InterlockedCompareExchange function (HLSL reference)

Atomically compares the destination with the comparison value. If they are identical, the destination is overwritten with the input value. The original value is set to the destination's original value.


void InterlockedCompareExchange(
  in  R dest,
  in  T compare_value,
  in  T value,
  out T original_value


dest [in]

Type: R

The destination address.

compare_value [in]

Type: T

The comparison value.

value [in]

Type: T

The input value.

original_value [out]

Type: T

The original value.

Return value

This function does not return a value.


Atomically compares the value referenced by dest with compare_value, stores value in the location referenced by dest if the values match, returns the original value of dest in original_value. This operation can only be performed on int or uint typed resources and shared memory variables. There are two possible uses for this function. The first is when R is a shared memory variable type. In this case, the function performs the operation on the shared memory register referenced by dest. The second scenario is when R is a resource variable type. In this scenario, the function performs the operation on the resource location referenced by dest. This operation is only available when R is readable and writable.


If you call InterlockedCompareExchange in a for or while compute shader loop, to properly compile, you must use the [allow_uav_condition] attribute on that loop.


Minimum Shader Model

This function is supported in the following shader models.

Shader Model Supported
Shader Model 5 and higher shader models yes


This function is supported in the following types of shaders:

Vertex Hull Domain Geometry Pixel Compute
x x x x x x


See also

Intrinsic Functions

Shader Model 5