1 //===- AllocatorBase.h - Simple memory allocation abstraction ---*- 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 ///
10 /// This file defines MallocAllocator. MallocAllocator conforms to the LLVM
11 /// "Allocator" concept which consists of an Allocate method accepting a size
12 /// and alignment, and a Deallocate accepting a pointer and size. Further, the
13 /// LLVM "Allocator" concept has overloads of Allocate and Deallocate for
14 /// setting size and alignment based on the final type. These overloads are
15 /// typically provided by a base class template \c AllocatorBase.
16 ///
17 //===----------------------------------------------------------------------===//
18 
19 #ifndef LLVM_SUPPORT_ALLOCATORBASE_H
20 #define LLVM_SUPPORT_ALLOCATORBASE_H
21 
22 #include "llvm/Support/Compiler.h"
23 #include "llvm/Support/MemAlloc.h"
24 #include <type_traits>
25 
26 namespace llvm {
27 
28 /// CRTP base class providing obvious overloads for the core \c
29 /// Allocate() methods of LLVM-style allocators.
30 ///
31 /// This base class both documents the full public interface exposed by all
32 /// LLVM-style allocators, and redirects all of the overloads to a single core
33 /// set of methods which the derived class must define.
34 template <typename DerivedT> class AllocatorBase {
35 public:
36   /// Allocate \a Size bytes of \a Alignment aligned memory. This method
37   /// must be implemented by \c DerivedT.
38   void *Allocate(size_t Size, size_t Alignment) {
39 #ifdef __clang__
40     static_assert(static_cast<void *(AllocatorBase::*)(size_t, size_t)>(
41                       &AllocatorBase::Allocate) !=
42                       static_cast<void *(DerivedT::*)(size_t, size_t)>(
43                           &DerivedT::Allocate),
44                   "Class derives from AllocatorBase without implementing the "
45                   "core Allocate(size_t, size_t) overload!");
46 #endif
47     return static_cast<DerivedT *>(this)->Allocate(Size, Alignment);
48   }
49 
50   /// Deallocate \a Ptr to \a Size bytes of memory allocated by this
51   /// allocator.
52   void Deallocate(const void *Ptr, size_t Size, size_t Alignment) {
53 #ifdef __clang__
54     static_assert(
55         static_cast<void (AllocatorBase::*)(const void *, size_t, size_t)>(
56             &AllocatorBase::Deallocate) !=
57             static_cast<void (DerivedT::*)(const void *, size_t, size_t)>(
58                 &DerivedT::Deallocate),
59         "Class derives from AllocatorBase without implementing the "
60         "core Deallocate(void *) overload!");
61 #endif
62     return static_cast<DerivedT *>(this)->Deallocate(Ptr, Size, Alignment);
63   }
64 
65   // The rest of these methods are helpers that redirect to one of the above
66   // core methods.
67 
68   /// Allocate space for a sequence of objects without constructing them.
69   template <typename T> T *Allocate(size_t Num = 1) {
70     return static_cast<T *>(Allocate(Num * sizeof(T), alignof(T)));
71   }
72 
73   /// Deallocate space for a sequence of objects without constructing them.
74   template <typename T>
75   std::enable_if_t<!std::is_same<std::remove_cv_t<T>, void>::value, void>
76   Deallocate(T *Ptr, size_t Num = 1) {
77     Deallocate(static_cast<const void *>(Ptr), Num * sizeof(T), alignof(T));
78   }
79 };
80 
81 class MallocAllocator : public AllocatorBase<MallocAllocator> {
82 public:
83   void Reset() {}
84 
85   LLVM_ATTRIBUTE_RETURNS_NONNULL void *Allocate(size_t Size, size_t Alignment) {
86     return allocate_buffer(Size, Alignment);
87   }
88 
89   // Pull in base class overloads.
90   using AllocatorBase<MallocAllocator>::Allocate;
91 
92   void Deallocate(const void *Ptr, size_t Size, size_t Alignment) {
93     deallocate_buffer(const_cast<void *>(Ptr), Size, Alignment);
94   }
95 
96   // Pull in base class overloads.
97   using AllocatorBase<MallocAllocator>::Deallocate;
98 
99   void PrintStats() const {}
100 };
101 
102 namespace detail {
103 
104 template <typename Alloc> class AllocatorHolder : Alloc {
105 public:
106   AllocatorHolder() = default;
107   AllocatorHolder(const Alloc &A) : Alloc(A) {}
108   AllocatorHolder(Alloc &&A) : Alloc(static_cast<Alloc &&>(A)) {}
109   Alloc &getAllocator() { return *this; }
110   const Alloc &getAllocator() const { return *this; }
111 };
112 
113 template <typename Alloc> class AllocatorHolder<Alloc &> {
114   Alloc &A;
115 
116 public:
117   AllocatorHolder(Alloc &A) : A(A) {}
118   Alloc &getAllocator() { return A; }
119   const Alloc &getAllocator() const { return A; }
120 };
121 
122 } // namespace detail
123 
124 } // namespace llvm
125 
126 #endif // LLVM_SUPPORT_ALLOCATORBASE_H
127