\pgfuseimage{Workflow}
\end{frame}
-\section{Tasks}
-
- \subsection{Original tasks}
- \begin{frame}{Original tasks}
- \begin{itemize}
- \item Select LLVM transformations
- \item Improve and add transformations
- \item Provide debugging information
- \end{itemize}
- \end{frame}
-
- \subsection{Extra tasks}
- \begin{frame}{Extra tasks}
- \begin{itemize}
- \item What is MontiumC?
- \item What is Montium IR?
- \item Reconfigurable binaries
- \end{itemize}
- \end{frame}
-
+\section{Past work}
\begin{frame}{What is MontiumC?}
\note{Two angles: What do we want, and what do we support.}
\begin{itemize}
\item Challenges:
\begin{itemize}
\item Clang is nontransparent
- \note[item]{Clang --- A lot of special cases}
+ \note[item]{Clang --- A lot of special cases. Clang goal: Produce
+ valid LLVM IR, which can change unexpectedly}
\item C is complex
\note[item]{Complex C --- A lot of corner cases}
\item C is limited
void run(void) {
for (int i=0; i<10; ++i)
- output[i] = input[i] * 2;
+ output[i] = mul(input[i], 2);
}
\end{Verbatim}
\end{column}
\end{frame}
\note{} % Empty filler note page
- \begin{frame}{What is Montium IR?}
+ \begin{frame}{Using LLVM transformations}
\begin{itemize}
- \item Status: Initial version
\item Challenges:
\begin{itemize}
- \item Backend is a fast moving target
- \item Corner cases
- \note[item]{Corner case --- global constants}
- \item Hardware dependencies
- \note[item]{Hardware --- Limited number of conditionals possible}
+ \item LLVM Passes assume a lot
+ \note[item]{Assumptions --- Immediates are free, reordering of
+ instructions is possible, shifts are cheaper than mults}
+ \item Montium has specific constraints
+ \note[item]{Constraint --- Implicit cycle boundaries and ordering}
+ \item Montium needs different policies
+ \note[item]{Policies --- Montium has different optimality criteria (or
+ sometimes feasibility criteria) than regular hardware.}
\end{itemize}
\end{itemize}
\end{frame}
- \begin{frame}{Selecting LLVM transformations}
+ \begin{frame}{Using LLVM transformations}
\begin{itemize}
- \item Status: Done
- \item Challenges:
+ \item Achievements:
\begin{itemize}
- \item LLVM Passes assume a lot
- \note[item]{Assumptions --- Immediates are not free}
- \item Montium has specific constraints
- \note[item]{Constraint --- Implicit cycle boundaries and ordering}
+ \item Allow nested functions
+ \begin{itemize}
+ \item Inlining
+ \end{itemize}
+ \item Allow local variables
+ \begin{itemize}
+ \item Stack slots turned into (virtual) registers.
+ \end{itemize}
+ \item Allow use of structs
+ \begin{itemize}
+ \item Promotion to multiple scalar values
+ \end{itemize}
+ \item Allow more different loops
+ \begin{itemize}
+ \item Canonicalization of loops
+ \item Still requires backend support
+ \end{itemize}
+ \item Allow constant function parameters
+ \begin{itemize}
+ \item Constant propagation
+ \end{itemize}
\end{itemize}
\end{itemize}
+ \note[item]{Without transformations, MontiumC hardly exists.
+ Transformations have the goal of making MontiumC bigger.}
\end{frame}
- \begin{frame}{Improving / adding transformations}
+ \begin{frame}{Creating new transformations}
\begin{itemize}
- \item Status: Ongoing
+ \item Existing LLVM transformations are not sufficient for our demands
\item Challenges:
\begin{itemize}
\item Staying generic
- \note[item]{Generic --- LLVM maintained passes are a lot easier}
- \item New LLVM features
+ \note[item]{Generic --- LLVM maintained passes are a lot less work on
+ the long term, but require more initial effort}
+ \item New LLVM features needed
\note[item]{Features --- Multiple return values, inlining and
annotation attributes}
\end{itemize}
\end{itemize}
\end{frame}
- \begin{frame}{Debugging information}
+ \begin{frame}{Creating new transformations}
\begin{itemize}
- \item Status: Not started
- \item Challenges:
+ \item Achievements:
\begin{itemize}
- \item Not much LLVM support yet
- \note[item]{LLVM support --- New in clang/backend, no support in
- transformations yet.}
- \item Transformations
- \note[item]{Transformations --- Global arguments, argument addition,
- removal, etc.}
+ \item Allow global variables
+ \begin{itemize}
+ \item Turned into local variables
+ \end{itemize}
+ \item Simpler backend
+ \begin{itemize}
+ \item Perform canonicalizations
+ \note[item]{Canonical --- Maximal SSA form, removal of global variables}
+ \end{itemize}
+ \item Reconfigurability
+ \begin{itemize}
+ \item Preserving reconfigurable variables
+ \item Mainly needs backend support
+ \end{itemize}
+ \item Allow different constant function parameters
+ \begin{itemize}
+ \item Function duplication
+ \item Not in use yet
+ \note[item]{Function duplication challenge --- When to duplicate?}
+ \end{itemize}
\end{itemize}
\end{itemize}
\end{frame}
- \begin{frame}{Reconfigurable binaries}
+ \begin{frame}[containsverbatim]{Constant propagation}
+ \begin{columns}
+ \begin{column}{0.5\textwidth}
+ Before
+ \begin{Verbatim}[fontsize=\tiny]
+
+int mul(int a, int b) {
+ return a * b;
+}
+
+void run(void) {
+ ...
