paper update

docs/paper.tex

@@ -717,6 +717,17 @@ now give a summary of some of the limitations of Emscripten's approach.
       using normal JavaScript loops.
 \end{itemize}
 
+After seeing these limitations, it is worth noting that some advanced LLVM instructions turn out to be
+surprisingly easy to implement. For example, C++ exceptions are represented in
+LLVM by \emph{invoke} and \emph{unwind}, where \emph{invoke} is a call to a function that will
+potentially trigger an \emph{unwind}, and \emph{unwind} returns to the earliest invoke.
+If one were to implement those
+in a typical compiler, doing so would require careful work. In Emscripen, however,
+it is possible to do so using JavaScript exceptions in a straightforward manner:
+\emph{invoke} becomes a function call wrapped in a \emph{try} block, and \emph{unwind}
+becomes \emph{throw}. This is a case where compiling to a high-level language turns
+out to be quite convenient.
+
 \section{Emscripten's Architecture}
 \label{sec:emarch}