% Macro for certain acronyms in small caps. Doesn't work with the
% default font, though (it contains no smallcaps it seems).
\def\acro#1{{\small{#1}}}
+\def\acrotiny#1{{\scriptsize{#1}}}
\def\VHDL{\acro{VHDL}}
\def\GHC{\acro{GHC}}
\def\CLaSH{{\small{C}}$\lambda$a{\small{SH}}}
+\def\CLaSHtiny{{\scriptsize{C}}$\lambda$a{\scriptsize{SH}}}
% Macro for pretty printing haskell snippets. Just monospaced for now, perhaps
% we'll get something more complex later on.
% author names and affiliations
% use a multiple column layout for up to three different
% affiliations
-\author{\IEEEauthorblockN{Christiaan P.R. Baaij, Matthijs Kooijman, Jan Kuper, Marco E.T. Gerards, Bert Molenkamp, Sabih H. Gerez}
-\IEEEauthorblockA{University of Twente, Department of EEMCS\\
+\author{\IEEEauthorblockN{Christiaan P.R. Baaij, Matthijs Kooijman, Jan Kuper, Marco E.T. Gerards}%, Bert Molenkamp, Sabih H. Gerez}
+\IEEEauthorblockA{%Computer Architecture for Embedded Systems (CAES)\\
+Department of EEMCS, University of Twente\\
P.O. Box 217, 7500 AE, Enschede, The Netherlands\\
c.p.r.baaij@@utwente.nl, matthijs@@stdin.nl, j.kuper@@utwente.nl}}
% \and
\section{Introduction}
-Hardware description languages has allowed the productivity of hardware
+Hardware description languages have allowed the productivity of hardware
engineers to keep pace with the development of chip technology. Standard
Hardware description languages, like \VHDL~\cite{VHDL2008} and
Verilog~\cite{Verilog}, allowed an engineer to describe circuits using a
and types that together form the language primitives of the domain specific
language. As a result of how the signals are modeled and abstracted, the
functions used to describe a circuit also build a large domain-specific
-datatype (hidden from the designer) which can be further processed by an
+datatype (hidden from the designer) which can then be processed further by an
embedded compiler. This compiler actually runs in the same environment as the
description; as a result compile-time and run-time become hard to define, as
the embedded compiler is usually compiled by the same Haskell compiler as the
capture certain language constructs, such as Haskell's choice elements
(if-constructs, case-constructs, pattern matching, etc.), which are not
available in the functional hardware description languages that are embedded
-in Haskell as a domain specific languages. As far as the authors know, such
+in Haskell as a domain specific language. As far as the authors know, such
extensive support for choice-elements is new in the domain of functional
hardware description languages. As the hardware descriptions are plain Haskell
functions, these descriptions can be compiled for simulation using an
Where descriptions in a conventional hardware description language have an
explicit clock for the purpose state and synchronicity, the clock is implied
in this research. A developer describes the behavior of the hardware between
-clock cycles, as such, only synchronous systems can be described. Many
-functional hardware description model signals as a stream of all values over
-time; state is then modeled as a delay on this stream of values. The approach
-taken in this research is to make the current state of a circuit part of the
-input of the function and the updated state part of the output.
+clock cycles. Many functional hardware description model signals as a stream
+of all values over time; state is then modeled as a delay on this stream of
+values. The approach taken in this research is to make the current state of a
+circuit part of the input of the function and the updated state part of the
+output. The current abstraction of state and time limits the descriptions to
+synchronous hardware, there however is room within the language to eventually
+add a different abstraction mechanism that will allow for the modeling of
+asynchronous systems.
Like the standard hardware description languages, descriptions made in a
functional hardware description language must eventually be converted into a
-netlist. This research also features a prototype translator called \CLaSH\
-(pronounced: clash), which converts the Haskell code to equivalently behaving
-synthesizable \VHDL\ code, ready to be converted to an actual netlist format
-by an (optimizing) \VHDL\ synthesis tool.
