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