slides.tex

\documentclass{beamer}
\begin{document}
\title{Compiler Development in Industry}
\author{Aditya Kumar and Sebastian Pop}
\institute{SARC: Samsung Austin R\&D Center}
\date{March 31, 2015}
%\date{\today}

\frame{\titlepage}

\frame{\frametitle{Why is working on compilers interesting?}
  \begin{itemize}
  \item making program execution faster
  \item shrinking executable size
  \item detecting security issues
  \item program analysis and transformation
  \item obfuscation
  \end{itemize}
}

\frame{\frametitle{What sorts of things does a compiler engineer do?}
  day-to-day, working on:
  \begin{itemize}
  \item optimizations
  \item implementing language extensions
  \item improving the breadth of support for hardware features
  \item working with several teams, with open source community
  \item retargetting a compiler to new processors
  \item FP/int arithmetics, static analysis, machine learning \ldots{}
  \item state-of-the-art systems and technologies
  \item fixing bugs and keeping systems running
  \item reading and writing research papers
  \end{itemize}
}

\frame{\frametitle{What drives compiler development?}
  \begin{itemize}
  \item microprocessor and architecture changes
    \begin{itemize}
    \item changes to the ISA: add new instructions, intrinsics
    \item memory and pipeline model: latency of instructions
    \end{itemize}
  \item benchmarks (SPEC, EEMBC, PARSEC, \ldots{})
    \begin{itemize}
    \item avoid regressions: correctness, performance
    \item code is fixed, compiler changes
    \item performance analysis: compare perf of different compilers
    \item profiling critical path, analyzing assembly, perf counters
    \end{itemize}
  \item systems (LAMP stack, Android, Hadoop, \ldots{})
    \begin{itemize}
    \item program and compiler can change
    \item why fixing the compiler when source code can be improved?
    \end{itemize}
  \end{itemize}
}

\frame{\frametitle{Performance analysis and bug reports}
  on the hot path:
  \begin{itemize}
  \item how to increase IPC, ILP, use of SIMD, multi-threading, \ldots{}
  \item how to reduce memory transactions, latency, \ldots{}
  \item why existing optimizations do not apply?
  \item print the IR and decisions of each pass
  \item testcase reduction: delta, c-reduce, bugpoint (LLVM)
  \item analyze the deficiencies in the optimization
  \item share testcase with the community to gather ideas on fix
  \item implement the best idea
  \end{itemize}
}

\frame{\frametitle{Continuous testing}
  100+ commits per day
  \begin{itemize}
  \item compiler changes impact the shape of IR
  \item pattern matching optimizations may not trigger
  \end{itemize}

  \vspace{.5cm}

  How do we keep track of the impact of all these changes?
  \begin{itemize}
  \item nightly testsuite runs
  \item only variable: revisions of the compiler
  \item identify perf, size, compile time, and correctness regressions
  \item statistical methods: noise, smoothing, derivatives, etc.
  \item {\tt git bisect} is awesome
  \item report bug to community
  \end{itemize}
}

\frame{\frametitle{Open source compiler releases}
  \begin{itemize}
  \item GCC
    \begin{itemize}
    \item released once a year, quality based release
    \item dev stages: new development, bug fixing, regression only
    \item release branches only accept regression fixes backports
    \item released compilers are supported for several years
    \end{itemize}
  \item LLVM
    \begin{itemize}
    \item released twice a year, deadline based release
    \item always in new development mode
    \item once released, few or no patches backported
    \item no community support for released compilers
    \end{itemize}
  \end{itemize}
}

\frame{\frametitle{Compiler engineering perspectives}
  \begin{itemize}
  \item many companies have compiler teams
  \item number of compiler engineering positions is increasing
  \item ARM ecosystem adds more processor variations and new architectures to the market
  \item compiler teams are as important as architecture teams to the success of new processors
  \end{itemize}
}

\end{document}