Add image of the compiler pipeline and fix some spelling errors

[matthijs/master-project/dsd-paper.git] / cλash.lhs

diff --git a/cλash.lhs b/cλash.lhs
index 7673139de694e58f66ac4a3218053e62d4755931..b43aca82384bfb88c678106dc94b2f1ca7ee3bef 100644 (file)
--- a/cλash.lhs
+++ b/cλash.lhs
@@ -606,10 +606,7 @@ by an (optimizing) \VHDL\ synthesis tool.
     % against the constructors in the \hs{case} expressions. 
     We can see two versions of a contrived example below, the first 
     using a \hs{case} construct and the other using a \hs{if-then-else} 
     % against the constructors in the \hs{case} expressions. 
     We can see two versions of a contrived example below, the first 
     using a \hs{case} construct and the other using a \hs{if-then-else} 

-    constructs, in the code below. The example sums two values when they are 
-    equal or non-equal (depending on the predicate given) and returns 0 
-    otherwise. Both versions of the example roughly correspond to the same 
-    netlist, which is depicted in \Cref{img:choice}.
+    constructs, in the code below. 

     
     \begin{code}
     sumif pred a b = case pred of
     
     \begin{code}
     sumif pred a b = case pred of


@@ -634,6 +631,11 @@ by an (optimizing) \VHDL\ synthesis tool.
     \caption{Choice - sumif}
     \label{img:choice}
     \end{figure}
     \caption{Choice - sumif}
     \label{img:choice}
     \end{figure}

+    
+    The example sums two values when they are equal or non-equal (depending on 
+    the predicate given) and returns 0 otherwise. Both versions of the example 
+    roughly correspond to the same netlist, which is depicted in 
+    \Cref{img:choice}.

 
     A slightly more complex (but very powerful) form of choice is pattern 
     matching. A function can be defined in multiple clauses, where each clause 
 
     A slightly more complex (but very powerful) form of choice is pattern 
     matching. A function can be defined in multiple clauses, where each clause 


@@ -808,8 +810,8 @@ by an (optimizing) \VHDL\ synthesis tool.
         % value.
       \item[\bf{Multiple constructors with fields}]
         Algebraic datatypes with multiple constructors, where at least
         % value.
       \item[\bf{Multiple constructors with fields}]
         Algebraic datatypes with multiple constructors, where at least

-        one of these constructors has one or more fields are not
-        currently supported.
+        one of these constructors has one or more fields are currently not 
+        supported.

     \end{xlist}
 
   \subsection{Polymorphism}
     \end{xlist}
 
   \subsection{Polymorphism}


@@ -1011,7 +1013,32 @@ by an (optimizing) \VHDL\ synthesis tool.
     
 \section{\CLaSH\ prototype}
 
     
 \section{\CLaSH\ prototype}
 

-foo\par bar
+The \CLaSH\ language as presented above can be translated to \VHDL\ using
+the prototype \CLaSH\ compiler. This compiler allows experimentation with
+the \CLaSH\ language and allows for running \CLaSH\ designs on actual FPGA
+hardware.
+
+\begin{figure}
+\centerline{\includegraphics{compilerpipeline.svg}}
+\caption{\CLaSH\ compiler pipeline}
+\label{img:compilerpipeline}
+\end{figure}
+
+The prototype heavily uses \GHC, the Glasgow Haskell Compiler. 
+\Cref{img:compilerpipeline} shows the \CLaSH\ compiler pipeline. As you can 
+see, the front-end is completely reused from \GHC, which allows the \CLaSH\ 
+prototype to support most of the Haskell Language. The \GHC\ front-end 
+produces the program in the \emph{Core} format, which is a very small, 
+functional, typed language which is relatively easy to process.
+
+The second step in the compilation process is \emph{normalization}. This
+step runs a number of \emph{meaning preserving} transformations on the
+Core program, to bring it into a \emph{normal form}. This normal form
+has a number of restrictions that make the program similar to hardware.
+In particular, a program in normal form no longer has any polymorphism
+or higher order functions.
+
+The final step is a simple translation to \VHDL.

 
 \section{Use cases}
 As an example of a common hardware design where the use of higher-order
 
 \section{Use cases}
 As an example of a common hardware design where the use of higher-order


@@ -1124,7 +1151,7 @@ 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 
 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 description that contain polymorphism or higher-order functions.
+language. 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 
 
 Lava~\cite{Lava} is a hardware description language that focuses on the 
 structural representation of hardware. Besides support for simulation and 


@@ -1133,7 +1160,7 @@ tools for formal verification. Lava descriptions are actually circuit
 generators when viewed from a synthesis viewpoint, in that the language 
 elements of Haskell, such as choice, can be used to guide the circuit 
 generation. If a developer wants to insert a choice element inside an actual 
 generators when viewed from a synthesis viewpoint, in that the language 
 elements of Haskell, such as choice, can be used to guide the circuit 
 generation. If a developer wants to insert a choice element inside an actual 

-circuit he will have to specify this explicitly as a component. 
+circuit he will have to explicitly instantiate a multiplexer-like component. 

 
 In this respect \CLaSH\ differs from Lava, in that all the choice elements, 
 such as case-statements and pattern matching, are synthesized to choice 
 
 In this respect \CLaSH\ differs from Lava, in that all the choice elements, 
 such as case-statements and pattern matching, are synthesized to choice 


@@ -1143,11 +1170,9 @@ mentioned in this section.
 
 The merits of polymorphic typing, combined with higher-order functions, are 
 now also recognized in the `main-stream' hardware description languages, 
 
 The merits of polymorphic typing, combined with higher-order functions, are 
 now also recognized in the `main-stream' hardware description languages, 

-exemplified by the new \VHDL-2008 standard~\cite{VHDL2008}. \VHDL-2008 has 
-support to specify types as generics, thus allowing a developer to describe 
+exemplified by the new \VHDL-2008 standard~\cite{VHDL2008}. \VHDL-2008 support for generics has been extended to types, allowing a developer to describe 

 polymorphic components. Note that those types still require an explicit 
 polymorphic components. Note that those types still require an explicit 

-generic map, whereas type-inference and type-specialization are implicit in 
-\CLaSH.
+generic map, whereas types can be automatically inferred in \CLaSH.

 
 % Wired~\cite{Wired},, T-Ruby~\cite{T-Ruby}, Hydra~\cite{Hydra}. 
 % 
 
 % Wired~\cite{Wired},, T-Ruby~\cite{T-Ruby}, Hydra~\cite{Hydra}. 
 %