ScalarEvolutionExpander.h revision 64925c55c65f9345a69fb67db07aa62cfb723577
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 24namespace 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 /// hoistStep - Utility for hoisting an IV increment. 118 static bool hoistStep(Instruction *IncV, Instruction *InsertPos, 119 const DominatorTree *DT); 120 121 /// replaceCongruentIVs - replace congruent phis with their most canonical 122 /// representative. Return the number of phis eliminated. 123 unsigned replaceCongruentIVs(Loop *L, const DominatorTree *DT, 124 SmallVectorImpl<WeakVH> &DeadInsts, 125 const TargetLowering *TLI = NULL); 126 127 /// expandCodeFor - Insert code to directly compute the specified SCEV 128 /// expression into the program. The inserted code is inserted into the 129 /// specified block. 130 Value *expandCodeFor(const SCEV *SH, Type *Ty, Instruction *I); 131 132 /// setIVIncInsertPos - Set the current IV increment loop and position. 133 void setIVIncInsertPos(const Loop *L, Instruction *Pos) { 134 assert(!CanonicalMode && 135 "IV increment positions are not supported in CanonicalMode"); 136 IVIncInsertLoop = L; 137 IVIncInsertPos = Pos; 138 } 139 140 /// setPostInc - Enable post-inc expansion for addrecs referring to the 141 /// given loops. Post-inc expansion is only supported in non-canonical 142 /// mode. 143 void setPostInc(const PostIncLoopSet &L) { 144 assert(!CanonicalMode && 145 "Post-inc expansion is not supported in CanonicalMode"); 146 PostIncLoops = L; 147 } 148 149 /// clearPostInc - Disable all post-inc expansion. 150 void clearPostInc() { 151 PostIncLoops.clear(); 152 153 // When we change the post-inc loop set, cached expansions may no 154 // longer be valid. 155 InsertedPostIncValues.clear(); 156 } 157 158 /// disableCanonicalMode - Disable the behavior of expanding expressions in 159 /// canonical form rather than in a more literal form. Non-canonical mode 160 /// is useful for late optimization passes. 161 void disableCanonicalMode() { CanonicalMode = false; } 162 163 void enableLSRMode() { LSRMode = true; } 164 165 /// clearInsertPoint - Clear the current insertion point. This is useful 166 /// if the instruction that had been serving as the insertion point may 167 /// have been deleted. 168 void clearInsertPoint() { 169 Builder.ClearInsertionPoint(); 170 } 171 172 void setChainedPhi(PHINode *PN) { ChainedPhis.insert(PN); } 173 174 private: 175 LLVMContext &getContext() const { return SE.getContext(); } 176 177 /// InsertBinop - Insert the specified binary operator, doing a small amount 178 /// of work to avoid inserting an obviously redundant operation. 179 Value *InsertBinop(Instruction::BinaryOps Opcode, Value *LHS, Value *RHS); 180 181 /// ReuseOrCreateCast - Arange for there to be a cast of V to Ty at IP, 182 /// reusing an existing cast if a suitable one exists, moving an existing 183 /// cast if a suitable one exists but isn't in the right place, or 184 /// or creating a new one. 185 Value *ReuseOrCreateCast(Value *V, Type *Ty, 186 Instruction::CastOps Op, 187 BasicBlock::iterator IP); 188 189 /// InsertNoopCastOfTo - Insert a cast of V to the specified type, 190 /// which must be possible with a noop cast, doing what we can to 191 /// share the casts. 192 Value *InsertNoopCastOfTo(Value *V, Type *Ty); 193 194 /// expandAddToGEP - Expand a SCEVAddExpr with a pointer type into a GEP 195 /// instead of using ptrtoint+arithmetic+inttoptr. 196 Value *expandAddToGEP(const SCEV *const *op_begin, 197 const SCEV *const *op_end, 198 PointerType *PTy, Type *Ty, Value *V); 199 200 Value *expand(const SCEV *S); 201 202 /// expandCodeFor - Insert code to directly compute the specified SCEV 203 /// expression into the program. The inserted code is inserted into the 204 /// SCEVExpander's current insertion point. If a type is specified, the 205 /// result will be expanded to have that type, with a cast if necessary. 206 Value *expandCodeFor(const SCEV *SH, Type *Ty = 0); 207 208 /// isInsertedInstruction - Return true if the specified instruction was 209 /// inserted by the code rewriter. If so, the client should not modify the 210 /// instruction. 211 bool isInsertedInstruction(Instruction *I) const { 212 return InsertedValues.count(I) || InsertedPostIncValues.count(I); 213 } 214 215 /// getRelevantLoop - Determine the most "relevant" loop for the given SCEV. 216 const Loop *getRelevantLoop(const SCEV *); 217 218 Value *visitConstant(const SCEVConstant *S) { 219 return S->getValue(); 220 } 221 222 Value *visitTruncateExpr(const SCEVTruncateExpr *S); 223 224 Value *visitZeroExtendExpr(const SCEVZeroExtendExpr *S); 225 226 Value *visitSignExtendExpr(const SCEVSignExtendExpr *S); 227 228 Value *visitAddExpr(const SCEVAddExpr *S); 229 230 Value *visitMulExpr(const SCEVMulExpr *S); 231 232 Value *visitUDivExpr(const SCEVUDivExpr *S); 233 234 Value *visitAddRecExpr(const SCEVAddRecExpr *S); 235 236 Value *visitSMaxExpr(const SCEVSMaxExpr *S); 237 238 Value *visitUMaxExpr(const SCEVUMaxExpr *S); 239 240 Value *visitUnknown(const SCEVUnknown *S) { 241 return S->getValue(); 242 } 243 244 void rememberInstruction(Value *I); 245 246 void restoreInsertPoint(BasicBlock *BB, BasicBlock::iterator I); 247 248 bool isNormalAddRecExprPHI(PHINode *PN, Instruction *IncV, const Loop *L); 249 250 bool isExpandedAddRecExprPHI(PHINode *PN, Instruction *IncV, const Loop *L); 251 252 Value *expandAddRecExprLiterally(const SCEVAddRecExpr *); 253 PHINode *getAddRecExprPHILiterally(const SCEVAddRecExpr *Normalized, 254 const Loop *L, 255 Type *ExpandTy, 256 Type *IntTy); 257 Value *expandIVInc(PHINode *PN, Value *StepV, const Loop *L, 258 Type *ExpandTy, Type *IntTy, bool useSubtract); 259 }; 260} 261 262#endif 263