MdePkg/Library/BaseSynchronizationLib/Ia32/InterlockedCompareExchange32.c


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/** @file
  InterlockedCompareExchange32 function

  Copyright (c) 2006 - 2016, Intel Corporation. All rights reserved.<BR>
  SPDX-License-Identifier: BSD-2-Clause-Patent

**/


/**
  Performs an atomic compare exchange operation on a 32-bit unsigned integer.

  Performs an atomic compare exchange operation on the 32-bit unsigned integer
  specified by Value.  If Value is equal to CompareValue, then Value is set to
  ExchangeValue and CompareValue is returned.  If Value is not equal to CompareValue,
  then Value is returned.  The compare exchange operation must be performed using
  MP safe mechanisms.

  @param  Value         A pointer to the 32-bit value for the compare exchange
                        operation.
  @param  CompareValue  32-bit value used in compare operation.
  @param  ExchangeValue 32-bit value used in exchange operation.

  @return The original *Value before exchange.

**/
UINT32
EFIAPI
InternalSyncCompareExchange32 (
  IN      volatile UINT32           *Value,
  IN      UINT32                    CompareValue,
  IN      UINT32                    ExchangeValue
  )
{
  _asm {
    mov     ecx, Value
    mov     eax, CompareValue
    mov     edx, ExchangeValue
    lock    cmpxchg [ecx], edx
  }
}