1//===- Reassociate.h - Reassociate binary expressions -----------*- C++ -*-===// 2// 3// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions. 4// See https://llvm.org/LICENSE.txt for license information. 5// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception 6// 7//===----------------------------------------------------------------------===// 8// 9// This pass reassociates commutative expressions in an order that is designed 10// to promote better constant propagation, GCSE, LICM, PRE, etc. 11// 12// For example: 4 + (x + 5) -> x + (4 + 5) 13// 14// In the implementation of this algorithm, constants are assigned rank = 0, 15// function arguments are rank = 1, and other values are assigned ranks 16// corresponding to the reverse post order traversal of current function 17// (starting at 2), which effectively gives values in deep loops higher rank 18// than values not in loops. 19// 20//===----------------------------------------------------------------------===// 21 22#ifndef LLVM_TRANSFORMS_SCALAR_REASSOCIATE_H 23#define LLVM_TRANSFORMS_SCALAR_REASSOCIATE_H 24 25#include "llvm/ADT/DenseMap.h" 26#include "llvm/ADT/PostOrderIterator.h" 27#include "llvm/ADT/SetVector.h" 28#include "llvm/IR/IRBuilder.h" 29#include "llvm/IR/PassManager.h" 30#include "llvm/IR/ValueHandle.h" 31#include <deque> 32 33namespace llvm { 34 35class APInt; 36class BasicBlock; 37class BinaryOperator; 38class Function; 39class Instruction; 40class 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. 44namespace reassociate { 45 46struct ValueEntry { 47 unsigned Rank; 48 Value *Op; 49 50 ValueEntry(unsigned R, Value *O) : Rank(R), Op(O) {} 51}; 52 53inline 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/// Utility class representing a base and exponent pair which form one 58/// factor of some product. 59struct Factor { 60 Value *Base; 61 unsigned Power; 62 63 Factor(Value *Base, unsigned Power) : Base(Base), Power(Power) {} 64}; 65 66class XorOpnd; 67 68} // end namespace reassociate 69 70/// Reassociate commutative expressions. 71class ReassociatePass : public PassInfoMixin<ReassociatePass> { 72public: 73 using OrderedSet = 74 SetVector<AssertingVH<Instruction>, std::deque<AssertingVH<Instruction>>>; 75 76protected: 77 DenseMap<BasicBlock *, unsigned> RankMap; 78 DenseMap<AssertingVH<Value>, unsigned> ValueRankMap; 79 OrderedSet RedoInsts; 80 81 // Arbitrary, but prevents quadratic behavior. 82 static const unsigned GlobalReassociateLimit = 10; 83 static const unsigned NumBinaryOps = 84 Instruction::BinaryOpsEnd - Instruction::BinaryOpsBegin; 85 86 struct PairMapValue { 87 WeakVH Value1; 88 WeakVH Value2; 89 unsigned Score; 90 bool isValid() const { return Value1 && Value2; } 91 }; 92 DenseMap<std::pair<Value *, Value *>, PairMapValue> PairMap[NumBinaryOps]; 93 94 bool MadeChange; 95 96public: 97 PreservedAnalyses run(Function &F, FunctionAnalysisManager &); 98 99private: 100 void BuildRankMap(Function &F, ReversePostOrderTraversal<Function *> &RPOT); 101 unsigned getRank(Value *V); 102 void canonicalizeOperands(Instruction *I); 103 void ReassociateExpression(BinaryOperator *I); 104 void RewriteExprTree(BinaryOperator *I, 105 SmallVectorImpl<reassociate::ValueEntry> &Ops); 106 Value *OptimizeExpression(BinaryOperator *I, 107 SmallVectorImpl<reassociate::ValueEntry> &Ops); 108 Value *OptimizeAdd(Instruction *I, 109 SmallVectorImpl<reassociate::ValueEntry> &Ops); 110 Value *OptimizeXor(Instruction *I, 111 SmallVectorImpl<reassociate::ValueEntry> &Ops); 112 bool CombineXorOpnd(Instruction *I, reassociate::XorOpnd *Opnd1, 113 APInt &ConstOpnd, Value *&Res); 114 bool CombineXorOpnd(Instruction *I, reassociate::XorOpnd *Opnd1, 115 reassociate::XorOpnd *Opnd2, APInt &ConstOpnd, 116 Value *&Res); 117 Value *buildMinimalMultiplyDAG(IRBuilder<> &Builder, 118 SmallVectorImpl<reassociate::Factor> &Factors); 119 Value *OptimizeMul(BinaryOperator *I, 120 SmallVectorImpl<reassociate::ValueEntry> &Ops); 121 Value *RemoveFactorFromExpression(Value *V, Value *Factor); 122 void EraseInst(Instruction *I); 123 void RecursivelyEraseDeadInsts(Instruction *I, OrderedSet &Insts); 124 void OptimizeInst(Instruction *I); 125 Instruction *canonicalizeNegFPConstantsForOp(Instruction *I, Instruction *Op, 126 Value *OtherOp); 127 Instruction *canonicalizeNegFPConstants(Instruction *I); 128 void BuildPairMap(ReversePostOrderTraversal<Function *> &RPOT); 129}; 130 131} // end namespace llvm 132 133#endif // LLVM_TRANSFORMS_SCALAR_REASSOCIATE_H 134