vendor/edk2/7babb4372e6a34cbbc54249b25056272a5a9924c

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diff --git a/MdePkg/Library/BaseSynchronizationLib/Arm/Synchronization.asm b/MdePkg/Library/BaseSynchronizationLib/Arm/Synchronization.asm
new file mode 100644
index 000000000000..fac8794971ef
--- /dev/null
+++ b/MdePkg/Library/BaseSynchronizationLib/Arm/Synchronization.asm
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+//  Implementation of synchronization functions for ARM architecture
+//
+//  Copyright (c) 2012-2015, ARM Limited. All rights reserved.
+//  Copyright (c) 2015, Linaro Limited. All rights reserved.
+//
+//  This program and the accompanying materials
+//  are licensed and made available under the terms and conditions of the BSD License
+//  which accompanies this distribution.  The full text of the license may be found at
+//  http://opensource.org/licenses/bsd-license.php
+//
+//  THE PROGRAM IS DISTRIBUTED UNDER THE BSD LICENSE ON AN "AS IS" BASIS,
+//  WITHOUT WARRANTIES OR REPRESENTATIONS OF ANY KIND, EITHER EXPRESS OR IMPLIED.
+//
+//
+
+    EXPORT  InternalSyncCompareExchange16
+    EXPORT  InternalSyncCompareExchange32
+    EXPORT  InternalSyncCompareExchange64
+    EXPORT  InternalSyncIncrement
+    EXPORT  InternalSyncDecrement
+
+    AREA   ArmSynchronization, CODE, READONLY
+
+/**
+  Performs an atomic compare exchange operation on a 16-bit unsigned integer.
+
+  Performs an atomic compare exchange operation on the 16-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 16-bit value for the compare exchange
+                        operation.
+  @param  CompareValue  16-bit value used in compare operation.
+  @param  ExchangeValue 16-bit value used in exchange operation.
+
+  @return The original *Value before exchange.
+
+**/
+//UINT16
+//EFIAPI
+//InternalSyncCompareExchange16 (
+//  IN      volatile UINT16           *Value,
+//  IN      UINT16                    CompareValue,
+//  IN      UINT16                    ExchangeValue
+//  )
+InternalSyncCompareExchange16
+  dmb
+
+InternalSyncCompareExchange16Again
+  ldrexh  r3, [r0]
+  cmp     r3, r1
+  bne     InternalSyncCompareExchange16Fail
+
+InternalSyncCompareExchange16Exchange
+  strexh  ip, r2, [r0]
+  cmp     ip, #0
+  bne     InternalSyncCompareExchange16Again
+
+InternalSyncCompareExchange16Fail
+  dmb
+  mov     r0, r3
+  bx      lr
+
+/**
+  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
+//  )
+InternalSyncCompareExchange32
+  dmb
+
+InternalSyncCompareExchange32Again
+  ldrex   r3, [r0]
+  cmp     r3, r1
+  bne     InternalSyncCompareExchange32Fail
+
+InternalSyncCompareExchange32Exchange
+  strex   ip, r2, [r0]
+  cmp     ip, #0
+  bne     InternalSyncCompareExchange32Again
+
+InternalSyncCompareExchange32Fail
+  dmb
+  mov     r0, r3
+  bx      lr
+
+/**
+  Performs an atomic compare exchange operation on a 64-bit unsigned integer.
+
+  Performs an atomic compare exchange operation on the 64-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 64-bit value for the compare exchange
+                        operation.
+  @param  CompareValue  64-bit value used in compare operation.
+  @param  ExchangeValue 64-bit value used in exchange operation.
+
+  @return The original *Value before exchange.
+
+**/
+//UINT64
+//EFIAPI
+//InternalSyncCompareExchange64 (
+//  IN      volatile UINT64           *Value,         // r0
+//  IN      UINT64                    CompareValue,   // r2-r3
+//  IN      UINT64                    ExchangeValue   // stack
+//  )
+InternalSyncCompareExchange64
+  push    { r4-r7 }
+  ldrd    r4, r5, [sp, #16]
+  dmb
+
+InternalSyncCompareExchange64Again
+  ldrexd  r6, r7, [r0]
+  cmp     r6, r2
+  cmpeq   r7, r3
+  bne     InternalSyncCompareExchange64Fail
+
+InternalSyncCompareExchange64Exchange
+  strexd  ip, r4, r5, [r0]
+  cmp     ip, #0
+  bne     InternalSyncCompareExchange64Again
+
+InternalSyncCompareExchange64Fail
+  dmb
+  mov     r0, r6
+  mov     r1, r7
+  pop     { r4-r7 }
+  bx      lr
+
+/**
+  Performs an atomic increment of an 32-bit unsigned integer.
+
+  Performs an atomic increment of the 32-bit unsigned integer specified by
+  Value and returns the incremented value. The increment operation must be
+  performed using MP safe mechanisms. The state of the return value is not
+  guaranteed to be MP safe.
+
+  @param  Value A pointer to the 32-bit value to increment.
+
+  @return The incremented value.
+
+**/
+//UINT32
+//EFIAPI
+//InternalSyncIncrement (
+//  IN      volatile UINT32           *Value
+//  )
+InternalSyncIncrement
+  dmb
+TryInternalSyncIncrement
+  ldrex   r1, [r0]
+  add     r1, r1, #1
+  strex   r2, r1, [r0]
+  cmp     r2, #0
+  bne     TryInternalSyncIncrement
+  dmb
+  mov     r0, r1
+  bx      lr
+
+/**
+  Performs an atomic decrement of an 32-bit unsigned integer.
+
+  Performs an atomic decrement of the 32-bit unsigned integer specified by
+  Value and returns the decrement value. The decrement operation must be
+  performed using MP safe mechanisms. The state of the return value is not
+  guaranteed to be MP safe.
+
+  @param  Value A pointer to the 32-bit value to decrement.
+
+  @return The decrement value.
+
+**/
+//UINT32
+//EFIAPI
+//InternalSyncDecrement (
+//  IN      volatile UINT32           *Value
+//  )
+InternalSyncDecrement
+  dmb
+TryInternalSyncDecrement
+  ldrex   r1, [r0]
+  sub     r1, r1, #1
+  strex   r2, r1, [r0]
+  cmp     r2, #0
+  bne     TryInternalSyncDecrement
+  dmb
+  mov     r0, r1
+  bx      lr
+
+  END