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\subsection{Description}
The main component of the artifact is an interactive VM called \tinyvm\ built on top of the LLVM MCJIT runtime environment and the \osrkit\ library. The VM provides an interactive environment for IR manipulation, JIT-compilation, and execution of functions either generated at run-time or loaded from disk: for instance, it allows the user to insert OSR points in loaded functions, run optimization passes on them, display their CFGs, and repeatedly invoke a function for a specified amount of times. \tinyvm\ supports dynamic library loading and linking, and includes a helper component for MCJIT that simplifies tasks such as handling multiple IR modules, symbol resolution in presence of multiple versions of a function, and tracking
native code and other machine-level generated
objects such as Stackmaps. code and data objects.
\tinyvm\ is located in {\small\tt /home/osrkit/Desktop/tinyvm/} and runs a case-insensitite command-line interpreter:
\begin{small}
...
\end{verbatim}
\end{small}
\noindent Use
``help'' {\tt HELP} to print basic documentation on how to use the shell. Usage scenarios are discussed in \ref{ss:art-eval-res}.
\subsubsection{Check-list (artifact meta information)}
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\subsubsection{Session 1: OSR instrumentation in \osrkit}
\tinyvm\ implements a code generator for open OSR points that can dynamically inline
a method whose address function calls to targets that cannot be
determined when the calling function is compiled. statically determined. In the example from \myfigure\ref{fi:isord-example}, a comparator function {\tt c} is passed as argument to function {\tt isord}, which checks whether an array {\tt v}
of numbers is ordered according to the criterion encoded in {\tt c}.
To interactively reproduce the experiment presented in \mysection\ref{se:osr-llvm}, we provide under the folder {\small\tt tinyvm/isord} a C
driver module {\small\tt inline.c} with an LLVM IR counterpart {\small\tt inline.ll} (generated with {\small\tt clang -S -emit-llvm -O1 inline.c}).
\vspace{0.2em}
We can load the IR module in \tinyvm\ and show the code generated for method {\tt isord} with:
\begin{small}
\begin{verbatim}
...
\end{verbatim}
\end{small}
\noindent A $\phi$-node {\tt \%i.01} is used to represent the index of the
C {\tt for}
loop, loop from the C code, and is set to {\tt \%10} when reached from the loop header (basic block {\tt \%2}) {\em after} a loop iteration. In fact, as a result of {\small \tt -O1} optimizations,
with when {\tt n>1} execution jumps from the function entrypoint {\tt \%0} directly into the loop body, initializing the $\phi$-node with {\tt 1}. Comparator {\tt c} is invoked with a tail call, storing its return value into virtual register {\tt \%8}.
OSR points can be inserted with the {\tt INSERT\_OSR} command, which allows several combinations of features (see {\tt HELP} for
details). an exhaustive list). In this session we will modify {\tt isord} so that when the loop body is entered for the first time, an OSR is
promptly aggressively fired:
\begin{small}
\begin{verbatim}
...
\end{verbatim}
\end{small}
\noindent \tinyvm\ will {\tt UPDATE} the function in the following way: an {\tt ALWAYS}-true OSR condition is
verified checked before executing instruction {\tt
\%4}, firing \%4} to fire an {\tt OPEN} OSR transition to the {\tt DYN\_INLINE} code
generator that generator, which will inline any indirect function call to the function pointer {\tt \%c}. We choose {\tt \%4} as location for the OSR as it is the first non-$\phi$ instruction in the loop
body, and body; we
also hint the LLVM back-end through
IR profiling metadata that
the OSR firing
an OSR is {\tt 100}\%-likely.
The IR will now look like:
...
\end{verbatim}
\end{small}
\noindent\osrkit\ has split the {\tt \%.lr.ph}
basic block
at for the OSR
point, condition, also adding an {\tt OSR\_fire} block to transfer the execution state to {\tt isord\_stub} and eventually return the {\tt OSRRet} value.
We can now let {\tt isord} run on
a an array dynamically initialized
array through from the {\tt driver} method, which takes as argument the array length to use. The method will
also populate
it with elements ordered for the comparator in use (see {\small\tt inline.c}). For instance, we
will can ask {\tt driver} to set up an array of $100000$ elements and run {\tt isord} on it:
\begin{small}
\begin{verbatim}