+netlist. This research also features a prototype translator, which has the
+same name as the language: \CLaSH\footnote{\CLaSHtiny: \acrotiny{CAES}
+Language for Synchronous Hardware} (pronounced: clash). This compiler converts
+the Haskell code to equivalently behaving synthesizable \VHDL\ code, ready to
+be converted to an actual netlist format by an (optimizing) \VHDL\ synthesis
+tool.
+
+Besides trivial circuits such as variants of both the FIR filter and the
+simple CPU shown in \Cref{sec:usecases}, the \CLaSH\ compiler has also been
+shown to work for non-trivial descriptions. \CLaSH\ has been able to
+successfully translate the functional description of a streaming reduction
+circuit~\cite{reductioncircuit} for floating point numbers.
\section{Hardware description in Haskell}
\end{inparaenum}
The output port can have a complex type (such as a tuple), so having just
a single output port does not pose any limitation. The arguments of a
- function applications are assigned to a signal, which are then mapped to
+ function application are assigned to signals, which are then mapped to
the corresponding input ports of the component. The output port of the
function is also mapped to a signal, which is used as the result of the
application itself.
(\Cref{img:choice}) as the earlier two versions of the example.
\begin{code}
- sumif Eq a b | a == b = a + b
- sumif Neq a b | a != b = a + b
- sumif _ _ _ = 0
+ sumif Eq a b | a == b = a + b
+ | otherwise = 0
+ sumif Neq a b | a != b = a + b
+ | otherwise = 0
\end{code}
% \begin{figure}
value in the input list corresponds to exactly one cycle of the (implicit)
clock. The result of the simulation is a list of outputs for every clock
cycle. As both the \hs{run} function and the hardware description are
- plain hardware, the complete simulation can be compiled by an optimizing
+ plain Haskell, the complete simulation can be compiled by an optimizing
Haskell compiler.
\section{\CLaSH\ prototype}
\begin{figure}
\centerline{\includegraphics{compilerpipeline.svg}}
-\caption{\CLaSH\ compiler pipeline}
+\caption{\CLaSHtiny\ compiler pipeline}
\label{img:compilerpipeline}
\end{figure}
The final step is a simple translation to \VHDL.
\section{Use cases}
+\label{sec:usecases}
As an example of a common hardware design where the use of higher-order
functions leads to a very natural description is a FIR filter, which is
basically the dot-product of two vectors:
\begin{figure}
\centerline{\includegraphics{4tapfir.svg}}
-\caption{4-taps FIR Filter}
+\caption{4-taps \acrotiny{FIR} Filter}
\label{img:4tapfir}
\end{figure}
heterogeneous models of computation, which include continuous time,
synchronous and untimed models of computation. Using so-called domain
interfaces a designer can simulate electronic systems which have both analog
-as digital parts. ForSyDe has several simulation and synthesis backends,
-though synthesis is restricted to the synchronous subset of the ForSyDe
-language. Unlike \CLaSH\ there is no support for the automated synthesis of descriptions that contain polymorphism or higher-order functions.
+as digital parts. ForSyDe has several backends including simulation and
+automated synthesis, though automated synthesis is restricted to the
+synchronous model of computation within ForSyDe. Unlike \CLaSH\ there is no
+support for the automated synthesis of descriptions that contain polymorphism
+or higher-order functions.
Lava~\cite{Lava} is a hardware description language that focuses on the
structural representation of hardware. Besides support for simulation and
% http://www.michaelshell.org/tex/ieeetran/bibtex/
\bibliographystyle{IEEEtran}
% argument is your BibTeX string definitions and bibliography database(s)
-\bibliography{IEEEabrv,clash.bib}
+\bibliography{clash}
%
% <OR> manually copy in the resultant .bbl file
% set second argument of \begin to the number of references
projects / matthijs / master-project / dsd-paper.git / blobdiff