Few corrections
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@ -10,6 +10,7 @@
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\usepackage{amssymb}
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\usepackage{booktabs}
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\usepackage{makecell}
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\usepackage{ifthen}
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\usepackage{../shared/my_listings}
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%\usepackage{../shared/my_hyperref}
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@ -23,12 +24,22 @@
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\setbeamertemplate{navigation symbols}{}
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\newcommand{\thenalert}[1]{\only<1>{#1}\only<2>{\alert{#1}}}
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\newcommand{\slidecountline}{
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\ifthenelse{\theframenumber = 0}
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{}
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{\insertframenumber/\inserttotalframenumber}}
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\lstdefinelanguage{gdb}{
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morekeywords={gdb},
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sensitive=false,
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}
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%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
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\author[Théophile Bastian]{Théophile \textsc{Bastian} \\
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\author[\slidecountline]{Théophile \textsc{Bastian} \\
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\small{Under supervision of Francesco Zappa Nardelli}}
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\title{Internship defense, MPRI, M2}
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\subtitle{Speeding up stack unwinding by compiling DWARF debugging data}
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\title[DWARF unwinding data compilation]
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{Speeding up stack unwinding by compiling DWARF debugging data}
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\date{March\ --\ August 2018}
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%\subject{}
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%\logo{}
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@ -40,6 +51,7 @@
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\addtocounter{framenumber}{-1}
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\titlepage{}
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\vspace{-1em}
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\begin{center}
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Slides: \url{https://tobast.fr/m2/slides.pdf} \\
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Report: \url{https://tobast.fr/m2/report.pdf}
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@ -58,21 +70,18 @@
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\subsection{Introduction}
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\begin{frame}[fragile]{We often use stack unwinding!}
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\begin{lstlisting}[language=, numbers=none, escapechar=|]
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\begin{lstlisting}[language=gdb, numbers=none, escapechar=|]
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Program received signal SIGSEGV, Segmentation fault.
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0x0000555555554625 in fct_b (m=0x5c) at segfault.c:5
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5 printf("%l\n", *m);
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|\pause|
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(gdb) backtrace
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|\pause| (gdb) backtrace
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#0 0x0000555555554625 in fct_b (m=0x5c) at segfault.c:5
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#1 0x0000555555554663 in fct_a (n=42) at segfault.c:10
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#2 0x0000555555554674 in main () at segfault.c:14
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|\pause|
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(gdb) frame 1
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|\pause| (gdb) frame 1
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#1 0x0000555555554663 in fct_a (n=42) at segfault.c:10
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10 fct_b((int*)(some_fct_a_var + 8));
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|\pause|
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(gdb) print some_fct_a_var
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|\pause| (gdb) print some_fct_a_var
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$1 = 84
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\end{lstlisting}
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@ -139,8 +148,7 @@ $1 = 84
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%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
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\subsection{DWARF tables}
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\begin{frame}[fragile]{DWARF unwinding data}
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\begin{frame}[fragile, shrink]{DWARF unwinding data}
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\begin{lstlisting}[numbers=none, language=]
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00009b30 48 009b34 FDE cie=0000 pc=0084950..0084b37
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LOC CFA rbx rbp r12 r13 r14 r15 ra
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@ -211,7 +219,7 @@ $1 = 84
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\vspace{2em}
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\begin{center}
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\textbf{Debug data is not only for debugging}
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\textbf{\Large{}Debug data is not only for debugging}
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\end{center}
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\end{frame}
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@ -221,18 +229,6 @@ $1 = 84
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%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
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\subsection{Compilation Strategy}
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\begin{frame}[fragile]{Types}
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Generated data:
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\lstinputlisting[language=C]{src/unwind_context.c}
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\pause{}
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\vspace{1em}
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Function type:
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\begin{lstlisting}[language=C]
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unwind_context_t _eh_elf(
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unwind_context_t, instruction_pointer_t); \end{lstlisting}
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\end{frame}
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\begin{frame}{Compilation overview}
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\begin{itemize}
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\item Compiled to \alert{C code}
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@ -265,39 +261,19 @@ unwind_context_t _eh_elf(
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\item Only supports few common expressions: already $~ 90\,\%$
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of expressions used
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\end{itemize}
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\item Among \alert{4000} randomly sampled filed, only \alert{24}
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containing unsupported instructions
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\end{itemize}
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\end{frame}
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\begin{frame}[fragile]{A word on memory maps}
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\textbf{Various functions come from various ELFs}\\
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\pause{}
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\hfill{}\textbf{\ldots{}and thus various \ehelfs{}}
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\begin{lstlisting}[language=, numbers=none]
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55c81b11e000-55c81b126000 000k /usr/bin/cat
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55c81b325000-55c81b326000 007k /usr/bin/cat
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55c81b326000-55c81b327000 008k /usr/bin/cat
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55c81bcf3000-55c81bd14000 000k [heap]
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7f8a5b4ed000-7f8a5b50f000 000k /usr/lib/libc-2.28.so
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7f8a5b50f000-7f8a5b65a000 022k /usr/lib/libc-2.28.so
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7f8a5b65a000-7f8a5b6a6000 16dk /usr/lib/libc-2.28.so
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7f8a5b6ec000-7f8a5b6ee000 000k /usr/lib/ld-2.28.so
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7f8a5b6ee000-7f8a5b70d000 002k /usr/lib/ld-2.28.so
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7f8a5b70d000-7f8a5b715000 021k /usr/lib/ld-2.28.so
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7ffc8a66b000-7ffc8a68c000 000k [stack]
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7ffc8a74a000-7ffc8a74d000 000k [vvar]
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7ffc8a74d000-7ffc8a74f000 000k [vdso]
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\end{lstlisting}
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\end{frame}
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%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
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\subsection{Outlining}
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\begin{frame}{Size optimisation: outlining}
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\begin{itemize}
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\item This \alert{works}, but \alert{takes space}: about \alert{7 times
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heavier} than regular DWARF\@.
