Daniele Cono D'Elia edited case-study.tex  over 8 years ago

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When the IIR compiler processes an annotated {\tt feval} instruction, it will store in the metadata of the function version being compiled a copy of its variable map (i.e., a map between IIR and IR objects), the current {\tt llvm::BasicBlock*} created for the call and the {\tt llvm::Value*} object corresponding to the first argument for the {\tt feval}. The last two objects are used by the helper component as source label and profiling value for inserting an open OSR point, with the copy of the variable map being passed (along with other information) as {\tt extra} field. The open-OSR stub will in turn invoke the callback optimizer component we are about to describe in the next subsection.  \subsection{Generating optimized code}  The core of the optimization pipeline is the callback optimizer component, that is responsible for generating optimized code for the current function $f$ using profiling (i.e., the object containing the first argument for \feval\) and contextual information passed from the open-OSR stub. As a first step, the optimizer will process the profiling object to resolve the target of the call, which we call $g$. Then, a new function $f_OSR$ $f_{OSR}$  is generated by cloning the IIR representation $R$ of $f$ into $R_{OSR}$  and replacing all the \feval\ instructions calls  in the same group of the instrumented one with direct calls to $g$.