Merge branch 'master' of http://git.stderr.nl/matthijs/master-project/paper

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

diff --git a/cλash.lhs b/cλash.lhs
index 7673139de694e58f66ac4a3218053e62d4755931..6f158b5edc0b4e04357e51977bfb7a6ca8ab9e3f 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 


@@ -1011,7 +1013,27 @@ 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.
+
+\comment{Add clash pipeline image}
+The prototype heavily uses \GHC, the Glasgow Haskell Compiler. Figure
+TODO shows the \CLaSH compiler pipeline. As you can see, the frontend
+is completely reused from \GHC, which allows the \CLaSH prototype to
+support most of the Haskell Language. The \GHC frontend 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


@@ -1133,7 +1155,7 @@ 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 +1165,9 @@ 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}. 
 %