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