258     const SCEV *RHS;
 259
 260     SCEVUDivExpr(const FoldingSetNodeIDRef ID, const SCEV *lhs, const SCEV *rhs)
 261       : SCEV(ID, scUDivExpr), LHS(lhs), RHS(rhs) {}
 262
 263   public:
 264     const SCEV *getLHS() const { return LHS; }
 265     const SCEV *getRHS() const { return RHS; }
 266
 267     Type *getType() const {
 268       // In most cases the types of LHS and RHS will be the same, but in some
 269       // crazy cases one or the other may be a pointer. ScalarEvolution doesn't
 270       // depend on the type for correctness, but handling types carefully can
 271       // avoid extra casts in the SCEVExpander. The LHS is more likely to be
 272       // a pointer type than the RHS, so use the RHS' type here.
 273       return getRHS()->getType();
 274     }
 275
 276     /// Methods for support type inquiry through isa, cast, and dyn_cast:
 277     static bool classof(const SCEV *S) {
 278       return S->getSCEVType() == scUDivExpr;
 279     }
 280   };
 281
 282   /// This node represents a polynomial recurrence on the trip count
 283   /// of the specified loop.  This is the primary focus of the
 284   /// ScalarEvolution framework; all the other SCEV subclasses are
 285   /// mostly just supporting infrastructure to allow SCEVAddRecExpr
 286   /// expressions to be created and analyzed.
 287   ///
 288   /// All operands of an AddRec are required to be loop invariant.
 289   ///
 290   class SCEVAddRecExpr : public SCEVNAryExpr {
 291     friend class ScalarEvolution;
 292
 293     const Loop *L;
 294
 295     SCEVAddRecExpr(const FoldingSetNodeIDRef ID,
 296                    const SCEV *const *O, size_t N, const Loop *l)
 297       : SCEVNAryExpr(ID, scAddRecExpr, O, N), L(l) {}
 298
 299   public:
 300     const SCEV *getStart() const { return Operands[0]; }
 301     const Loop *getLoop() const { return L; }
 302
 303     /// Constructs and returns the recurrence indicating how much this
 304     /// expression steps by.  If this is a polynomial of degree N, it
 305     /// returns a chrec of degree N-1.  We cannot determine whether
 306     /// the step recurrence has self-wraparound.
 307     const SCEV *getStepRecurrence(ScalarEvolution &SE) const {
 308       if (isAffine()) return getOperand(1);
 309       return SE.getAddRecExpr(SmallVector<const SCEV *, 3>(op_begin()+1,
 310                                                            op_end()),
 311                               getLoop(), FlagAnyWrap);
 312     }
 313
 314     /// Return true if this represents an expression A + B*x where A
 315     /// and B are loop invariant values.
 316     bool isAffine() const {
 317       // We know that the start value is invariant.  This expression is thus
 318       // affine iff the step is also invariant.
 319       return getNumOperands() == 2;
 320     }
 321
 322     /// Return true if this represents an expression A + B*x + C*x^2
 323     /// where A, B and C are loop invariant values.  This corresponds
 324     /// to an addrec of the form {L,+,M,+,N}
 325     bool isQuadratic() const {
 326       return getNumOperands() == 3;
 327     }
 328
 329     /// Set flags for a recurrence without clearing any previously set flags.
 330     /// For AddRec, either NUW or NSW implies NW. Keep track of this fact here
 331     /// to make it easier to propagate flags.
 332     void setNoWrapFlags(NoWrapFlags Flags) {
 333       if (Flags & (FlagNUW | FlagNSW))
 334         Flags = ScalarEvolution::setFlags(Flags, FlagNW);
 335       SubclassData |= Flags;
 336     }
 337
 338     /// Return the value of this chain of recurrences at the specified
 339     /// iteration number.
 340     const SCEV *evaluateAtIteration(const SCEV *It, ScalarEvolution &SE) const;
 341
 342     /// Return the number of iterations of this loop that produce
 343     /// values in the specified constant range.  Another way of
 344     /// looking at this is that it returns the first iteration number
 345     /// where the value is not in the condition, thus computing the
 346     /// exit count.  If the iteration count can't be computed, an
 347     /// instance of SCEVCouldNotCompute is returned.
 348     const SCEV *getNumIterationsInRange(const ConstantRange &Range,
 349                                         ScalarEvolution &SE) const;
 350
 351     /// Return an expression representing the value of this expression
 352     /// one iteration of the loop ahead.
