\section{Optimizations}

  MLRISC assumes that all high level optimizations (target
  independent) have already been performed. This includes things like
  inlining, array dependence analysis, and array bounds check
  elimination.  The target dependent optimizations that remain include
  register allocation, scheduling and traditional optimizations to
  support scheduling. 

\subsection{Register allocation}
  
  MLRISC includes a state-of-the-art graph-coloring based register
  allocator that has an aggressive algorithm for copy-propagation. The
  latter guarantees to eliminate copy instructions without introducing
  spills.

   Spills in the register allocator are under the control of the
client via call-backs to the front end. Where to spill registers and
the associated information that must be maintained is client specific
and varies with the compiler. 

\subsection{Scheduling for Superscalar Architectures}
  Several algorithms for acyclic global scheduling are provided. These
include:

  \begin{itemize}
    \item Superblock,
    \item a variant of Bernstein/Rodeh, and
    \item Percolation based scheduling.
  \end{itemize}

These algorithms tend to be quite complex and require a large number
of support data structures and analysis. These include data structures
such as:

  \begin{itemize}
    \item dominator/post dominator trees,
    \item loop nesting tree,
    \item control dependency graphs, and 
    \item data dependency graphs.
 \end{itemize}

Support analysis and optimization include:

  \begin{itemize}
    \item constant propagation,
    \item global value numbering,
    \item global code motion, and
    \item loop invariant hoisting.
  \end{itemize}

\subsection{VLIW Compilation}
  MLRISC also contains a framework for the compilation of 
predicated VLIW architectures.
Currently, the following algorithms have been implemented.
  \begin{itemize} 
    \item hyperblock formation
    \item hyperblock scheduling
    \item modulo scheduling
  \end{itemize}