Shiro (HaP19)

[subroutine] Look at the top 3 cards of R&D and arrange them in any order.
[subroutine] The Runner accesses the top card of R&D unless the Corp pays 1 [Credits].

Does first subroutine refer to Corp or Runner?

Corp.

If a card does not specify Corp or Runner, it is giving instructions to the controlling player. Consider the difference between Archer (trash 1 program) and Burke Bugs (Trace0 - if successful, the Runner trashes 1 program).