Fix broken implementation of firstbit family of opcodes
Fix broken implementation of firstbit family of opcodes

adrianbu/renderdoc,Lssikkes/renderdoc,TurtleRockStudios/renderdoc_public,Lssikkes/renderdoc,adrianbu/renderdoc,Anteru/renderdoc,Velro/renderdoc,TurtleRockStudios/renderdoc_public,baldurk/renderdoc,moradin/renderdoc,etnlGD/renderdoc,TurtleRockStudios/renderdoc_public,Velro/renderdoc,Yours3lf/renderdoc,Yours3lf/renderdoc,victor-moya/renderdoc,etnlGD/renderdoc,etnlGD/renderdoc,victor-moya/renderdoc,moradin/renderdoc,googlestadia/renderdoc,victor-moya/renderdoc,moradin/renderdoc,Zorro666/renderdoc,Velro/renderdoc,cgmb/renderdoc,TurtleRockStudios/renderdoc_public,Velro/renderdoc,Zorro666/renderdoc,etnlGD/renderdoc,googlestadia/renderdoc,victor-moya/renderdoc,cgmb/renderdoc,Lssikkes/renderdoc,Anteru/renderdoc,Lssikkes/renderdoc,baldurk/renderdoc,Velro/renderdoc,moradin/renderdoc,TurtleRockStudios/renderdoc_public,Lssikkes/renderdoc,adrianbu/renderdoc,Zorro666/renderdoc,michaelrgb/renderdoc,cgmb/renderdoc,victor-moya/renderdoc,moradin/renderdoc,Yours3lf/renderdoc,Yours3lf/renderdoc,etnlGD/renderdoc,cgmb/renderdoc,googlestadia/renderdoc,baldurk/renderdoc,michaelrgb/renderdoc,googlestadia/renderdoc,Zorro666/renderdoc,baldurk/renderdoc,cgmb/renderdoc,adrianbu/renderdoc,Anteru/renderdoc,moradin/renderdoc,Velro/renderdoc,Anteru/renderdoc,Anteru/renderdoc,Zorro666/renderdoc,michaelrgb/renderdoc,adrianbu/renderdoc,TurtleRockStudios/renderdoc_public,michaelrgb/renderdoc,michaelrgb/renderdoc,baldurk/renderdoc,baldurk/renderdoc,victor-moya/renderdoc,Anteru/renderdoc,Yours3lf/renderdoc,adrianbu/renderdoc,googlestadia/renderdoc,etnlGD/renderdoc,Anteru/renderdoc,Zorro666/renderdoc,Yours3lf/renderdoc,Lssikkes/renderdoc,googlestadia/renderdoc