Camil Demetrescu  over 8 years ago

Commit id: 78125376b57d28cad724611017a99c9c2eeb956f

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\paragraph{OSR Instrumentation in IR.}  To defer the compilation of the continuation function until the comparator is known at run time, we used \osrkit\ to instrument {\tt isord} with an open OSR point at the beginning of the loop body, as shown in \myfigure\ref{fig:isordfrom}. Portions added to the original code by OSR istrumentation are highlighted in grey.  %The figure illustrates how the original {\tt isord} code is instrumented by \tinyvm, highlighting in grey the added portions.   A new basic block is placed at the beginning of the loop body, which increments a hotness counter {\tt p.osr} and jumps to an OSR-firing block if the counter reaches the threshold (1000 iterations in this example). The OSR block contains a tail call to the target generation stub, which receives as parameters the four live variables at the OSR point ({\tt v}, {\tt n}, {\tt i}, {\tt c}). Notice that maintaining the SSA form requires adjusting \osrkit\ to adjust  $\phi$-nodes. The stub (see \myfigure[...]) calls a code generator that: 1) builds an optimized version of {\tt isord} by inlining the comparator (which is known when the OSR is fired), and 2) uses it to create the continuation function {\tt isordto} shown in \myfigure\ref{fig:isordascto}. The stub terminates with a tail call to {\tt isordto}. To generate the continuation function from the optimized version created by the inliner, \osrkit\ replaced the function entry point, removed dead code, replaced live variables with the function parameters, and fixed $\phi$-nodes accordingly. Additions resulting from the IR instrumentation are in grey, while removals are struck-through. \ifdefined\noauthorea  \begin{figure}[t]