 353     const SCEVAddRecExpr *getPostIncExpr(ScalarEvolution &SE) const;
 354
 355     /// Methods for support type inquiry through isa, cast, and dyn_cast:
 356     static bool classof(const SCEV *S) {
 357       return S->getSCEVType() == scAddRecExpr;
 358     }
 359   };
 360
 361   /// This class represents a signed maximum selection.
 362   class SCEVSMaxExpr : public SCEVCommutativeExpr {
 363     friend class ScalarEvolution;
 364
 365     SCEVSMaxExpr(const FoldingSetNodeIDRef ID,
 366                  const SCEV *const *O, size_t N)
 367       : SCEVCommutativeExpr(ID, scSMaxExpr, O, N) {
 368       // Max never overflows.
 369       setNoWrapFlags((NoWrapFlags)(FlagNUW | FlagNSW));
 370     }
 371
 372   public:
 373     /// Methods for support type inquiry through isa, cast, and dyn_cast:
 374     static bool classof(const SCEV *S) {
 375       return S->getSCEVType() == scSMaxExpr;
 376     }
 377   };
 378
 379   /// This class represents an unsigned maximum selection.
 380   class SCEVUMaxExpr : public SCEVCommutativeExpr {
 381     friend class ScalarEvolution;
 382
 383     SCEVUMaxExpr(const FoldingSetNodeIDRef ID,
 384                  const SCEV *const *O, size_t N)
 385       : SCEVCommutativeExpr(ID, scUMaxExpr, O, N) {
 386       // Max never overflows.
 387       setNoWrapFlags((NoWrapFlags)(FlagNUW | FlagNSW));
 388     }
 389
 390   public:
 391     /// Methods for support type inquiry through isa, cast, and dyn_cast:
 392     static bool classof(const SCEV *S) {
 393       return S->getSCEVType() == scUMaxExpr;
 394     }
 395   };
 396
 397   /// This means that we are dealing with an entirely unknown SCEV
 398   /// value, and only represent it as its LLVM Value.  This is the
 399   /// "bottom" value for the analysis.
 400   class SCEVUnknown final : public SCEV, private CallbackVH {
 401     friend class ScalarEvolution;
 402
 403     /// The parent ScalarEvolution value. This is used to update the
 404     /// parent's maps when the value associated with a SCEVUnknown is
 405     /// deleted or RAUW'd.
 406     ScalarEvolution *SE;
 407
 408     /// The next pointer in the linked list of all SCEVUnknown
 409     /// instances owned by a ScalarEvolution.
 410     SCEVUnknown *Next;
 411
 412     SCEVUnknown(const FoldingSetNodeIDRef ID, Value *V,
 413                 ScalarEvolution *se, SCEVUnknown *next) :
 414       SCEV(ID, scUnknown), CallbackVH(V), SE(se), Next(next) {}
 415
 416     // Implement CallbackVH.
 417     void deleted() override;
 418     void allUsesReplacedWith(Value *New) override;
 419
 420   public:
 421     Value *getValue() const { return getValPtr(); }
 422
 423     /// @{
 424     /// Test whether this is a special constant representing a type
 425     /// size, alignment, or field offset in a target-independent
 426     /// manner, and hasn't happened to have been folded with other
 427     /// operations into something unrecognizable. This is mainly only
 428     /// useful for pretty-printing and other situations where it isn't
 429     /// absolutely required for these to succeed.
 430     bool isSizeOf(Type *&AllocTy) const;
 431     bool isAlignOf(Type *&AllocTy) const;
 432     bool isOffsetOf(Type *&STy, Constant *&FieldNo) const;
 433     /// @}
 434
 435     Type *getType() const { return getValPtr()->getType(); }
 436
 437     /// Methods for support type inquiry through isa, cast, and dyn_cast:
 438     static bool classof(const SCEV *S) {
 439       return S->getSCEVType() == scUnknown;
 440     }
 441   };
 442
 443   /// This class defines a simple visitor class that may be used for
 444   /// various SCEV analysis purposes.
