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