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   2   Copyright 1988-2022 Free Software Foundation, Inc.
   3   This is part of the GCC manual.
   4   For copying conditions, see the copyright.rst file.
   5
   6 .. _amd-gcn-function-attributes:
   7
   8 AMD GCN Function Attributes
   9 ^^^^^^^^^^^^^^^^^^^^^^^^^^^
  10
  11 These function attributes are supported by the AMD GCN back end:
  12
  13 .. index:: amdgpu_hsa_kernel function attribute, AMD GCN
  14
  15 .. amd-gcn-fn-attr:: amdgpu_hsa_kernel
  16
  17   This attribute indicates that the corresponding function should be compiled as
  18   a kernel function, that is an entry point that can be invoked from the host
  19   via the HSA runtime library.  By default functions are only callable only from
  20   other GCN functions.
  21
  22   This attribute is implicitly applied to any function named ``main``, using
  23   default parameters.
  24
  25   Kernel functions may return an integer value, which will be written to a
  26   conventional place within the HSA "kernargs" region.
  27
  28   The attribute parameters configure what values are passed into the kernel
  29   function by the GPU drivers, via the initial register state.  Some values are
  30   used by the compiler, and therefore forced on.  Enabling other options may
  31   break assumptions in the compiler and/or run-time libraries.
  32
  33   ``private_segment_buffer``
  34     Set ``enable_sgpr_private_segment_buffer`` flag.  Always on (required to
  35     locate the stack).
  36
  37   ``dispatch_ptr``
  38     Set ``enable_sgpr_dispatch_ptr`` flag.  Always on (required to locate the
  39     launch dimensions).
  40
  41   ``queue_ptr``
  42     Set ``enable_sgpr_queue_ptr`` flag.  Always on (required to convert address
  43     spaces).
  44
  45   ``kernarg_segment_ptr``
  46     Set ``enable_sgpr_kernarg_segment_ptr`` flag.  Always on (required to
  47     locate the kernel arguments, "kernargs").
  48
  49   ``dispatch_id``
  50     Set ``enable_sgpr_dispatch_id`` flag.
  51
  52   ``flat_scratch_init``
  53     Set ``enable_sgpr_flat_scratch_init`` flag.
  54
  55   ``private_segment_size``
  56     Set ``enable_sgpr_private_segment_size`` flag.
  57
  58   ``grid_workgroup_count_X``
  59     Set ``enable_sgpr_grid_workgroup_count_x`` flag.  Always on (required to
  60     use OpenACC/OpenMP).
  61
  62   ``grid_workgroup_count_Y``
  63     Set ``enable_sgpr_grid_workgroup_count_y`` flag.
  64
  65   ``grid_workgroup_count_Z``
  66     Set ``enable_sgpr_grid_workgroup_count_z`` flag.
  67
  68   ``workgroup_id_X``
  69     Set ``enable_sgpr_workgroup_id_x`` flag.
  70
  71   ``workgroup_id_Y``
  72     Set ``enable_sgpr_workgroup_id_y`` flag.
  73
  74   ``workgroup_id_Z``
  75     Set ``enable_sgpr_workgroup_id_z`` flag.
  76
  77   ``workgroup_info``
  78     Set ``enable_sgpr_workgroup_info`` flag.
  79
  80   ``private_segment_wave_offset``
  81     Set ``enable_sgpr_private_segment_wave_byte_offset`` flag.  Always on
  82     (required to locate the stack).
  83
  84   ``work_item_id_X``
  85     Set ``enable_vgpr_workitem_id`` parameter.  Always on (can't be disabled).
  86
  87   ``work_item_id_Y``
  88     Set ``enable_vgpr_workitem_id`` parameter.  Always on (required to enable
  89     vectorization.)
  90
  91   ``work_item_id_Z``
  92     Set ``enable_vgpr_workitem_id`` parameter.  Always on (required to use
  93     OpenACC/OpenMP).