1//===- LazyValueInfo.h - Value constraint analysis --------------*- 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 file defines the interface for lazy computation of value constraint
11// information.
12//
13//===----------------------------------------------------------------------===//
14
15#ifndef LLVM_ANALYSIS_LAZYVALUEINFO_H
16#define LLVM_ANALYSIS_LAZYVALUEINFO_H
17
18#include "llvm/Pass.h"
19
20namespace llvm {
21  class AssumptionCache;
22  class Constant;
23  class DataLayout;
24  class DominatorTree;
25  class Instruction;
26  class TargetLibraryInfo;
27  class Value;
28
29/// This pass computes, caches, and vends lazy value constraint information.
30class LazyValueInfo : public FunctionPass {
31  AssumptionCache *AC;
32  class TargetLibraryInfo *TLI;
33  DominatorTree *DT;
34  void *PImpl;
35  LazyValueInfo(const LazyValueInfo&) = delete;
36  void operator=(const LazyValueInfo&) = delete;
37public:
38  static char ID;
39  LazyValueInfo() : FunctionPass(ID), PImpl(nullptr) {
40    initializeLazyValueInfoPass(*PassRegistry::getPassRegistry());
41  }
42  ~LazyValueInfo() override { assert(!PImpl && "releaseMemory not called"); }
43
44  /// This is used to return true/false/dunno results.
45  enum Tristate {
46    Unknown = -1, False = 0, True = 1
47  };
48
49  // Public query interface.
50
51  /// Determine whether the specified value comparison with a constant is known
52  /// to be true or false on the specified CFG edge.
53  /// Pred is a CmpInst predicate.
54  Tristate getPredicateOnEdge(unsigned Pred, Value *V, Constant *C,
55                              BasicBlock *FromBB, BasicBlock *ToBB,
56                              Instruction *CxtI = nullptr);
57
58  /// Determine whether the specified value comparison with a constant is known
59  /// to be true or false at the specified instruction
60  /// (from an assume intrinsic). Pred is a CmpInst predicate.
61  Tristate getPredicateAt(unsigned Pred, Value *V, Constant *C,
62                          Instruction *CxtI);
63
64  /// Determine whether the specified value is known to be a
65  /// constant at the end of the specified block.  Return null if not.
66  Constant *getConstant(Value *V, BasicBlock *BB, Instruction *CxtI = nullptr);
67
68  /// Determine whether the specified value is known to be a
69  /// constant on the specified edge.  Return null if not.
70  Constant *getConstantOnEdge(Value *V, BasicBlock *FromBB, BasicBlock *ToBB,
71                              Instruction *CxtI = nullptr);
72
73  /// Inform the analysis cache that we have threaded an edge from
74  /// PredBB to OldSucc to be from PredBB to NewSucc instead.
75  void threadEdge(BasicBlock *PredBB, BasicBlock *OldSucc, BasicBlock *NewSucc);
76
77  /// Inform the analysis cache that we have erased a block.
78  void eraseBlock(BasicBlock *BB);
79
80  // Implementation boilerplate.
81
82  void getAnalysisUsage(AnalysisUsage &AU) const override;
83  void releaseMemory() override;
84  bool runOnFunction(Function &F) override;
85};
86
87}  // end namespace llvm
88
89#endif
90
91