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//===- llvm/Support/Memory.h - Memory Support -------------------*- C++ -*-===//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
// This file declares the llvm::sys::Memory class.
#include "llvm/Support/DataTypes.h"
#include <string>
#include <system_error>
namespace llvm {
namespace sys {
/// This class encapsulates the notion of a memory block which has an address
/// and a size. It is used by the Memory class (a friend) as the result of
/// various memory allocation operations.
/// @see Memory
/// Memory block abstraction.
class MemoryBlock {
MemoryBlock() : Address(nullptr), Size(0) { }
MemoryBlock(void *addr, size_t size) : Address(addr), Size(size) { }
void *base() const { return Address; }
size_t size() const { return Size; }
void *Address; ///< Address of first byte of memory area
size_t Size; ///< Size, in bytes of the memory area
unsigned Flags = 0;
friend class Memory;
/// This class provides various memory handling functions that manipulate
/// MemoryBlock instances.
/// @since 1.4
/// An abstraction for memory operations.
class Memory {
enum ProtectionFlags {
MF_READ = 0x1000000,
MF_WRITE = 0x2000000,
MF_EXEC = 0x4000000,
MF_RWE_MASK = 0x7000000,
MF_HUGE_HINT = 0x0000001
/// This method allocates a block of memory that is suitable for loading
/// dynamically generated code (e.g. JIT). An attempt to allocate
/// \p NumBytes bytes of virtual memory is made.
/// \p NearBlock may point to an existing allocation in which case
/// an attempt is made to allocate more memory near the existing block.
/// The actual allocated address is not guaranteed to be near the requested
/// address.
/// \p Flags is used to set the initial protection flags for the block
/// of the memory.
/// \p EC [out] returns an object describing any error that occurs.
/// This method may allocate more than the number of bytes requested. The
/// actual number of bytes allocated is indicated in the returned
/// MemoryBlock.
/// The start of the allocated block must be aligned with the
/// system allocation granularity (64K on Windows, page size on Linux).
/// If the address following \p NearBlock is not so aligned, it will be
/// rounded up to the next allocation granularity boundary.
/// \r a non-null MemoryBlock if the function was successful,
/// otherwise a null MemoryBlock is with \p EC describing the error.
/// Allocate mapped memory.
static MemoryBlock allocateMappedMemory(size_t NumBytes,
const MemoryBlock *const NearBlock,
unsigned Flags,
std::error_code &EC);
/// This method releases a block of memory that was allocated with the
/// allocateMappedMemory method. It should not be used to release any
/// memory block allocated any other way.
/// \p Block describes the memory to be released.
/// \r error_success if the function was successful, or an error_code
/// describing the failure if an error occurred.
/// Release mapped memory.
static std::error_code releaseMappedMemory(MemoryBlock &Block);
/// This method sets the protection flags for a block of memory to the
/// state specified by /p Flags. The behavior is not specified if the
/// memory was not allocated using the allocateMappedMemory method.
/// \p Block describes the memory block to be protected.
/// \p Flags specifies the new protection state to be assigned to the block.
/// \p ErrMsg [out] returns a string describing any error that occurred.
/// If \p Flags is MF_WRITE, the actual behavior varies
/// with the operating system (i.e. MF_READ | MF_WRITE on Windows) and the
/// target architecture (i.e. MF_WRITE -> MF_READ | MF_WRITE on i386).
/// \r error_success if the function was successful, or an error_code
/// describing the failure if an error occurred.
/// Set memory protection state.
static std::error_code protectMappedMemory(const MemoryBlock &Block,
unsigned Flags);
/// InvalidateInstructionCache - Before the JIT can run a block of code
/// that has been emitted it must invalidate the instruction cache on some
/// platforms.
static void InvalidateInstructionCache(const void *Addr, size_t Len);
/// Owning version of MemoryBlock.
class OwningMemoryBlock {
OwningMemoryBlock() = default;
explicit OwningMemoryBlock(MemoryBlock M) : M(M) {}
OwningMemoryBlock(OwningMemoryBlock &&Other) {
M = Other.M;
Other.M = MemoryBlock();
OwningMemoryBlock& operator=(OwningMemoryBlock &&Other) {
M = Other.M;
Other.M = MemoryBlock();
return *this;
~OwningMemoryBlock() {
void *base() const { return M.base(); }
size_t size() const { return M.size(); }
MemoryBlock getMemoryBlock() const { return M; }
MemoryBlock M;