1 //===- llvm/IR/OptBisect.h - LLVM Bisect support ----------------*- 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 /// \file
10 /// This file declares the interface for bisecting optimizations.
11 ///
12 //===----------------------------------------------------------------------===//
13 
14 #ifndef LLVM_IR_OPTBISECT_H
15 #define LLVM_IR_OPTBISECT_H
16 
17 #include "llvm/ADT/StringRef.h"
18 #include "llvm/Support/ManagedStatic.h"
19 
20 namespace llvm {
21 
22 class Pass;
23 
24 /// Extensions to this class implement mechanisms to disable passes and
25 /// individual optimizations at compile time.
26 class OptPassGate {
27 public:
28   virtual ~OptPassGate() = default;
29 
30   /// IRDescription is a textual description of the IR unit the pass is running
31   /// over.
32   virtual bool shouldRunPass(const Pass *P, StringRef IRDescription) {
33     return true;
34   }
35 
36   /// isEnabled() should return true before calling shouldRunPass().
37   virtual bool isEnabled() const { return false; }
38 };
39 
40 /// This class implements a mechanism to disable passes and individual
41 /// optimizations at compile time based on a command line option
42 /// (-opt-bisect-limit) in order to perform a bisecting search for
43 /// optimization-related problems.
44 class OptBisect : public OptPassGate {
45 public:
46   /// Default constructor, initializes the OptBisect state based on the
47   /// -opt-bisect-limit command line argument.
48   ///
49   /// By default, bisection is disabled.
50   ///
51   /// Clients should not instantiate this class directly.  All access should go
52   /// through LLVMContext.
53   OptBisect();
54 
55   virtual ~OptBisect() = default;
56 
57   /// Checks the bisect limit to determine if the specified pass should run.
58   ///
59   /// This forwards to checkPass().
60   bool shouldRunPass(const Pass *P, StringRef IRDescription) override;
61 
62   /// isEnabled() should return true before calling shouldRunPass().
63   bool isEnabled() const override { return BisectEnabled; }
64 
65   /// Checks the bisect limit to determine if the specified pass should run.
66   ///
67   /// If the bisect limit is set to -1, the function prints a message describing
68   /// the pass and the bisect number assigned to it and return true.  Otherwise,
69   /// the function prints a message with the bisect number assigned to the
70   /// pass and indicating whether or not the pass will be run and return true if
71   /// the bisect limit has not yet been exceeded or false if it has.
72   ///
73   /// Most passes should not call this routine directly. Instead, they are
74   /// called through helper routines provided by the pass base classes.  For
75   /// instance, function passes should call FunctionPass::skipFunction().
76   bool checkPass(const StringRef PassName, const StringRef TargetDesc);
77 
78 private:
79   bool BisectEnabled = false;
80   unsigned LastBisectNum = 0;
81 };
82 
83 /// Singleton instance of the OptBisect class, so multiple pass managers don't
84 /// need to coordinate their uses of OptBisect.
85 extern ManagedStatic<OptBisect> OptBisector;
86 } // end namespace llvm
87 
88 #endif // LLVM_IR_OPTBISECT_H
89