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barrier — synchronize execution of multiple shader invocations


void barrier( void);


Available only in the Tessellation Control and Compute Shaders, barrier provides a partially defined order of execution between shader invocations. For any given static instance of barrier, in a tessellation control shader, all invocations for a single input patch must enter it before any will be allowed to continue beyond it. For any given static instance of barrier in a compute shader, all invocations within a single work group must enter it before any are allowed to continue beyond it. This ensures that values written by one invocation prior to a given static instance of barrier can be safely read by other invocations after their call to the same static instance of barrier. Because invocations may execute in undefined order between these barrier calls, the values of a per-vertex or per-patch output variable, or any shared variable will be undefined in a number of cases.

barrier may only be placed inside the function main() of the tessellation control shader, but may be placed anywhere in a compute shader. Calls to barrier may not be placed within any control flow. Barriers are also disallowed after a return statement in the function main().

Version Support

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
barrier - - - - - -
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