work_group_barrier

All work-items in a work-group executing the kernel on a processor must execute this function before any are allowed to continue execution beyond the work_group_barrier.

void work_group_barrier ( cl_mem_fence_flags flags)
void work_group_barrier ( cl_mem_fence_flags flags,
  memory_scope scope )

Description

The built-in function barrier has been renamed work_group_barrier. For backward compatibility, barrier is also supported.

All work-items in a work-group executing the kernel on a processor must execute this function before any are allowed to continue execution beyond the work_group_barrier. This function must be encountered by all work-items in a work-group executing the kernel. These rules apply to ND-ranges implemented with uniform and non-uniform work-groups.

If work_group_barrier is inside a conditional statement, then all work-items must enter the conditional if any work-item enters the conditional statement and executes the work_group_barrier.

If work_group_barrier is inside a loop, all work-items must execute the work_group_barrier for each iteration of the loop before any are allowed to continue execution beyond the work_group_barrier.

The work_group_barrier function also supports a variant that specifies the memory scope. For the work_group_barrier variant that does not take a memory scope, the scope is memory_scope_work_group.

The scope argument specifies whether the memory accesses of work-items in the work-group to memory address space(s) identified by flags become visible to all work-items in the work-group, the device or all SVM devices.

The work_group_barrier function can also be used to specify which memory operations i.e. to global memory, local memory or images become visible to the appropriate memory scope identified by scope. The flags argument specifies the memory address spaces and can be set to 0 or a combination of the following values ORed together. When these flags are OR’ed together the work_group_barrier acts as a combined barrier for all address spaces specified by the flags ordering memory accesses both within and across the specified address spaces.

CLK_LOCAL_MEM_FENCE - The work_group_barrier function will ensure that all local memory accesses become visible to all workitems in the work-group. Note that the value of scope is ignored as the memory scope is always memory_scope_work_group.

CLK_GLOBAL_MEM_FENCE – The work_group_barrier function ensure that all global memory accesses become visible to the appropriate scope as given by scope.

CLK_IMAGE_MEM_FENCE – The work_group_barrier function will ensure that all image memory accesses become visible to the appropriate scope as given by scope. The value of scope must be memory_scope_work_group or memory_scope_device.

Specification

OpenCL Specification

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