mirror of https://github.com/YosysHQ/yosys.git
303 lines
9.4 KiB
TeX
303 lines
9.4 KiB
TeX
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\section{Yosys by example -- Advanced Synthesis}
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\begin{frame}
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\sectionpage
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\end{frame}
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\begin{frame}{Overview}
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This section contains 4 subsections:
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\begin{itemize}
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\item Using selections
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\item Advanced uses of techmap
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\item Coarse-grain synthesis
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\item Automatic design changes
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\end{itemize}
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\end{frame}
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%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
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\subsection{Using selections}
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\begin{frame}
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\subsectionpage
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\subsectionpagesuffix
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\end{frame}
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\subsubsection{Simple selections}
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\begin{frame}[fragile]{\subsubsecname}
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Most Yosys commands make use of the ``selection framework'' of Yosys. It can be used
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to apply commands only to part of the design. For example:
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\medskip
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\begin{lstlisting}[xleftmargin=0.5cm, basicstyle=\ttfamily\fontsize{8pt}{10pt}\selectfont, language=ys]
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delete # will delete the whole design, but
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delete foobar # will only delete the module foobar.
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\end{lstlisting}
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\bigskip
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The {\tt select} command can be used to create a selection for subsequent
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commands. For example:
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\medskip
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\begin{lstlisting}[xleftmargin=0.5cm, basicstyle=\ttfamily\fontsize{8pt}{10pt}\selectfont, language=ys]
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select foobar # select the module foobar
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delete # delete selected objects
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select -clear # reset selection (select whole design)
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\end{lstlisting}
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\end{frame}
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\subsubsection{Selection by object name}
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\begin{frame}[fragile]{\subsubsecname}
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The easiest way to select objects is by object name. This is usually only done
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in synthesis scripts that are hand-tailored for a specific design.
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\bigskip
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\begin{lstlisting}[xleftmargin=0.5cm, basicstyle=\ttfamily\fontsize{8pt}{10pt}\selectfont, language=ys]
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select foobar # select module foobar
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select foo* # select all modules whose names start with foo
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select foo*/bar* # select all objects matching bar* from modules matching foo*
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select */clk # select objects named clk from all modules
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\end{lstlisting}
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\end{frame}
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\subsubsection{Module and design context}
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\begin{frame}[fragile]{\subsubsecname}
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Commands can be executed in {\it module\/} or {\it design\/} context. Until now all
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commands have been executed in design context. The {\tt cd} command can be used
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to switch to module context.
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\bigskip
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In module context all commands only effect the active module. Objects in the module
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are selected without the {\tt <module\_name>/} prefix. For example:
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\bigskip
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\begin{lstlisting}[xleftmargin=0.5cm, basicstyle=\ttfamily\fontsize{8pt}{10pt}\selectfont, language=ys]
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cd foo # switch to module foo
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delete bar # delete object foo/bar
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cd mycpu # switch to module mycpu
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dump reg_* # print details on all objects whose names start with reg_
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cd .. # switch back to design
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\end{lstlisting}
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\bigskip
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Note: Most synthesis script never switch to module context. But it is a very powerful
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tool for interactive design investigation.
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\end{frame}
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\subsubsection{Selecting by object property or type}
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\begin{frame}[fragile]{\subsubsecname}
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Special pattern can be used to select by object property or type. For example:
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\bigskip
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\begin{lstlisting}[xleftmargin=0.5cm, basicstyle=\ttfamily\fontsize{8pt}{10pt}\selectfont, language=ys]
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select w:reg_* # select all wires whose names start with reg_
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select a:foobar # select all objects with the attribute foobar set
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select a:foobar=42 # select all objects with the attribute foobar set to 42
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select A:blabla # select all module with the attribute blabla set
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select foo/t:$add # select all $add cells from the module foo
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\end{lstlisting}
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\bigskip
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A complete list of this pattern expressions can be found in the command
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reference to the {\tt select} command.
