1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
| //===- JumpThreading.h - thread control through conditional BBs -*- C++ -*-===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
//
/// \file
/// See the comments on JumpThreadingPass.
//
//===----------------------------------------------------------------------===//
#ifndef LLVM_TRANSFORMS_SCALAR_JUMPTHREADING_H
#define LLVM_TRANSFORMS_SCALAR_JUMPTHREADING_H
#include "llvm/ADT/ArrayRef.h"
#include "llvm/ADT/DenseSet.h"
#include "llvm/ADT/SmallPtrSet.h"
#include "llvm/ADT/SmallSet.h"
#include "llvm/ADT/SmallVector.h"
#include "llvm/Analysis/AliasAnalysis.h"
#include "llvm/Analysis/BlockFrequencyInfo.h"
#include "llvm/Analysis/BranchProbabilityInfo.h"
#include "llvm/Analysis/DomTreeUpdater.h"
#include "llvm/IR/ValueHandle.h"
#include <memory>
#include <utility>
namespace llvm {
class BasicBlock;
class BinaryOperator;
class BranchInst;
class CmpInst;
class Constant;
class DomTreeUpdater;
class Function;
class Instruction;
class IntrinsicInst;
class LazyValueInfo;
class LoadInst;
class PHINode;
class TargetLibraryInfo;
class Value;
/// A private "module" namespace for types and utilities used by
/// JumpThreading.
/// These are implementation details and should not be used by clients.
namespace jumpthreading {
// These are at global scope so static functions can use them too.
using PredValueInfo = SmallVectorImpl<std::pair<Constant *, BasicBlock *>>;
using PredValueInfoTy = SmallVector<std::pair<Constant *, BasicBlock *>, 8>;
// This is used to keep track of what kind of constant we're currently hoping
// to find.
enum ConstantPreference { WantInteger, WantBlockAddress };
} // end namespace jumpthreading
/// This pass performs 'jump threading', which looks at blocks that have
/// multiple predecessors and multiple successors. If one or more of the
/// predecessors of the block can be proven to always jump to one of the
/// successors, we forward the edge from the predecessor to the successor by
/// duplicating the contents of this block.
///
/// An example of when this can occur is code like this:
///
/// if () { ...
/// X = 4;
/// }
/// if (X < 3) {
///
/// In this case, the unconditional branch at the end of the first if can be
/// revectored to the false side of the second if.
class JumpThreadingPass : public PassInfoMixin<JumpThreadingPass> {
TargetLibraryInfo *TLI;
LazyValueInfo *LVI;
AliasAnalysis *AA;
DomTreeUpdater *DTU;
std::unique_ptr<BlockFrequencyInfo> BFI;
std::unique_ptr<BranchProbabilityInfo> BPI;
bool HasProfileData = false;
bool HasGuards = false;
#ifdef NDEBUG
SmallPtrSet<const BasicBlock *, 16> LoopHeaders;
#else
SmallSet<AssertingVH<const BasicBlock>, 16> LoopHeaders;
#endif
unsigned BBDupThreshold;
public:
JumpThreadingPass(int T = -1);
// Glue for old PM.
bool runImpl(Function &F, TargetLibraryInfo *TLI_, LazyValueInfo *LVI_,
AliasAnalysis *AA_, DomTreeUpdater *DTU_, bool HasProfileData_,
std::unique_ptr<BlockFrequencyInfo> BFI_,
std::unique_ptr<BranchProbabilityInfo> BPI_);
PreservedAnalyses run(Function &F, FunctionAnalysisManager &AM);
void releaseMemory() {
BFI.reset();
BPI.reset();
}
void FindLoopHeaders(Function &F);
bool ProcessBlock(BasicBlock *BB);
bool ThreadEdge(BasicBlock *BB, const SmallVectorImpl<BasicBlock *> &PredBBs,
BasicBlock *SuccBB);
bool DuplicateCondBranchOnPHIIntoPred(
BasicBlock *BB, const SmallVectorImpl<BasicBlock *> &PredBBs);
bool ComputeValueKnownInPredecessorsImpl(
Value *V, BasicBlock *BB, jumpthreading::PredValueInfo &Result,
jumpthreading::ConstantPreference Preference,
DenseSet<std::pair<Value *, BasicBlock *>> &RecursionSet,
Instruction *CxtI = nullptr);
bool
ComputeValueKnownInPredecessors(Value *V, BasicBlock *BB,
jumpthreading::PredValueInfo &Result,
jumpthreading::ConstantPreference Preference,
Instruction *CxtI = nullptr) {
DenseSet<std::pair<Value *, BasicBlock *>> RecursionSet;
return ComputeValueKnownInPredecessorsImpl(V, BB, Result, Preference,
RecursionSet, CxtI);
}
bool ProcessThreadableEdges(Value *Cond, BasicBlock *BB,
jumpthreading::ConstantPreference Preference,
Instruction *CxtI = nullptr);
bool ProcessBranchOnPHI(PHINode *PN);
bool ProcessBranchOnXOR(BinaryOperator *BO);
bool ProcessImpliedCondition(BasicBlock *BB);
bool SimplifyPartiallyRedundantLoad(LoadInst *LI);
void UnfoldSelectInstr(BasicBlock *Pred, BasicBlock *BB, SelectInst *SI,
PHINode *SIUse, unsigned Idx);
bool TryToUnfoldSelect(CmpInst *CondCmp, BasicBlock *BB);
bool TryToUnfoldSelect(SwitchInst *SI, BasicBlock *BB);
bool TryToUnfoldSelectInCurrBB(BasicBlock *BB);
bool ProcessGuards(BasicBlock *BB);
bool ThreadGuard(BasicBlock *BB, IntrinsicInst *Guard, BranchInst *BI);
private:
BasicBlock *SplitBlockPreds(BasicBlock *BB, ArrayRef<BasicBlock *> Preds,
const char *Suffix);
void UpdateBlockFreqAndEdgeWeight(BasicBlock *PredBB, BasicBlock *BB,
BasicBlock *NewBB, BasicBlock *SuccBB);
/// Check if the block has profile metadata for its outgoing edges.
bool doesBlockHaveProfileData(BasicBlock *BB);
};
} // end namespace llvm
#endif // LLVM_TRANSFORMS_SCALAR_JUMPTHREADING_H
|