  Irksome is a library based on the Unified Form Language (UFL) that enables
automated generation of Runge--Kutta methods for time-stepping finite element
spatial discretizations of partial differential equations (PDE). Allowing users
to express semidiscrete forms of PDE, it generates UFL representations for the
stage-coupled variational problems to be solved at each time step. The
Firedrake package then generates efficient code for evaluating these
variational problems and allows users a wide range of options to deploy
efficient algebraic solvers in PETSc.
  In this paper, we describe several recent advances in Irksome. These include
alternate formulations of the Runge--Kutta time-stepping methods and optimized
support for diagonally implicit (DIRK) methods. Additionally, we present new
and improved tools for building preconditioners for the resulting linear and
linearized systems, demonstrating that these can lead to efficient approaches
for solving fully implicit Runge-Kutta discretizations.
  The new features are demonstrated through a sequence of computational
examples demonstrating the high-level interface and obtained solver
performance.
