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       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             : #include <deque>
      33             : 
      34             : namespace llvm {
      35             : 
      36             : class APInt;
      37             : class BasicBlock;
      38             : class BinaryOperator;
      39             : class Function;
      40             : class Instruction;
      41             : class Value;
      42             : 
      43             : /// A private "module" namespace for types and utilities used by Reassociate.
      44             : /// These are implementation details and should not be used by clients.
      45             : namespace reassociate {
      46             : 
      47             : struct ValueEntry {
      48             :   unsigned Rank;
      49             :   Value *Op;
      50             : 
      51     1768100 :   ValueEntry(unsigned R, Value *O) : Rank(R), Op(O) {}
      52             : };
      53             : 
      54           0 : inline bool operator<(const ValueEntry &LHS, const ValueEntry &RHS) {
      55           0 :   return LHS.Rank > RHS.Rank; // Sort so that highest rank goes to start.
      56             : }
      57             : 
      58             : /// Utility class representing a base and exponent pair which form one
      59             : /// factor of some product.
      60             : struct Factor {
      61             :   Value *Base;
      62             :   unsigned Power;
      63             : 
      64          20 :   Factor(Value *Base, unsigned Power) : Base(Base), Power(Power) {}
      65             : };
      66             : 
      67             : class XorOpnd;
      68             : 
      69             : } // end namespace reassociate
      70             : 
      71             : /// Reassociate commutative expressions.
      72             : class ReassociatePass : public PassInfoMixin<ReassociatePass> {
      73             : public:
      74             :   using OrderedSet =
      75             :       SetVector<AssertingVH<Instruction>, std::deque<AssertingVH<Instruction>>>;
      76             : 
      77             : protected:
      78             :   DenseMap<BasicBlock *, unsigned> RankMap;
      79             :   DenseMap<AssertingVH<Value>, unsigned> ValueRankMap;
      80             :   OrderedSet RedoInsts;
      81             : 
      82             :   // Arbitrary, but prevents quadratic behavior.
      83             :   static const unsigned GlobalReassociateLimit = 10;
      84             :   static const unsigned NumBinaryOps =
      85             :       Instruction::BinaryOpsEnd - Instruction::BinaryOpsBegin;
      86             :   DenseMap<std::pair<Value *, Value *>, unsigned> PairMap[NumBinaryOps];
      87             : 
      88             :   bool MadeChange;
      89             : 
      90             : public:
      91             :   PreservedAnalyses run(Function &F, FunctionAnalysisManager &);
      92             : 
      93             : private:
      94             :   void BuildRankMap(Function &F, ReversePostOrderTraversal<Function *> &RPOT);
      95             :   unsigned getRank(Value *V);
      96             :   void canonicalizeOperands(Instruction *I);
      97             :   void ReassociateExpression(BinaryOperator *I);
      98             :   void RewriteExprTree(BinaryOperator *I,
      99             :                        SmallVectorImpl<reassociate::ValueEntry> &Ops);
     100             :   Value *OptimizeExpression(BinaryOperator *I,
     101             :                             SmallVectorImpl<reassociate::ValueEntry> &Ops);
     102             :   Value *OptimizeAdd(Instruction *I,
     103             :                      SmallVectorImpl<reassociate::ValueEntry> &Ops);
     104             :   Value *OptimizeXor(Instruction *I,
     105             :                      SmallVectorImpl<reassociate::ValueEntry> &Ops);
     106             :   bool CombineXorOpnd(Instruction *I, reassociate::XorOpnd *Opnd1,
     107             :                       APInt &ConstOpnd, Value *&Res);
     108             :   bool CombineXorOpnd(Instruction *I, reassociate::XorOpnd *Opnd1,
     109             :                       reassociate::XorOpnd *Opnd2, APInt &ConstOpnd,
     110             :                       Value *&Res);
     111             :   Value *buildMinimalMultiplyDAG(IRBuilder<> &Builder,
     112             :                                  SmallVectorImpl<reassociate::Factor> &Factors);
     113             :   Value *OptimizeMul(BinaryOperator *I,
     114             :                      SmallVectorImpl<reassociate::ValueEntry> &Ops);
     115             :   Value *RemoveFactorFromExpression(Value *V, Value *Factor);
     116             :   void EraseInst(Instruction *I);
     117             :   void RecursivelyEraseDeadInsts(Instruction *I, OrderedSet &Insts);
     118             :   void OptimizeInst(Instruction *I);
     119             :   Instruction *canonicalizeNegConstExpr(Instruction *I);
     120             :   void BuildPairMap(ReversePostOrderTraversal<Function *> &RPOT);
     121             : };
     122             : 
     123             : } // end namespace llvm
     124             : 
     125             : #endif // LLVM_TRANSFORMS_SCALAR_REASSOCIATE_H