+ mul(x, 2);
+ ...
+ mul(y, 2);
+ ...
+}
+ \end{Verbatim}
+ \end{column}
+ \begin{column}{0.5\textwidth}
+ After
+ \begin{Verbatim}[fontsize=\tiny]
+
+int mul(int a) {
+ return a * 2;
+}
+
+void run(void) {
+ ...
+ mul(x);
+ ...
+ mul(y);
+ ...
+}
+ \end{Verbatim}
+ \end{column}
+ \end{columns}
+ \note{Mainly useful when using library code}
+ \end{frame}
+
+ \begin{frame}[containsverbatim]{Function duplication}
+ \begin{columns}
+ \begin{column}{0.5\textwidth}
+ Before
+ \begin{Verbatim}[fontsize=\tiny]
+
+int mul(int a, int b) {
+ return a * b;
+}
+
+void run(void) {
+ ...
+ mul(x, 2);
+ ...
+ mul(y, 2);
+ ...
+ mul(z, 4);
+ ...
+ mul(w, 4);
+ ...
+}
+ \end{Verbatim}
+ \end{column}
+ \begin{column}{0.5\textwidth}
+ After
+ \begin{Verbatim}[fontsize=\tiny]
+
+int mul2(int a) {
+ return a * 2;
+}
+
+int mul4(int a) {
+ return a * 4;
+}
+
+void run(void) {
+ ...
+ mul2(x);
+ ...
+ mul2(y);
+ ...
+ mul4(z);
+ ...
+ mul4(w);
+ ...
+}
+ \end{Verbatim}
+ \end{column}
+ \end{columns}
+ \note{Mainly useful when values must really be constant (masks, loop
+ counters)}
+ \end{frame}
+
+\section{Future work}
+ \begin{frame}{Open issues}
\begin{itemize}
- \item Status: Recently started
- \item Challenges:
+ \item Debug information
\begin{itemize}
- \item Tracking variables
- \note[item]{Tracking --- Through all steps of the process}
- \item Loss of optimizations
- \note[item]{Optimizations --- Hard to encode constraints}
- \item Mostly a backend problem
+ \item Only time for initial work
+ \end{itemize}
+ \item Reconfigurability
+ \begin{itemize}
+ \item Needs backend support
+ \end{itemize}
+ \item Proper inlining
+ \item Memory access
+ \begin{itemize}
+ \item Needs backend support
+ \end{itemize}
+ \item Remove next\_cycle
+ \begin{itemize}
+ \item Backend only
\end{itemize}
\end{itemize}
\end{frame}
-\section{Work process}
- \begin{frame}{Working at Recore}
- \begin{itemize}
- \item Smart people
- \item Fast communication
- \note[item]{Communication --- Mixed teams, easy to "listen in".}
- \item Constructive brainstorming
- \note[item]{Brainstorming --- Evaluating different ideas and approaches.}
- \end{itemize}
- \end{frame}
-
- \begin{frame}{Working with LLVM}
- \begin{itemize}
- \item Large community
- \note[item]{Community --- Companies involved, a lot of full time
- developers.}
- \item Great support
- \note[item]{Support --- mailing list, bug reports solved within 1/2 days.}
- \item Slightly conflicting goals
- \note[item]{Goals --- LLVM aims mainly at "regular" architectures.}
- \end{itemize}
- \end{frame}
-
\section{Conclusions}
\begin{frame}{Conclusions}
\begin{itemize}
\item LLVM is very suitable
\item Defining the problem is harder than solving it
- \item Three months is short!
+ \item Three months is short, visible progress is slow
\end{itemize}
\end{frame}
projects / matthijs / projects / internship.git / commitdiff