from Imagemagick sources..

https://github.com/ImageMagick/dcraw/commit/00d7d612efb84e27e465a7fbeca355e9a7605258

but you can try latest (dcraw 9.28) commit from this repo.. 

in theory it might make cingg's raw decoding a bit faster on opencl-capable gpu... 

only performace claim I found was

"With an OpenCL version of dcraw.c converting an 6034x4012 NEF file to JPEG takes 4.7 seconds instead of 13.8 seconds on my machine.
1:05 AM · 25 мая 2016 г.·" - https://mobile.twitter.com/MagickNET/status/735230384615661568