ScalarEvolutionExpander.h revision 9269926bfb713e92e328e9578c6d8826c68dcb9d
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/Support/IRBuilder.h" 19#include "llvm/Support/TargetFolder.h" 20#include <set> 21 22namespace llvm { 23 /// SCEVExpander - This class uses information about analyze scalars to 24 /// rewrite expressions in canonical form. 25 /// 26 /// Clients should create an instance of this class when rewriting is needed, 27 /// and destroy it when finished to allow the release of the associated 28 /// memory. 29 class SCEVExpander : public SCEVVisitor<SCEVExpander, Value*> { 30 ScalarEvolution &SE; 31 std::map<std::pair<const SCEV *, Instruction *>, AssertingVH<Value> > 32 InsertedExpressions; 33 std::set<Value*> InsertedValues; 34 35 /// PostIncLoop - When non-null, expanded addrecs referring to the given 36 /// loop expanded in post-inc mode. For example, expanding {1,+,1}<L> in 37 /// post-inc mode returns the add instruction that adds one to the phi 38 /// for {0,+,1}<L>, as opposed to a new phi starting at 1. This is only 39 /// supported in non-canonical mode. 40 const Loop *PostIncLoop; 41 42 /// IVIncInsertPos - When this is non-null, addrecs expanded in the 43 /// loop it indicates should be inserted with increments at 44 /// IVIncInsertPos. 45 const Loop *IVIncInsertLoop; 46 47 /// IVIncInsertPos - When expanding addrecs in the IVIncInsertLoop loop, 48 /// insert the IV increment at this position. 49 Instruction *IVIncInsertPos; 50 51 /// CanonicalMode - When true, expressions are expanded in "canonical" 52 /// form. In particular, addrecs are expanded as arithmetic based on 53 /// a canonical induction variable. When false, expression are expanded 54 /// in a more literal form. 55 bool CanonicalMode; 56 57 typedef IRBuilder<true, TargetFolder> BuilderType; 58 BuilderType Builder; 59 60 friend struct SCEVVisitor<SCEVExpander, Value*>; 61 62 public: 63 /// SCEVExpander - Construct a SCEVExpander in "canonical" mode. 64 explicit SCEVExpander(ScalarEvolution &se) 65 : SE(se), PostIncLoop(0), IVIncInsertLoop(0), CanonicalMode(true), 66 Builder(se.getContext(), TargetFolder(se.TD)) {} 67 68 /// clear - Erase the contents of the InsertedExpressions map so that users 69 /// trying to expand the same expression into multiple BasicBlocks or 70 /// different places within the same BasicBlock can do so. 71 void clear() { InsertedExpressions.clear(); } 72 73 /// getOrInsertCanonicalInductionVariable - This method returns the 74 /// canonical induction variable of the specified type for the specified 75 /// loop (inserting one if there is none). A canonical induction variable 76 /// starts at zero and steps by one on each iteration. 77 Value *getOrInsertCanonicalInductionVariable(const Loop *L, const Type *Ty); 78 79 /// expandCodeFor - Insert code to directly compute the specified SCEV 80 /// expression into the program. The inserted code is inserted into the 81 /// specified block. 82 Value *expandCodeFor(const SCEV *SH, const Type *Ty, Instruction *I) { 83 BasicBlock::iterator IP = I; 84 while (isInsertedInstruction(IP)) ++IP; 85 Builder.SetInsertPoint(IP->getParent(), IP); 86 return expandCodeFor(SH, Ty); 87 } 88 89 /// setIVIncInsertPos - Set the current IV increment loop and position. 90 void setIVIncInsertPos(const Loop *L, Instruction *Pos) { 91 assert(!CanonicalMode && 92 "IV increment positions are not supported in CanonicalMode"); 93 IVIncInsertLoop = L; 94 IVIncInsertPos = Pos; 95 } 96 97 /// setPostInc - If L is non-null, enable post-inc expansion for addrecs 98 /// referring to the given loop. If L is null, disable post-inc expansion 99 /// completely. Post-inc expansion is only supported in non-canonical 100 /// mode. 101 void setPostInc(const Loop *L) { 102 assert(!CanonicalMode && 103 "Post-inc expansion is not supported in CanonicalMode"); 104 PostIncLoop = L; 105 } 106 107 /// disableCanonicalMode - Disable the behavior of expanding expressions in 108 /// canonical form rather than in a more literal form. Non-canonical mode 109 /// is useful for late optimization passes. 110 void disableCanonicalMode() { CanonicalMode = false; } 111 112 private: 113 LLVMContext &getContext() const { return SE.getContext(); } 114 115 /// InsertBinop - Insert the specified binary operator, doing a small amount 116 /// of work to avoid inserting an obviously redundant operation. 117 Value *InsertBinop(Instruction::BinaryOps Opcode, Value *LHS, Value *RHS); 118 119 /// InsertNoopCastOfTo - Insert a cast of V to the specified type, 120 /// which must be possible with a noop cast, doing what we can to 121 /// share the casts. 122 Value *InsertNoopCastOfTo(Value *V, const Type *Ty); 123 124 /// expandAddToGEP - Expand a SCEVAddExpr with a pointer type into a GEP 125 /// instead of using ptrtoint+arithmetic+inttoptr. 126 Value *expandAddToGEP(const SCEV *const *op_begin, 127 const SCEV *const *op_end, 128 const PointerType *PTy, const Type *Ty, Value *V); 129 130 Value *expand(const SCEV *S); 131 132 /// expandCodeFor - Insert code to directly compute the specified SCEV 133 /// expression into the program. The inserted code is inserted into the 134 /// SCEVExpander's current insertion point. If a type is specified, the 135 /// result will be expanded to have that type, with a cast if necessary. 136 Value *expandCodeFor(const SCEV *SH, const Type *Ty = 0); 137 138 /// isInsertedInstruction - Return true if the specified instruction was 139 /// inserted by the code rewriter. If so, the client should not modify the 140 /// instruction. 141 bool isInsertedInstruction(Instruction *I) const { 142 return InsertedValues.count(I); 143 } 144 145 Value *visitConstant(const SCEVConstant *S) { 146 return S->getValue(); 147 } 148 149 Value *visitTruncateExpr(const SCEVTruncateExpr *S); 150 151 Value *visitZeroExtendExpr(const SCEVZeroExtendExpr *S); 152 153 Value *visitSignExtendExpr(const SCEVSignExtendExpr *S); 154 155 Value *visitAddExpr(const SCEVAddExpr *S); 156 157 Value *visitMulExpr(const SCEVMulExpr *S); 158 159 Value *visitUDivExpr(const SCEVUDivExpr *S); 160 161 Value *visitAddRecExpr(const SCEVAddRecExpr *S); 162 163 Value *visitSMaxExpr(const SCEVSMaxExpr *S); 164 165 Value *visitUMaxExpr(const SCEVUMaxExpr *S); 166 167 Value *visitUnknown(const SCEVUnknown *S) { 168 return S->getValue(); 169 } 170 171 void rememberInstruction(Value *I) { 172 if (!PostIncLoop) InsertedValues.insert(I); 173 } 174 175 Value *expandAddRecExprLiterally(const SCEVAddRecExpr *); 176 PHINode *getAddRecExprPHILiterally(const SCEVAddRecExpr *Normalized, 177 const Loop *L, 178 const Type *ExpandTy, 179 const Type *IntTy); 180 }; 181} 182 183#endif 184