1 //===- Reassociate.h - Reassociate binary expressions -----------*- 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 pass reassociates commutative expressions in an order that is designed 11 // to promote better constant propagation, GCSE, LICM, PRE, etc. 12 // 13 // For example: 4 + (x + 5) -> x + (4 + 5) 14 // 15 // In the implementation of this algorithm, constants are assigned rank = 0, 16 // function arguments are rank = 1, and other values are assigned ranks 17 // corresponding to the reverse post order traversal of current function 18 // (starting at 2), which effectively gives values in deep loops higher rank 19 // than values not in loops. 20 // 21 //===----------------------------------------------------------------------===// 22 23 #ifndef LLVM_TRANSFORMS_SCALAR_REASSOCIATE_H 24 #define LLVM_TRANSFORMS_SCALAR_REASSOCIATE_H 25 26 #include "llvm/ADT/DenseMap.h" 27 #include "llvm/ADT/PostOrderIterator.h" 28 #include "llvm/ADT/SetVector.h" 29 #include "llvm/IR/IRBuilder.h" 30 #include "llvm/IR/PassManager.h" 31 #include "llvm/IR/ValueHandle.h" 32 33 namespace llvm { 34 35 class APInt; 36 class BasicBlock; 37 class BinaryOperator; 38 class Function; 39 class Instruction; 40 class Value; 41 42 /// A private "module" namespace for types and utilities used by Reassociate. 43 /// These are implementation details and should not be used by clients. 44 namespace reassociate { 45 46 struct ValueEntry { 47 unsigned Rank; 48 Value *Op; 49 50 ValueEntry(unsigned R, Value *O) : Rank(R), Op(O) {} 51 }; 52 53 inline bool operator<(const ValueEntry &LHS, const ValueEntry &RHS) { 54 return LHS.Rank > RHS.Rank; // Sort so that highest rank goes to start. 55 } 56 57 /// \brief Utility class representing a base and exponent pair which form one 58 /// factor of some product. 59 struct Factor { 60 Value *Base; 61 unsigned Power; 62 63 Factor(Value *Base, unsigned Power) : Base(Base), Power(Power) {} 64 }; 65 66 class XorOpnd; 67 68 } // end namespace reassociate 69 70 /// Reassociate commutative expressions. 71 class ReassociatePass : public PassInfoMixin<ReassociatePass> { 72 DenseMap<BasicBlock *, unsigned> RankMap; 73 DenseMap<AssertingVH<Value>, unsigned> ValueRankMap; 74 SetVector<AssertingVH<Instruction>> RedoInsts; 75 bool MadeChange; 76 77 public: 78 PreservedAnalyses run(Function &F, FunctionAnalysisManager &); 79 80 private: 81 void BuildRankMap(Function &F, ReversePostOrderTraversal<Function *> &RPOT); 82 unsigned getRank(Value *V); 83 void canonicalizeOperands(Instruction *I); 84 void ReassociateExpression(BinaryOperator *I); 85 void RewriteExprTree(BinaryOperator *I, 86 SmallVectorImpl<reassociate::ValueEntry> &Ops); 87 Value *OptimizeExpression(BinaryOperator *I, 88 SmallVectorImpl<reassociate::ValueEntry> &Ops); 89 Value *OptimizeAdd(Instruction *I, 90 SmallVectorImpl<reassociate::ValueEntry> &Ops); 91 Value *OptimizeXor(Instruction *I, 92 SmallVectorImpl<reassociate::ValueEntry> &Ops); 93 bool CombineXorOpnd(Instruction *I, reassociate::XorOpnd *Opnd1, 94 APInt &ConstOpnd, Value *&Res); 95 bool CombineXorOpnd(Instruction *I, reassociate::XorOpnd *Opnd1, 96 reassociate::XorOpnd *Opnd2, APInt &ConstOpnd, 97 Value *&Res); 98 Value *buildMinimalMultiplyDAG(IRBuilder<> &Builder, 99 SmallVectorImpl<reassociate::Factor> &Factors); 100 Value *OptimizeMul(BinaryOperator *I, 101 SmallVectorImpl<reassociate::ValueEntry> &Ops); 102 Value *RemoveFactorFromExpression(Value *V, Value *Factor); 103 void EraseInst(Instruction *I); 104 void RecursivelyEraseDeadInsts(Instruction *I, 105 SetVector<AssertingVH<Instruction>> &Insts); 106 void OptimizeInst(Instruction *I); 107 Instruction *canonicalizeNegConstExpr(Instruction *I); 108 }; 109 110 } // end namespace llvm 111 112 #endif // LLVM_TRANSFORMS_SCALAR_REASSOCIATE_H 113