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larger in size} than regular DWARF\@.
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\item DWARF optimisation strategy: \alert{alter previous row}. \\
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Causes slowness: we cannot do that.
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@ -341,7 +317,8 @@ unwind_context_t _eh_elf(
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\pause{}\vspace{1em}
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\begin{itemize}
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\item 2 $\implies$ exit hand-crafted program, exit CSmith
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\item 2 $\implies$ exit hand-crafted program. CSmith did not work
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either.
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\item 5 $\implies$ cannot call the unwinding procedure by hand
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\end{itemize}
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\end{frame}
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@ -387,6 +364,7 @@ unwind_context_t _eh_elf(
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\end{itemize}
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\end{frame}
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\subsection{Libunwind}
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\begin{frame}{libunwind implementation}
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\begin{itemize}
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\item \alert{libunwind}: \textit{de facto} standard library for
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@ -441,87 +419,27 @@ unwind_context_t _eh_elf(
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\begin{tabular}{r r r r r r}
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\toprule
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\thead{Object}
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& \thead{Original \\ program size \\ (KiB)}
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& \thead{Original \\ \lstc{.eh\_frame} \\ (KiB)}
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& \thead{Generated \\ \ehelf{} \\ (KiB)}
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& \thead{\% \\ original \\ size}
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& \thead{Growth \\ factor} \\
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& \thead{\% of binary size}
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& \thead{Growth factor} \\
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\midrule
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libc
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& 1\,434 & 130.1 & 313.2 & 21.88 & 2.41 \\
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& 21.88 & 2.41 \\
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libpthread
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& 58.1 & 11.6 & 25.4 & 43.71 & 2.19 \\
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& 43.71 & 2.19 \\
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ld
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& 129.6 & 9.6 & 28.6 & 22.09 & 2.97 \\
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& 22.09 & 2.97 \\
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hackbench
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& 2.9 & 0.555 & 2.8 & 93.87 & 4.99 \\
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& 93.87 & 4.99 \\
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Total
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& 1\,638 & 151.8 & 370.0 & 22.81 & \alert{2.44} \\
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& 22.81 & \alert{2.44} \\
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\bottomrule
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\end{tabular}
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\end{center}
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\end{frame}
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\newcommand{\ofsupp}[1]{$\left[\text{#1}\right]$}
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\begin{frame}{Instructions coverage}
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\scriptsize\centering
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\begin{tabular}{r r r r r r}
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\toprule
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\thead{}
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& \thead{Undef}
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& \thead{Same \\ value}
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& \thead{Offset}
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& \thead{Val \\ offset}
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& \thead{Reg}
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\\
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\midrule
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\makecell{Only supp. \\ columns} \vspace{.4em}
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& 1698 (0.006\,\%)
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& 0
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& 30\,M (99.9\,\%)
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& 0
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& 14 (0\,\%)
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\\
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All columns
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& 1698 (0.003\,\%)
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& 0
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& 55\,M (99.9\,\%)
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& 0
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& 22 (0\,\%)
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\\
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\bottomrule
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\toprule
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\thead{}
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& \thead{Expr \\ \ofsupp{supported}}
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& \thead{Val \\ expr}
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& \thead{Archi.}
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& & \thead{Total}
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\\
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\midrule
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\makecell{Only supp. \\ columns} \vspace{.4em}
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& \makecell{4475 (0.015\,\%) \\ \ofsupp{81.4\,\%}}
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& 0
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& 0
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& & 30044442
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\\
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All columns
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& \makecell{12367 (0.02\,\%) \\ \ofsupp{91.7\,\%}}
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& 0
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& 0
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& & 54680492
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\\
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\bottomrule
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\end{tabular}
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\vspace{2em}\pause{}
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\textbf{Among \alert{4000} randomly sampled filed, only \alert{24}
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containing unsupported instructions}
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\end{frame}
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%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
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\section{A glance at future work}
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\section*{}
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\begin{frame}{What next?}
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\begin{itemize}
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@ -540,8 +458,6 @@ unwind_context_t _eh_elf(
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\end{frame}
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%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
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\section*{}
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\begin{frame}
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\begin{columns}[c]
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\begin{column}{0.35\textwidth}
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