1 //===- llvm/Support/Options.h - Debug options 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 /// \file
9 /// This file declares helper objects for defining debug options that can be
10 /// configured via the command line. The new API currently builds on the cl::opt
11 /// API, but does not require the use of static globals.
12 ///
13 /// With this API options are registered during initialization. For passes, this
14 /// happens during pass initialization. Passes with options will call a static
15 /// registerOptions method during initialization that registers options with the
16 /// OptionRegistry. An example implementation of registerOptions is:
17 ///
18 /// static void registerOptions() {
19 ///   OptionRegistry::registerOption<bool, Scalarizer,
20 ///                                &Scalarizer::ScalarizeLoadStore>(
21 ///       "scalarize-load-store",
22 ///       "Allow the scalarizer pass to scalarize loads and store", false);
23 /// }
24 ///
25 /// When reading data for options the interface is via the LLVMContext. Option
26 /// data for passes should be read from the context during doInitialization. An
27 /// example of reading the above option would be:
28 ///
29 /// ScalarizeLoadStore =
30 ///   M.getContext().getOption<bool,
31 ///                            Scalarizer,
32 ///                            &Scalarizer::ScalarizeLoadStore>();
33 ///
34 //===----------------------------------------------------------------------===//
35 
36 #ifndef LLVM_SUPPORT_OPTIONS_H
37 #define LLVM_SUPPORT_OPTIONS_H
38 
39 #include "llvm/ADT/DenseMap.h"
40 #include "llvm/Support/CommandLine.h"
41 
42 namespace llvm {
43 
44 namespace detail {
45 
46 // Options are keyed of the unique address of a static character synthesized
47 // based on template arguments.
48 template <typename ValT, typename Base, ValT(Base::*Mem)> class OptionKey {
49 public:
50   static char ID;
51 };
52 
53 template <typename ValT, typename Base, ValT(Base::*Mem)>
54 char OptionKey<ValT, Base, Mem>::ID = 0;
55 
56 } // namespace detail
57 
58 /// Singleton class used to register debug options.
59 ///
60 /// The OptionRegistry is responsible for managing lifetimes of the options and
61 /// provides interfaces for option registration and reading values from options.
62 /// This object is a singleton, only one instance should ever exist so that all
63 /// options are registered in the same place.
64 class OptionRegistry {
65 private:
66   DenseMap<void *, cl::Option *> Options;
67 
68   /// Adds a cl::Option to the registry.
69   ///
70   /// \param Key unique key for option
71   /// \param O option to map to \p Key
72   ///
73   /// Allocated cl::Options are owned by the OptionRegistry and are deallocated
74   /// on destruction or removal
75   void addOption(void *Key, cl::Option *O);
76 
77 public:
78   ~OptionRegistry();
OptionRegistry()79   OptionRegistry() {}
80 
81   /// Returns a reference to the singleton instance.
82   static OptionRegistry &instance();
83 
84   /// Registers an option with the OptionRegistry singleton.
85   ///
86   /// \tparam ValT type of the option's data
87   /// \tparam Base class used to key the option
88   /// \tparam Mem member of \p Base used for keying the option
89   ///
90   /// Options are keyed off the template parameters to generate unique static
91   /// characters. The template parameters are (1) the type of the data the
92   /// option stores (\p ValT), the class that will read the option (\p Base),
93   /// and the member that the class will store the data into (\p Mem).
94   template <typename ValT, typename Base, ValT(Base::*Mem)>
registerOption(StringRef ArgStr,StringRef Desc,const ValT & InitValue)95   static void registerOption(StringRef ArgStr, StringRef Desc,
96                              const ValT &InitValue) {
97     cl::opt<ValT> *Option = new cl::opt<ValT>(ArgStr, cl::desc(Desc),
98                                               cl::Hidden, cl::init(InitValue));
99     instance().addOption(&detail::OptionKey<ValT, Base, Mem>::ID, Option);
100   }
101 
102   /// Returns the value of the option.
103   ///
104   /// \tparam ValT type of the option's data
105   /// \tparam Base class used to key the option
106   /// \tparam Mem member of \p Base used for keying the option
107   ///
108   /// Reads option values based on the key generated by the template parameters.
109   /// Keying for get() is the same as keying for registerOption.
get()110   template <typename ValT, typename Base, ValT(Base::*Mem)> ValT get() const {
111     auto It = Options.find(&detail::OptionKey<ValT, Base, Mem>::ID);
112     assert(It != Options.end() && "Option not in OptionRegistry");
113     return *(cl::opt<ValT> *)It->second;
114   }
115 };
116 
117 } // namespace llvm
118 
119 #endif
120