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/IR/IRBuilder.h" 20 #include "llvm/Support/TargetFolder.h" 21 #include "llvm/Support/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); 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(0), IVIncInsertPos(0), 96 CanonicalMode(true), LSRMode(false), 97 Builder(se.getContext(), TargetFolder(se.TD)) { 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 = NULL); 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 = 0); 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 void restoreInsertPoint(BasicBlock *BB, BasicBlock::iterator I); 256 257 bool isNormalAddRecExprPHI(PHINode *PN, Instruction *IncV, const Loop *L); 258 259 bool isExpandedAddRecExprPHI(PHINode *PN, Instruction *IncV, const Loop *L); 260 261 Value *expandAddRecExprLiterally(const SCEVAddRecExpr *); 262 PHINode *getAddRecExprPHILiterally(const SCEVAddRecExpr *Normalized, 263 const Loop *L, 264 Type *ExpandTy, 265 Type *IntTy); 266 Value *expandIVInc(PHINode *PN, Value *StepV, const Loop *L, 267 Type *ExpandTy, Type *IntTy, bool useSubtract); 268 }; 269 } 270 271 #endif 272
