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 
25 namespace llvm {
26 
27 /// CRTP base class providing obvious overloads for the core \c
28 /// Allocate() methods of LLVM-style allocators.
29 ///
30 /// This base class both documents the full public interface exposed by all
31 /// LLVM-style allocators, and redirects all of the overloads to a single core
32 /// set of methods which the derived class must define.
33 template <typename DerivedT> class AllocatorBase {
34 public:
35   /// Allocate \a Size bytes of \a Alignment aligned memory. This method
36   /// must be implemented by \c DerivedT.
37   void *Allocate(size_t Size, size_t Alignment) {
38 #ifdef __clang__
39     static_assert(static_cast<void *(AllocatorBase::*)(size_t, size_t)>(
40                       &AllocatorBase::Allocate) !=
41                       static_cast<void *(DerivedT::*)(size_t, size_t)>(
42                           &DerivedT::Allocate),
43                   "Class derives from AllocatorBase without implementing the "
44                   "core Allocate(size_t, size_t) overload!");
45 #endif
46     return static_cast<DerivedT *>(this)->Allocate(Size, Alignment);
47   }
48 
49   /// Deallocate \a Ptr to \a Size bytes of memory allocated by this
50   /// allocator.
51   void Deallocate(const void *Ptr, size_t Size, size_t Alignment) {
52 #ifdef __clang__
53     static_assert(
54         static_cast<void (AllocatorBase::*)(const void *, size_t, size_t)>(
55             &AllocatorBase::Deallocate) !=
56             static_cast<void (DerivedT::*)(const void *, size_t, size_t)>(
57                 &DerivedT::Deallocate),
58         "Class derives from AllocatorBase without implementing the "
59         "core Deallocate(void *) overload!");
60 #endif
61     return static_cast<DerivedT *>(this)->Deallocate(Ptr, Size, Alignment);
62   }
63 
64   // The rest of these methods are helpers that redirect to one of the above
65   // core methods.
66 
67   /// Allocate space for a sequence of objects without constructing them.
68   template <typename T> T *Allocate(size_t Num = 1) {
69     return static_cast<T *>(Allocate(Num * sizeof(T), alignof(T)));
70   }
71 
72   /// Deallocate space for a sequence of objects without constructing them.
73   template <typename T>
74   std::enable_if_t<!std::is_same<std::remove_cv_t<T>, void>::value, void>
75   Deallocate(T *Ptr, size_t Num = 1) {
76     Deallocate(static_cast<const void *>(Ptr), Num * sizeof(T), alignof(T));
77   }
78 };
79 
80 class MallocAllocator : public AllocatorBase<MallocAllocator> {
81 public:
82   void Reset() {}
83 
84   LLVM_ATTRIBUTE_RETURNS_NONNULL void *Allocate(size_t Size, size_t Alignment) {
85     return allocate_buffer(Size, Alignment);
86   }
87 
88   // Pull in base class overloads.
89   using AllocatorBase<MallocAllocator>::Allocate;
90 
91   void Deallocate(const void *Ptr, size_t Size, size_t Alignment) {
92     deallocate_buffer(const_cast<void *>(Ptr), Size, Alignment);
93   }
94 
95   // Pull in base class overloads.
96   using AllocatorBase<MallocAllocator>::Deallocate;
97 
98   void PrintStats() const {}
99 };
100 
101 } // namespace llvm
102 
103 #endif // LLVM_SUPPORT_ALLOCATORBASE_H
104