src/llvm/include/llvm/Analysis/ScalarEvolutionExpander.h

   1 //===---- llvm/Analysis/ScalarEvolutionExpander.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 generate code from scalar expressions.
  11 //
  12 //===----------------------------------------------------------------------===//
  13
  14 #ifndef LLVM_ANALYSIS_SCALAREVOLUTIONEXPANDER_H
  15 #define LLVM_ANALYSIS_SCALAREVOLUTIONEXPANDER_H
  16
  17 #include "llvm/Analysis/ScalarEvolutionExpressions.h"
  18 #include "llvm/Analysis/ScalarEvolutionNormalization.h"
  19 #include "llvm/Analysis/TargetFolder.h"
  20 #include "llvm/IR/IRBuilder.h"
  21 #include "llvm/IR/ValueHandle.h"
  22 #include <set>
  23
  24 namespace llvm {
  25   class TargetTransformInfo;
  26
  27   /// Return true if the given expression is safe to expand in the sense that
  28   /// all materialized values are safe to speculate.
  29   bool isSafeToExpand(const SCEV *S, ScalarEvolution &SE);
  30
  31   /// SCEVExpander - This class uses information about analyze scalars to
  32   /// rewrite expressions in canonical form.
  33   ///
  34   /// Clients should create an instance of this class when rewriting is needed,
  35   /// and destroy it when finished to allow the release of the associated
  36   /// memory.
  37   class SCEVExpander : public SCEVVisitor<SCEVExpander, Value*> {
  38     ScalarEvolution &SE;
  39
  40     // New instructions receive a name to identifies them with the current pass.
  41     const char* IVName;
  42
  43     // InsertedExpressions caches Values for reuse, so must track RAUW.
  44     std::map<std::pair<const SCEV *, Instruction *>, TrackingVH<Value> >
  45       InsertedExpressions;
  46     // InsertedValues only flags inserted instructions so needs no RAUW.
  47     std::set<AssertingVH<Value> > InsertedValues;
  48     std::set<AssertingVH<Value> > InsertedPostIncValues;
  49
  50     /// RelevantLoops - A memoization of the "relevant" loop for a given SCEV.
  51     DenseMap<const SCEV *, const Loop *> RelevantLoops;
  52
  53     /// PostIncLoops - Addrecs referring to any of the given loops are expanded
  54     /// in post-inc mode. For example, expanding {1,+,1}<L> in post-inc mode
  55     /// returns the add instruction that adds one to the phi for {0,+,1}<L>,
  56     /// as opposed to a new phi starting at 1. This is only supported in
  57     /// non-canonical mode.
  58     PostIncLoopSet PostIncLoops;
  59
  60     /// IVIncInsertPos - When this is non-null, addrecs expanded in the
  61     /// loop it indicates should be inserted with increments at
  62     /// IVIncInsertPos.
  63     const Loop *IVIncInsertLoop;
  64
  65     /// IVIncInsertPos - When expanding addrecs in the IVIncInsertLoop loop,
  66     /// insert the IV increment at this position.
  67     Instruction *IVIncInsertPos;
  68
  69     /// Phis that complete an IV chain. Reuse
  70     std::set<AssertingVH<PHINode> > ChainedPhis;
  71
  72     /// CanonicalMode - When true, expressions are expanded in "canonical"
  73     /// form. In particular, addrecs are expanded as arithmetic based on
  74     /// a canonical induction variable. When false, expression are expanded
  75     /// in a more literal form.
  76     bool CanonicalMode;
  77
  78     /// When invoked from LSR, the expander is in "strength reduction" mode. The
  79     /// only difference is that phi's are only reused if they are already in
  80     /// "expanded" form.
  81     bool LSRMode;
  82
  83     typedef IRBuilder<true, TargetFolder> BuilderType;
  84     BuilderType Builder;
  85
  86 #ifndef NDEBUG
  87     const char *DebugType;
  88 #endif
  89
  90     friend struct SCEVVisitor<SCEVExpander, Value*>;
  91
  92   public:
  93     /// SCEVExpander - Construct a SCEVExpander in "canonical" mode.
