Edit

_InterlockedCompareExchangePointer intrinsic functions

  • Article

Microsoft Specific

Performs an atomic operation that stores the Exchange address in the Destination address if the Comparand and the Destination address are equal.

Syntax

void * _InterlockedCompareExchangePointer (
   void * volatile * Destination,
   void * Exchange,
   void * Comparand
);
void * _InterlockedCompareExchangePointer_acq (
   void * volatile * Destination,
   void * Exchange,
   void * Comparand
);
void * _InterlockedCompareExchangePointer_HLEAcquire (
   void * volatile * Destination,
   void * Exchange,
   void * Comparand
);
void * _InterlockedCompareExchangePointer_HLERelease (
   void * volatile * Destination,
   void * Exchange,
   void * Comparand
);
void * _InterlockedCompareExchangePointer_nf (
   void * volatile * Destination,
   void * Exchange,
   void * Comparand
);
void * _InterlockedCompareExchangePointer_np (
   void * volatile * Destination,
   void * Exchange,
   void * Comparand
);
void * _InterlockedCompareExchangePointer_rel (
   void * volatile * Destination,
   void * Exchange,
   void * Comparand
);

Parameters

Destination
[in, out] Pointer to a pointer to the destination value. The sign is ignored.

Exchange
[in] Exchange pointer. The sign is ignored.

Comparand
[in] Pointer to compare to destination. The sign is ignored.

Return value

The return value is the initial value of the destination.

Requirements

Intrinsic Architecture Header
_InterlockedCompareExchangePointer x86, ARM, x64, ARM64 <intrin.h>
_InterlockedCompareExchangePointer_acq, _InterlockedCompareExchangePointer_nf, _InterlockedCompareExchangePointer_rel ARM, ARM64 <iiintrin.h>
_InterlockedCompareExchangePointer_HLEAcquire, _InterlockedCompareExchangePointer_HLERelease x86, x64 <immintrin.h>

Remarks

_InterlockedCompareExchangePointer performs an atomic comparison of the Destination address with the Comparand address. If the Destination address is equal to the Comparand address, the Exchange address is stored in the address specified by Destination. Otherwise, no operation is performed.

_InterlockedCompareExchangePointer provides compiler intrinsic support for the Win32 Windows SDK InterlockedCompareExchangePointer function.

For an example of how to use _InterlockedCompareExchangePointer, see _InterlockedDecrement.

On ARM platforms, use the intrinsics with _acq and _rel suffixes if you need acquire and release semantics, such as at the beginning and end of a critical section. ARM intrinsics with an _nf ("no fence") suffix don't act as a memory barrier.

The intrinsics with an _np ("no prefetch") suffix prevent a possible prefetch operation from being inserted by the compiler.

On Intel platforms that support Hardware Lock Elision (HLE) instructions, the intrinsics with _HLEAcquire and _HLERelease suffixes include a hint to the processor that can accelerate performance by eliminating a lock write step in hardware. If these intrinsics are called on platforms that don't support HLE, the hint is ignored.

These routines are only available as intrinsics.

END Microsoft Specific

See also

Compiler intrinsics
Keywords