* If :ref:`glc<amdgpu_synid_glc>` is specified, gets the memory value before the operation.
*Size:* depends on :ref:`dmask<amdgpu_synid_dmask>` and :ref:`tfe<amdgpu_synid_tfe>`:
*:ref:`dmask<amdgpu_synid_dmask>` may specify 1 data element for 32-bit-per-pixel surfaces or 2 data elements for 64-bit-per-pixel surfaces. Each data element occupies 1 dword.
*:ref:`tfe<amdgpu_synid_tfe>` adds 1 dword if specified.