  94     explicit SCEVExpander(ScalarEvolution &se, const char *name)
  95       : SE(se), IVName(name), IVIncInsertLoop(nullptr), IVIncInsertPos(nullptr),
  96         CanonicalMode(true), LSRMode(false),
  97         Builder(se.getContext(), TargetFolder(se.DL)) {
  98 #ifndef NDEBUG
  99       DebugType = "";
 100 #endif
 101     }
 102
 103 #ifndef NDEBUG
 104     void setDebugType(const char* s) { DebugType = s; }
 105 #endif
 106
 107     /// clear - Erase the contents of the InsertedExpressions map so that users
 108     /// trying to expand the same expression into multiple BasicBlocks or
 109     /// different places within the same BasicBlock can do so.
 110     void clear() {
 111       InsertedExpressions.clear();
 112       InsertedValues.clear();
 113       InsertedPostIncValues.clear();
 114       ChainedPhis.clear();
 115     }
 116
 117     /// getOrInsertCanonicalInductionVariable - This method returns the
 118     /// canonical induction variable of the specified type for the specified
 119     /// loop (inserting one if there is none).  A canonical induction variable
 120     /// starts at zero and steps by one on each iteration.
 121     PHINode *getOrInsertCanonicalInductionVariable(const Loop *L, Type *Ty);
 122
 123     /// getIVIncOperand - Return the induction variable increment's IV operand.
 124     Instruction *getIVIncOperand(Instruction *IncV, Instruction *InsertPos,
 125                                  bool allowScale);
 126
 127     /// hoistIVInc - Utility for hoisting an IV increment.
 128     bool hoistIVInc(Instruction *IncV, Instruction *InsertPos);
 129
 130     /// replaceCongruentIVs - replace congruent phis with their most canonical
 131     /// representative. Return the number of phis eliminated.
 132     unsigned replaceCongruentIVs(Loop *L, const DominatorTree *DT,
 133                                  SmallVectorImpl<WeakVH> &DeadInsts,
 134                                  const TargetTransformInfo *TTI = nullptr);
 135
 136     /// expandCodeFor - Insert code to directly compute the specified SCEV
 137     /// expression into the program.  The inserted code is inserted into the
 138     /// specified block.
 139     Value *expandCodeFor(const SCEV *SH, Type *Ty, Instruction *I);
 140
 141     /// setIVIncInsertPos - Set the current IV increment loop and position.
 142     void setIVIncInsertPos(const Loop *L, Instruction *Pos) {
 143       assert(!CanonicalMode &&
 144              "IV increment positions are not supported in CanonicalMode");
 145       IVIncInsertLoop = L;
 146       IVIncInsertPos = Pos;
 147     }
 148
 149     /// setPostInc - Enable post-inc expansion for addrecs referring to the
 150     /// given loops. Post-inc expansion is only supported in non-canonical
 151     /// mode.
 152     void setPostInc(const PostIncLoopSet &L) {
 153       assert(!CanonicalMode &&
 154              "Post-inc expansion is not supported in CanonicalMode");
 155       PostIncLoops = L;
 156     }
 157
 158     /// clearPostInc - Disable all post-inc expansion.
 159     void clearPostInc() {
 160       PostIncLoops.clear();
 161
 162       // When we change the post-inc loop set, cached expansions may no
 163       // longer be valid.
 164       InsertedPostIncValues.clear();
 165     }
 166
 167     /// disableCanonicalMode - Disable the behavior of expanding expressions in
 168     /// canonical form rather than in a more literal form. Non-canonical mode
 169     /// is useful for late optimization passes.
 170     void disableCanonicalMode() { CanonicalMode = false; }
 171
 172     void enableLSRMode() { LSRMode = true; }
 173
 174     /// clearInsertPoint - Clear the current insertion point. This is useful
 175     /// if the instruction that had been serving as the insertion point may
 176     /// have been deleted.
 177     void clearInsertPoint() {
 178       Builder.ClearInsertionPoint();
 179     }
 180
 181     /// isInsertedInstruction - Return true if the specified instruction was
 182     /// inserted by the code rewriter.  If so, the client should not modify the
 183     /// instruction.