 445   template<typename SC, typename RetVal=void>
 446   struct SCEVVisitor {
 447     RetVal visit(const SCEV *S) {
 448       switch (S->getSCEVType()) {
 449       case scConstant:
 450         return ((SC*)this)->visitConstant((const SCEVConstant*)S);
 451       case scTruncate:
 452         return ((SC*)this)->visitTruncateExpr((const SCEVTruncateExpr*)S);
 453       case scZeroExtend:
 454         return ((SC*)this)->visitZeroExtendExpr((const SCEVZeroExtendExpr*)S);
 455       case scSignExtend:
 456         return ((SC*)this)->visitSignExtendExpr((const SCEVSignExtendExpr*)S);
 457       case scAddExpr:
 458         return ((SC*)this)->visitAddExpr((const SCEVAddExpr*)S);
 459       case scMulExpr:
 460         return ((SC*)this)->visitMulExpr((const SCEVMulExpr*)S);
 461       case scUDivExpr:
 462         return ((SC*)this)->visitUDivExpr((const SCEVUDivExpr*)S);
 463       case scAddRecExpr:
 464         return ((SC*)this)->visitAddRecExpr((const SCEVAddRecExpr*)S);
 465       case scSMaxExpr:
 466         return ((SC*)this)->visitSMaxExpr((const SCEVSMaxExpr*)S);
 467       case scUMaxExpr:
 468         return ((SC*)this)->visitUMaxExpr((const SCEVUMaxExpr*)S);
 469       case scUnknown:
 470         return ((SC*)this)->visitUnknown((const SCEVUnknown*)S);
 471       case scCouldNotCompute:
 472         return ((SC*)this)->visitCouldNotCompute((const SCEVCouldNotCompute*)S);
 473       default:
 474         llvm_unreachable("Unknown SCEV type!");
 475       }
 476     }
 477
 478     RetVal visitCouldNotCompute(const SCEVCouldNotCompute *S) {
 479       llvm_unreachable("Invalid use of SCEVCouldNotCompute!");
 480     }
 481   };
 482
 483   /// Visit all nodes in the expression tree using worklist traversal.
 484   ///
 485   /// Visitor implements:
 486   ///   // return true to follow this node.
 487   ///   bool follow(const SCEV *S);
 488   ///   // return true to terminate the search.
 489   ///   bool isDone();
 490   template<typename SV>
 491   class SCEVTraversal {
 492     SV &Visitor;
 493     SmallVector<const SCEV *, 8> Worklist;
 494     SmallPtrSet<const SCEV *, 8> Visited;
 495
 496     void push(const SCEV *S) {
 497       if (Visited.insert(S).second && Visitor.follow(S))
 498         Worklist.push_back(S);
 499     }
 500
 501   public:
 502     SCEVTraversal(SV& V): Visitor(V) {}
 503
 504     void visitAll(const SCEV *Root) {
 505       push(Root);
 506       while (!Worklist.empty() && !Visitor.isDone()) {
 507         const SCEV *S = Worklist.pop_back_val();
 508
 509         switch (S->getSCEVType()) {
 510         case scConstant:
 511         case scUnknown:
 512           break;
 513         case scTruncate:
 514         case scZeroExtend:
 515         case scSignExtend:
 516           push(cast<SCEVCastExpr>(S)->getOperand());
 517           break;
 518         case scAddExpr:
 519         case scMulExpr:
 520         case scSMaxExpr:
 521         case scUMaxExpr:
 522         case scAddRecExpr:
 523           for (const auto *Op : cast<SCEVNAryExpr>(S)->operands())
 524             push(Op);
 525           break;
 526         case scUDivExpr: {
 527           const SCEVUDivExpr *UDiv = cast<SCEVUDivExpr>(S);
 528           push(UDiv->getLHS());
 529           push(UDiv->getRHS());
 530           break;
 531         }
 532         case scCouldNotCompute:
 533           llvm_unreachable("Attempt to use a SCEVCouldNotCompute object!");
 534         default:
 535           llvm_unreachable("Unknown SCEV kind!");
 536         }
 537       }
 538     }
 539   };
 540
 541   /// Use SCEVTraversal to visit all nodes in the given expression tree.
 542   template<typename SV>
 543   void visitAll(const SCEV *Root, SV& Visitor) {
 544     SCEVTraversal<SV> T(Visitor);
 545     T.visitAll(Root);
 546   }
 547
 548   /// Return true if any node in \p Root satisfies the predicate \p Pred.
 549   template <typename PredTy>
 550   bool SCEVExprContains(const SCEV *Root, PredTy Pred) {
 551     struct FindClosure {
 552       bool Found = false;
 553       PredTy Pred;
 554
 555       FindClosure(PredTy Pred) : Pred(Pred) {}
 556
 557       bool follow(const SCEV *S) {
 558         if (!Pred(S))
 559           return true;
 560
 561         Found = true;
 562         return false;
 563       }
 564
 565       bool isDone() const { return Found; }
 566     };
 567
 568     FindClosure FC(Pred);
 569     visitAll(Root, FC);
 570     return FC.Found;
 571   }
 572
 573   /// This visitor recursively visits a SCEV expression and re-writes it.
