Subversion Repositories QNX 8.QNX8 LLVM/Clang compiler suite

//===- llvm/Support/Memory.h - Memory Support -------------------*- 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

//

//===----------------------------------------------------------------------===//

//

// This file declares the llvm::sys::Memory class.

//

//===----------------------------------------------------------------------===//

#ifndef LLVM_SUPPORT_MEMORY_H

#define LLVM_SUPPORT_MEMORY_H

#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 {

  public:

    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; }

  private:

    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 {

  public:

    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 {

  public:

    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())

        Memory::releaseMappedMemory(M);

    }

    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;

    }

  private:

    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

#endif