 184     bool isInsertedInstruction(Instruction *I) const {
 185       return InsertedValues.count(I) || InsertedPostIncValues.count(I);
 186     }
 187
 188     void setChainedPhi(PHINode *PN) { ChainedPhis.insert(PN); }
 189
 190   private:
 191     LLVMContext &getContext() const { return SE.getContext(); }
 192
 193     /// InsertBinop - Insert the specified binary operator, doing a small amount
 194     /// of work to avoid inserting an obviously redundant operation.
 195     Value *InsertBinop(Instruction::BinaryOps Opcode, Value *LHS, Value *RHS);
 196
 197     /// ReuseOrCreateCast - Arange for there to be a cast of V to Ty at IP,
 198     /// reusing an existing cast if a suitable one exists, moving an existing
 199     /// cast if a suitable one exists but isn't in the right place, or
 200     /// or creating a new one.
 201     Value *ReuseOrCreateCast(Value *V, Type *Ty,
 202                              Instruction::CastOps Op,
 203                              BasicBlock::iterator IP);
 204
 205     /// InsertNoopCastOfTo - Insert a cast of V to the specified type,
 206     /// which must be possible with a noop cast, doing what we can to
 207     /// share the casts.
 208     Value *InsertNoopCastOfTo(Value *V, Type *Ty);
 209
 210     /// expandAddToGEP - Expand a SCEVAddExpr with a pointer type into a GEP
 211     /// instead of using ptrtoint+arithmetic+inttoptr.
 212     Value *expandAddToGEP(const SCEV *const *op_begin,
 213                           const SCEV *const *op_end,
 214                           PointerType *PTy, Type *Ty, Value *V);
 215
 216     Value *expand(const SCEV *S);
 217
 218     /// expandCodeFor - Insert code to directly compute the specified SCEV
 219     /// expression into the program.  The inserted code is inserted into the
 220     /// SCEVExpander's current insertion point. If a type is specified, the
 221     /// result will be expanded to have that type, with a cast if necessary.
 222     Value *expandCodeFor(const SCEV *SH, Type *Ty = nullptr);
 223
 224     /// getRelevantLoop - Determine the most "relevant" loop for the given SCEV.
 225     const Loop *getRelevantLoop(const SCEV *);
 226
 227     Value *visitConstant(const SCEVConstant *S) {
 228       return S->getValue();
 229     }
 230
 231     Value *visitTruncateExpr(const SCEVTruncateExpr *S);
 232
 233     Value *visitZeroExtendExpr(const SCEVZeroExtendExpr *S);
 234
 235     Value *visitSignExtendExpr(const SCEVSignExtendExpr *S);
 236
 237     Value *visitAddExpr(const SCEVAddExpr *S);
 238
 239     Value *visitMulExpr(const SCEVMulExpr *S);
 240
 241     Value *visitUDivExpr(const SCEVUDivExpr *S);
 242
 243     Value *visitAddRecExpr(const SCEVAddRecExpr *S);
 244
 245     Value *visitSMaxExpr(const SCEVSMaxExpr *S);
 246
 247     Value *visitUMaxExpr(const SCEVUMaxExpr *S);
 248
 249     Value *visitUnknown(const SCEVUnknown *S) {
 250       return S->getValue();
 251     }
 252
 253     void rememberInstruction(Value *I);
 254
 255     bool isNormalAddRecExprPHI(PHINode *PN, Instruction *IncV, const Loop *L);
 256
 257     bool isExpandedAddRecExprPHI(PHINode *PN, Instruction *IncV, const Loop *L);
 258
 259     Value *expandAddRecExprLiterally(const SCEVAddRecExpr *);
 260     PHINode *getAddRecExprPHILiterally(const SCEVAddRecExpr *Normalized,
 261                                        const Loop *L,
 262                                        Type *ExpandTy,
 263                                        Type *IntTy,
 264                                        Type *&TruncTy,
 265                                        bool &InvertStep);
 266     Value *expandIVInc(PHINode *PN, Value *StepV, const Loop *L,
 267                        Type *ExpandTy, Type *IntTy, bool useSubtract);
 268   };
 269 }
 270
 271 #endif