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/PassManager.h"
29#include "llvm/IR/ValueHandle.h"
30#include <deque>
31
32namespace llvm {
33
34class APInt;
35class BasicBlock;
36class BinaryOperator;
37class Function;
38class Instruction;
39class IRBuilderBase;
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 bool HasNUW);
107 Value *OptimizeExpression(BinaryOperator *I,
108 SmallVectorImpl<reassociate::ValueEntry> &Ops);
109 Value *OptimizeAdd(Instruction *I,
110 SmallVectorImpl<reassociate::ValueEntry> &Ops);
111 Value *OptimizeXor(Instruction *I,
112 SmallVectorImpl<reassociate::ValueEntry> &Ops);
113 bool CombineXorOpnd(Instruction *I, reassociate::XorOpnd *Opnd1,
114 APInt &ConstOpnd, Value *&Res);
115 bool CombineXorOpnd(Instruction *I, reassociate::XorOpnd *Opnd1,
116 reassociate::XorOpnd *Opnd2, APInt &ConstOpnd,
117 Value *&Res);
118 Value *buildMinimalMultiplyDAG(IRBuilderBase &Builder,
119 SmallVectorImpl<reassociate::Factor> &Factors);
120 Value *OptimizeMul(BinaryOperator *I,
121 SmallVectorImpl<reassociate::ValueEntry> &Ops);
122 Value *RemoveFactorFromExpression(Value *V, Value *Factor);
123 void EraseInst(Instruction *I);
124 void RecursivelyEraseDeadInsts(Instruction *I, OrderedSet &Insts);
125 void OptimizeInst(Instruction *I);
126 Instruction *canonicalizeNegFPConstantsForOp(Instruction *I, Instruction *Op,
127 Value *OtherOp);
128 Instruction *canonicalizeNegFPConstants(Instruction *I);
129 void BuildPairMap(ReversePostOrderTraversal<Function *> &RPOT);
130};
131
132} // end namespace llvm
133
134#endif // LLVM_TRANSFORMS_SCALAR_REASSOCIATE_H
135

source code of llvm/include/llvm/Transforms/Scalar/Reassociate.h