Are there *any* circumstances that will implicitly allocate shared local memory?

[allanmac1]

I'm curious if there are any circumstances that will result in an implicit increase in a kernel workgroup's shared memory requirements?

For example, do the workgroup (or subgroup) functions like scan or reduce quietly "reserve" SLM?

If there are any circumstances where this might happen on SB, IVB, HSW or BDW then could you list them?

[Robert_I_Intel]

Allan,

The following functions do implicitly reserve SLM on BDW, since all of them are OpenCL 2.0 functions:

work_group_broadcast()

work_group_any()

work_group_all()

work_group_reduce<op>()

work_group_scan_inclusive<op>()

work_group_scan_exclusive<op>()

The amount of reserved local memory varies per function, for example broadcast / any / all require less local memory than reduce / scan.

We currently use implicit SLM in the implementation, but things could always change in the future.

[allanmac1]

Perfect, that makes sense.

I'll assume clGetKernelWorkGroupInfo(CL_KERNEL_LOCAL_MEM_SIZE) will properly report the extra SLM in use.

Thanks for the clarification.