call ddc#custom#patch_global('sources', ['registers-words'])
call ddc#custom#patch_global('sourceOptions', {
    \ 'registers-words': {
    \   'mark': 'R',
    \ }})
call ddc#custom#patch_global('sourceParams', {
    \ 'registers-words': {
    \   'registers': '/"012',
    \ }})