AMD GCN Function Attributes#

These function attributes are supported by the AMD GCN back end:

amdgpu_hsa_kernel#

This attribute indicates that the corresponding function should be compiled as a kernel function, that is an entry point that can be invoked from the host via the HSA runtime library. By default functions are only callable only from other GCN functions.

This attribute is implicitly applied to any function named main, using default parameters.

Kernel functions may return an integer value, which will be written to a conventional place within the HSA “kernargs” region.

The attribute parameters configure what values are passed into the kernel function by the GPU drivers, via the initial register state. Some values are used by the compiler, and therefore forced on. Enabling other options may break assumptions in the compiler and/or run-time libraries.

private_segment_buffer: Set enable_sgpr_private_segment_buffer flag. Always on (required to locate the stack).
dispatch_ptr: Set enable_sgpr_dispatch_ptr flag. Always on (required to locate the launch dimensions).
queue_ptr: Set enable_sgpr_queue_ptr flag. Always on (required to convert address spaces).
kernarg_segment_ptr: Set enable_sgpr_kernarg_segment_ptr flag. Always on (required to locate the kernel arguments, “kernargs”).
dispatch_id: Set enable_sgpr_dispatch_id flag.
flat_scratch_init: Set enable_sgpr_flat_scratch_init flag.
private_segment_size: Set enable_sgpr_private_segment_size flag.
grid_workgroup_count_X: Set enable_sgpr_grid_workgroup_count_x flag. Always on (required to use OpenACC/OpenMP).
grid_workgroup_count_Y: Set enable_sgpr_grid_workgroup_count_y flag.
grid_workgroup_count_Z: Set enable_sgpr_grid_workgroup_count_z flag.
workgroup_id_X: Set enable_sgpr_workgroup_id_x flag.
workgroup_id_Y: Set enable_sgpr_workgroup_id_y flag.
workgroup_id_Z: Set enable_sgpr_workgroup_id_z flag.
workgroup_info: Set enable_sgpr_workgroup_info flag.
private_segment_wave_offset: Set enable_sgpr_private_segment_wave_byte_offset flag. Always on (required to locate the stack).
work_item_id_X: Set enable_vgpr_workitem_id parameter. Always on (can’t be disabled).
work_item_id_Y: Set enable_vgpr_workitem_id parameter. Always on (required to enable vectorization.)
work_item_id_Z: Set enable_vgpr_workitem_id parameter. Always on (required to use OpenACC/OpenMP).