\section{Contributions} The optimizations provided by MLRISC are at a similar level to those performed by the Impact compiler; several target back ends exist (Dec Alpha, HPPA, Sparc, x86, and PPC); but more importantly, the framework has been demonstrated in \href{systems.html}{real use} for languages with radically different execution models. These include: \begin{center} \begin{tabular}{|c|c|} \hline Compiler & Association \\ \hline \begin{color}{#005500}SML/NJ\end{color} & Bell Labs and Princeton\\\hline \begin{color}{#005500}TIL\end{color} & CMU \\ \hline \begin{color}{#005500}Tiger\end{color} & Princeton \\ \hline \begin{color}{#005500}C--\end{color} & OGI \\ \hline \begin{color}{#005500}SML/Regions\end{color} & DIKU \\ \hline \begin{color}{#005500}Moby\end{color} & Bell Labs \\ \hline \end{tabular} \end{center} The strength of MLRISC lies in the ability to easily create high quality code generator for each of these systems. For example: \begin{description} \item[Tiger:] Has an execution model very similar to C with stack allocated activation frames, and also maintains static and dynamic chains to support lexical scoping. \item[TIL:] Is similar to C in its use of activation frames, however it uses a \emph{typed intermediate language} that supports \emph{almost tag-free} garbage collection. This has severe implications on the interaction of spilling and garbage collection. The set of live variables and their locations, be it registers or frame slots, is recorded in a trace table for a specific program point. When spilling occurs, it is necessary to adjust some of these trace tables to reflect the new locations of live variables. \item[SML/NJ:] Has no runtime stack, but stores all execution context in a garbage collected heap. This arrangement imposes special requirements for spilling registers. SML/NJ also does \emph{dynamic linking} --- that is to say, no use is made of a conventional linker, but machine code is generated directly and linked into the interactive environment, dynamically. \item[C--:] Is a C-like portable assembly language used as an intermediate language for high level typed language, and provides direct compilation support for exceptions and precise garbage collection. In addition, it allows interoperability with C function calls. \end{description} It is not uncommon for any of these systems to store special global values in dedicated registers, and use their own parameter passing and callee-save conventions. In any language that supports garbage collection, there are also the issues of generating gc type maps, and gc-safety in aggressive optimizations. MLRISC deals with all these important issues by allowing customization of many aspects of the system.