atomicCompSwap(3) perform an atomic compare-exchange operation to a variable


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



The variable to use as the target of the operation.


The data to be compared and potentially exchanged with mem.


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, otherwise the content of mem is unmodifed. The function returns the original content of mem regardless of the outcome of the comparison. 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.


OpenGL Shading Language Version
Function Name 1.10 1.20 1.30 1.40 1.50 3.30 4.00 4.10 4.20 4.30 4.40 4.50
atomicCompSwap - - - - - - - - -


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