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/PostOrderIterator.h" 27 #include "llvm/ADT/SetVector.h" 28 #include "llvm/IR/IRBuilder.h" 29 #include "llvm/IR/Operator.h" 30 #include "llvm/IR/PassManager.h" 31 32 namespace llvm { 33 34 /// A private "module" namespace for types and utilities used by Reassociate. 35 /// These are implementation details and should not be used by clients. 36 namespace reassociate { 37 struct ValueEntry { 38 unsigned Rank; 39 Value *Op; 40 ValueEntry(unsigned R, Value *O) : Rank(R), Op(O) {} 41 }; 42 inline bool operator<(const ValueEntry &LHS, const ValueEntry &RHS) { 43 return LHS.Rank > RHS.Rank; // Sort so that highest rank goes to start. 44 } 45 46 /// \brief Utility class representing a base and exponent pair which form one 47 /// factor of some product. 48 struct Factor { 49 Value *Base; 50 unsigned Power; 51 Factor(Value *Base, unsigned Power) : Base(Base), Power(Power) {} 52 }; 53 54 class XorOpnd; 55 } 56 57 /// Reassociate commutative expressions. 58 class ReassociatePass : public PassInfoMixin<ReassociatePass> { 59 DenseMap<BasicBlock *, unsigned> RankMap; 60 DenseMap<AssertingVH<Value>, unsigned> ValueRankMap; 61 SetVector<AssertingVH<Instruction>> RedoInsts; 62 bool MadeChange; 63 64 public: 65 PreservedAnalyses run(Function &F, FunctionAnalysisManager &); 66 67 private: 68 void BuildRankMap(Function &F, ReversePostOrderTraversal<Function *> &RPOT); 69 unsigned getRank(Value *V); 70 void canonicalizeOperands(Instruction *I); 71 void ReassociateExpression(BinaryOperator *I); 72 void RewriteExprTree(BinaryOperator *I, 73 SmallVectorImpl<reassociate::ValueEntry> &Ops); 74 Value *OptimizeExpression(BinaryOperator *I, 75 SmallVectorImpl<reassociate::ValueEntry> &Ops); 76 Value *OptimizeAdd(Instruction *I, 77 SmallVectorImpl<reassociate::ValueEntry> &Ops); 78 Value *OptimizeXor(Instruction *I, 79 SmallVectorImpl<reassociate::ValueEntry> &Ops); 80 bool CombineXorOpnd(Instruction *I, reassociate::XorOpnd *Opnd1, 81 APInt &ConstOpnd, Value *&Res); 82 bool CombineXorOpnd(Instruction *I, reassociate::XorOpnd *Opnd1, 83 reassociate::XorOpnd *Opnd2, APInt &ConstOpnd, 84 Value *&Res); 85 bool collectMultiplyFactors(SmallVectorImpl<reassociate::ValueEntry> &Ops, 86 SmallVectorImpl<reassociate::Factor> &Factors); 87 Value *buildMinimalMultiplyDAG(IRBuilder<> &Builder, 88 SmallVectorImpl<reassociate::Factor> &Factors); 89 Value *OptimizeMul(BinaryOperator *I, 90 SmallVectorImpl<reassociate::ValueEntry> &Ops); 91 Value *RemoveFactorFromExpression(Value *V, Value *Factor); 92 void EraseInst(Instruction *I); 93 void RecursivelyEraseDeadInsts(Instruction *I, 94 SetVector<AssertingVH<Instruction>> &Insts); 95 void OptimizeInst(Instruction *I); 96 Instruction *canonicalizeNegConstExpr(Instruction *I); 97 }; 98 } 99 100 #endif // LLVM_TRANSFORMS_SCALAR_REASSOCIATE_H 101
