See files in compiler/ with nx in their name.
VINSN means Virtual Instruction.
Those likely belong to the same category of SBCL's Virtual Operations (VOPs).
<- copy register @ label @= label (aligned) -> jump to label ^ branch ? register (unwired) $ register (wired)
LAP means Lisp Assembly Parser (probably). It's a DSL that compiles into opcodes.
(% x) register ($ x) immediate (@ x) memory operand; x ~ ([seg] [disp] [base] [index] [scale]) x labelref (:rcontext x) memory operand, using segment register or gpr; see @ for syntax of x. (:self fn) self-reference