 574   /// The result from each visit is cached, so it will return the same
 575   /// SCEV for the same input.
 576   template<typename SC>
 577   class SCEVRewriteVisitor : public SCEVVisitor<SC, const SCEV *> {
 578   protected:
 579     ScalarEvolution &SE;
 580     // Memoize the result of each visit so that we only compute once for
 581     // the same input SCEV. This is to avoid redundant computations when
 582     // a SCEV is referenced by multiple SCEVs. Without memoization, this
 583     // visit algorithm would have exponential time complexity in the worst
 584     // case, causing the compiler to hang on certain tests.
 585     DenseMap<const SCEV *, const SCEV *> RewriteResults;
 586
 587   public:
 588     SCEVRewriteVisitor(ScalarEvolution &SE) : SE(SE) {}
 589
 590     const SCEV *visit(const SCEV *S) {
 591       auto It = RewriteResults.find(S);
 592       if (It != RewriteResults.end())
 593         return It->second;
 594       auto* Visited = SCEVVisitor<SC, const SCEV *>::visit(S);
 595       auto Result = RewriteResults.try_emplace(S, Visited);
 596       assert(Result.second && "Should insert a new entry");
 597       return Result.first->second;
 598     }
 599
 600     const SCEV *visitConstant(const SCEVConstant *Constant) {
 601       return Constant;
 602     }
 603
 604     const SCEV *visitTruncateExpr(const SCEVTruncateExpr *Expr) {
 605       const SCEV *Operand = ((SC*)this)->visit(Expr->getOperand());
 606       return Operand == Expr->getOperand()
 607                  ? Expr
 608                  : SE.getTruncateExpr(Operand, Expr->getType());
 609     }
 610
 611     const SCEV *visitZeroExtendExpr(const SCEVZeroExtendExpr *Expr) {
 612       const SCEV *Operand = ((SC*)this)->visit(Expr->getOperand());
 613       return Operand == Expr->getOperand()
 614                  ? Expr
 615                  : SE.getZeroExtendExpr(Operand, Expr->getType());
 616     }
 617
 618     const SCEV *visitSignExtendExpr(const SCEVSignExtendExpr *Expr) {
 619       const SCEV *Operand = ((SC*)this)->visit(Expr->getOperand());
 620       return Operand == Expr->getOperand()
 621                  ? Expr
 622                  : SE.getSignExtendExpr(Operand, Expr->getType());
 623     }
 624
 625     const SCEV *visitAddExpr(const SCEVAddExpr *Expr) {
 626       SmallVector<const SCEV *, 2> Operands;
 627       bool Changed = false;
 628       for (auto *Op : Expr->operands()) {
 629         Operands.push_back(((SC*)this)->visit(Op));
 630         Changed |= Op != Operands.back();
 631       }
 632       return !Changed ? Expr : SE.getAddExpr(Operands);
 633     }
 634
 635     const SCEV *visitMulExpr(const SCEVMulExpr *Expr) {
 636       SmallVector<const SCEV *, 2> Operands;
 637       bool Changed = false;
 638       for (auto *Op : Expr->operands()) {
 639         Operands.push_back(((SC*)this)->visit(Op));
 640         Changed |= Op != Operands.back();
 641       }
 642       return !Changed ? Expr : SE.getMulExpr(Operands);
 643     }
 644
 645     const SCEV *visitUDivExpr(const SCEVUDivExpr *Expr) {
 646       auto *LHS = ((SC *)this)->visit(Expr->getLHS());
 647       auto *RHS = ((SC *)this)->visit(Expr->getRHS());
 648       bool Changed = LHS != Expr->getLHS() || RHS != Expr->getRHS();
 649       return !Changed ? Expr : SE.getUDivExpr(LHS, RHS);
 650     }
 651
 652     const SCEV *visitAddRecExpr(const SCEVAddRecExpr *Expr) {
 653       SmallVector<const SCEV *, 2> Operands;
 654       bool Changed = false;
 655       for (auto *Op : Expr->operands()) {
 656         Operands.push_back(((SC*)this)->visit(Op));
 657         Changed |= Op != Operands.back();
 658       }
 659       return !Changed ? Expr
 660                       : SE.getAddRecExpr(Operands, Expr->getLoop(),
