[wpiutil] Reduce llvm collections patches (#4268)

wpiutil/src/main/native/include/wpi/AllocatorBase.h

@@ -0,0 +1,103 @@
+//===- AllocatorBase.h - Simple memory allocation abstraction ---*- C++ -*-===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+/// \file
+///
+/// This file defines MallocAllocator. MallocAllocator conforms to the LLVM
+/// "Allocator" concept which consists of an Allocate method accepting a size
+/// and alignment, and a Deallocate accepting a pointer and size. Further, the
+/// LLVM "Allocator" concept has overloads of Allocate and Deallocate for
+/// setting size and alignment based on the final type. These overloads are
+/// typically provided by a base class template \c AllocatorBase.
+///
+//===----------------------------------------------------------------------===//
+
+#ifndef WPIUTIL_WPI_ALLOCATORBASE_H
+#define WPIUTIL_WPI_ALLOCATORBASE_H
+
+#include "wpi/Compiler.h"
+#include "wpi/MemAlloc.h"
+
+namespace wpi {
+
+/// CRTP base class providing obvious overloads for the core \c
+/// Allocate() methods of LLVM-style allocators.
+///
+/// This base class both documents the full public interface exposed by all
+/// LLVM-style allocators, and redirects all of the overloads to a single core
+/// set of methods which the derived class must define.
+template <typename DerivedT> class AllocatorBase {
+public:
+  /// Allocate \a Size bytes of \a Alignment aligned memory. This method
+  /// must be implemented by \c DerivedT.
+  void *Allocate(size_t Size, size_t Alignment) {
+#ifdef __clang__
+    static_assert(static_cast<void *(AllocatorBase::*)(size_t, size_t)>(
+                      &AllocatorBase::Allocate) !=
+                      static_cast<void *(DerivedT::*)(size_t, size_t)>(
+                          &DerivedT::Allocate),
+                  "Class derives from AllocatorBase without implementing the "
+                  "core Allocate(size_t, size_t) overload!");
+#endif
+    return static_cast<DerivedT *>(this)->Allocate(Size, Alignment);
+  }
+
+  /// Deallocate \a Ptr to \a Size bytes of memory allocated by this
+  /// allocator.
+  void Deallocate(const void *Ptr, size_t Size, size_t Alignment) {
+#ifdef __clang__
+    static_assert(
+        static_cast<void (AllocatorBase::*)(const void *, size_t, size_t)>(
+            &AllocatorBase::Deallocate) !=
+            static_cast<void (DerivedT::*)(const void *, size_t, size_t)>(
+                &DerivedT::Deallocate),
+        "Class derives from AllocatorBase without implementing the "
+        "core Deallocate(void *) overload!");
+#endif
+    return static_cast<DerivedT *>(this)->Deallocate(Ptr, Size, Alignment);
+  }
+
+  // The rest of these methods are helpers that redirect to one of the above
+  // core methods.
+
+  /// Allocate space for a sequence of objects without constructing them.
+  template <typename T> T *Allocate(size_t Num = 1) {
+    return static_cast<T *>(Allocate(Num * sizeof(T), alignof(T)));
+  }
+
+  /// Deallocate space for a sequence of objects without constructing them.
+  template <typename T>
+  std::enable_if_t<!std::is_same<std::remove_cv_t<T>, void>::value, void>
+  Deallocate(T *Ptr, size_t Num = 1) {
+    Deallocate(static_cast<const void *>(Ptr), Num * sizeof(T), alignof(T));
+  }
+};
+
+class MallocAllocator : public AllocatorBase<MallocAllocator> {
+public:
+  void Reset() {}
+
+  LLVM_ATTRIBUTE_RETURNS_NONNULL void *Allocate(size_t Size, size_t Alignment) {
+    return allocate_buffer(Size, Alignment);
+  }
+
+  // Pull in base class overloads.
+  using AllocatorBase<MallocAllocator>::Allocate;
+
+  void Deallocate(const void *Ptr, size_t Size, size_t Alignment) {
+    deallocate_buffer(const_cast<void *>(Ptr), Size, Alignment);
+  }
+
+  // Pull in base class overloads.
+  using AllocatorBase<MallocAllocator>::Deallocate;
+
+  void PrintStats() const {}
+};
+
+} // namespace wpi
+
+#endif // WPIUTIL_WPI_ALLOCATORBASE_H