blob: d7d60371d315f0b52942fa73625b62cb961b8183 [file] [log] [blame]
//===- 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 <system_error>
namespace llvm {
// Forward declare raw_ostream: it is used for debug dumping below.
class raw_ostream;
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), AllocatedSize(0) {}
MemoryBlock(void *addr, size_t allocatedSize)
: Address(addr), AllocatedSize(allocatedSize) {}
void *base() const { return Address; }
/// The size as it was allocated. This is always greater or equal to the
/// size that was originally requested.
size_t allocatedSize() const { return AllocatedSize; }
void *Address; ///< Address of first byte of memory area
size_t AllocatedSize; ///< 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,
/// The \p MF_HUGE_HINT flag is used to indicate that the request for
/// a memory block should be satisfied with large pages if possible.
/// This is only a hint and small pages will be used as fallback.
/// The presence or absence of this flag in the returned memory block
/// is (at least currently) *not* a reliable indicator that the memory
/// block will use or will not use large pages. On some systems a request
/// without this flag can be backed by large pages without this flag being
/// set, and on some other systems a request with this flag can fallback
/// to small pages without this flag being cleared.
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.
/// 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() {
if (M.base())
void *base() const { return M.base(); }
/// The size as it was allocated. This is always greater or equal to the
/// size that was originally requested.
size_t allocatedSize() const { return M.allocatedSize(); }
MemoryBlock getMemoryBlock() const { return M; }
std::error_code release() {
std::error_code EC;
if (M.base()) {
EC = Memory::releaseMappedMemory(M);
M = MemoryBlock();
return EC;
MemoryBlock M;
#ifndef NDEBUG
/// Debugging output for Memory::ProtectionFlags.
raw_ostream &operator<<(raw_ostream &OS, const Memory::ProtectionFlags &PF);
/// Debugging output for MemoryBlock.
raw_ostream &operator<<(raw_ostream &OS, const MemoryBlock &MB);
#endif // ifndef NDEBUG
} // end namespace sys
} // end namespace llvm