 661                                          Expr->getNoWrapFlags());
 662     }
 663
 664     const SCEV *visitSMaxExpr(const SCEVSMaxExpr *Expr) {
 665       SmallVector<const SCEV *, 2> Operands;
 666       bool Changed = false;
 667       for (auto *Op : Expr->operands()) {
 668         Operands.push_back(((SC *)this)->visit(Op));
 669         Changed |= Op != Operands.back();
 670       }
 671       return !Changed ? Expr : SE.getSMaxExpr(Operands);
 672     }
 673
 674     const SCEV *visitUMaxExpr(const SCEVUMaxExpr *Expr) {
 675       SmallVector<const SCEV *, 2> Operands;
 676       bool Changed = false;
 677       for (auto *Op : Expr->operands()) {
 678         Operands.push_back(((SC*)this)->visit(Op));
 679         Changed |= Op != Operands.back();
 680       }
 681       return !Changed ? Expr : SE.getUMaxExpr(Operands);
 682     }
 683
 684     const SCEV *visitUnknown(const SCEVUnknown *Expr) {
 685       return Expr;
 686     }
 687
 688     const SCEV *visitCouldNotCompute(const SCEVCouldNotCompute *Expr) {
 689       return Expr;
 690     }
 691   };
 692
 693   using ValueToValueMap = DenseMap<const Value *, Value *>;
 694
 695   /// The SCEVParameterRewriter takes a scalar evolution expression and updates
 696   /// the SCEVUnknown components following the Map (Value -> Value).
 697   class SCEVParameterRewriter : public SCEVRewriteVisitor<SCEVParameterRewriter> {
 698   public:
 699     static const SCEV *rewrite(const SCEV *Scev, ScalarEvolution &SE,
 700                                ValueToValueMap &Map,
 701                                bool InterpretConsts = false) {
 702       SCEVParameterRewriter Rewriter(SE, Map, InterpretConsts);
 703       return Rewriter.visit(Scev);
 704     }
 705
 706     SCEVParameterRewriter(ScalarEvolution &SE, ValueToValueMap &M, bool C)
 707       : SCEVRewriteVisitor(SE), Map(M), InterpretConsts(C) {}
 708
 709     const SCEV *visitUnknown(const SCEVUnknown *Expr) {
 710       Value *V = Expr->getValue();
 711       if (Map.count(V)) {
 712         Value *NV = Map[V];
 713         if (InterpretConsts && isa<ConstantInt>(NV))
 714           return SE.getConstant(cast<ConstantInt>(NV));
 715         return SE.getUnknown(NV);
 716       }
 717       return Expr;
 718     }
 719
 720   private:
 721     ValueToValueMap &Map;
 722     bool InterpretConsts;
 723   };
 724
 725   using LoopToScevMapT = DenseMap<const Loop *, const SCEV *>;
 726
 727   /// The SCEVLoopAddRecRewriter takes a scalar evolution expression and applies
 728   /// the Map (Loop -> SCEV) to all AddRecExprs.
 729   class SCEVLoopAddRecRewriter
 730       : public SCEVRewriteVisitor<SCEVLoopAddRecRewriter> {
 731   public:
 732     SCEVLoopAddRecRewriter(ScalarEvolution &SE, LoopToScevMapT &M)
 733         : SCEVRewriteVisitor(SE), Map(M) {}
 734
 735     static const SCEV *rewrite(const SCEV *Scev, LoopToScevMapT &Map,
 736                                ScalarEvolution &SE) {
 737       SCEVLoopAddRecRewriter Rewriter(SE, Map);
 738       return Rewriter.visit(Scev);
 739     }
 740
 741     const SCEV *visitAddRecExpr(const SCEVAddRecExpr *Expr) {
 742       SmallVector<const SCEV *, 2> Operands;
 743       for (const SCEV *Op : Expr->operands())
 744         Operands.push_back(visit(Op));
 745
 746       const Loop *L = Expr->getLoop();
 747       const SCEV *Res = SE.getAddRecExpr(Operands, L, Expr->getNoWrapFlags());
 748
 749       if (0 == Map.count(L))
 750         return Res;
 751
 752       const SCEVAddRecExpr *Rec = cast<SCEVAddRecExpr>(Res);
 753       return Rec->evaluateAtIteration(Map[L], SE);
 754     }
 755
 756   private:
 757     LoopToScevMapT &Map;
 758   };
 759
 760 } // end namespace llvm
 761
 762 #endif // LLVM_ANALYSIS_SCALAREVOLUTIONEXPRESSIONS_H