Name

atomicCompSwap — perform an atomic compare-exchange operation to a variable

Declaration

int atomicCompSwap(inout int  mem,
 uint  compare,
 uint  data);
uint atomicCompSwap(inout uint  mem,
 uint  compare,
 uint  data);

Parameters

mem

The variable to use as the target of the operation.

data

The data to be compared and potentially exchanged with mem.

Description

atomicCompSwap performs an atomic comparison of compare with the contents of mem. If the content of mem is equal to compare, then the content of data is written into mem and is returned from the function. Otherwise, the original contents of mem are returned. The contents of the memory being updated by the atomic operation are guaranteed not to be modified by any other assignment or atomic memory function in any shader invocation between the time the original value is read and the time the new value is written.

Atomic memory functions are supported only for a limited set of variables. A shader will fail to compile if the value passed to the mem argument of an atomic memory function does not correspond to a buffer or shared variable. It is acceptable to pass an element of an array or a single component of a vector to the mem argument of an atomic memory function, as long as the underlying array or vector is a buffer or shared variable.

Version Support

FunctionVersion 1.10Version 1.20Version 1.30Version 1.40Version 1.50Version 3.30Version 4.00Version 4.10Version 4.20Version 4.30
atomicCompSwap---------Y

See Also

atomicAdd, atomicAnd, atomicOr, atomicXor, atomicMin, atomicMax, atomicExchange

Copyright

Copyright © 2011-2012 Khronos Group. This material may be distributed subject to the terms and conditions set forth in the Open Publication License, v 1.0, 8 June 1999. http://opencontent.org/openpub/.