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\end{frame}
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\subsubsection{Combining selection}
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\begin{frame}[fragile]{\subsubsecname}
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When more than one selection expression is used in one statement they are
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pushed on a stack. At the final elements on the stack are combined into a union:
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\medskip
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\begin{lstlisting}[xleftmargin=0.5cm, basicstyle=\ttfamily\fontsize{8pt}{10pt}\selectfont, language=ys]
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select t:$dff r:WIDTH>1 # all cells of type $dff and/or with a parameter WIDTH > 1
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\end{lstlisting}
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\bigskip
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Special \%-commands can be used to combine the elements on the stack:
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\medskip
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\begin{lstlisting}[xleftmargin=0.5cm, basicstyle=\ttfamily\fontsize{8pt}{10pt}\selectfont, language=ys]
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select t:$dff r:WIDTH>1 %i # all cells of type $dff *AND* with a parameter WIDTH > 1
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\end{lstlisting}
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\medskip
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\begin{block}{Examples for {\tt \%}-codes (see {\tt help select} for full list)}
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{\tt \%u} \dotfill union of top two elements on stack -- pop 2, push 1 \\
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{\tt \%d} \dotfill difference of top two elements on stack -- pop 2, push 1 \\
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{\tt \%i} \dotfill intersection of top two elements on stack -- pop 2, push 1 \\
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{\tt \%n} \dotfill inverse of top element on stack -- pop 1, push 1 \\
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\end{block}
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\end{frame}
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\subsubsection{Expanding selections}
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\begin{frame}[fragile]{\subsubsecname}
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Selections of cells and wires can be expanded along connections using {\tt \%}-codes
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for selecting input cones ({\tt \%ci}), output cones ({\tt \%co}), or both ({\tt \%x}).
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\medskip
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\begin{lstlisting}[xleftmargin=0.5cm, basicstyle=\ttfamily\fontsize{8pt}{10pt}\selectfont, language=ys]
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# select all wires that are inputs to $add cells
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select t:$add %ci w:* %i
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\end{lstlisting}
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\bigskip
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Additional constraints such as port names can be specified.
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\medskip
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\begin{lstlisting}[xleftmargin=0.5cm, basicstyle=\ttfamily\fontsize{8pt}{10pt}\selectfont, language=ys]
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# select all wires that connect a "Q" output with a "D" input
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select c:* %co:+[Q] w:* %i c:* %ci:+[D] w:* %i %i
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# select the multiplexer tree that drives the signal 'state'
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select state %ci*:+$mux,$pmux[A,B,Y]
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\end{lstlisting}
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\bigskip
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See {\tt help select} for full documentation of this expressions.
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\end{frame}
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\subsubsection{Incremental selection}
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\begin{frame}[fragile]{\subsubsecname}
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Sometime a selection can most easily described by a series of add/delete operations.
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For the commands {\tt select -add} and {\tt select -del} add or remove objects
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from the current selection instead of overwriting it.
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\medskip
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\begin{lstlisting}[xleftmargin=0.5cm, basicstyle=\ttfamily\fontsize{8pt}{10pt}\selectfont, language=ys]
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select -none # start with an empty selection
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select -add reg_* # select a bunch of objects
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select -del reg_42 # but not this one
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select -add state %ci # and add mor stuff
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\end{lstlisting}
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\bigskip
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Within a select expression the token {\tt \%} can be used to push the previous selection
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on the stack.
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\medskip
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\begin{lstlisting}[xleftmargin=0.5cm, basicstyle=\ttfamily\fontsize{8pt}{10pt}\selectfont, language=ys]
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select t:$add t:$sub # select all $add and $sub cells
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select % %ci % %d # select only the input wires to those cells
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\end{lstlisting}
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\end{frame}
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\subsubsection{Creating selection variables}
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\begin{frame}[fragile]{\subsubsecname}
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Selections can be stored under a name with the {\tt select -set <name>}
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command. The stored selections can be used in later select expressions
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using the syntax {\tt @<name>}.
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\medskip
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\begin{lstlisting}[xleftmargin=0.5cm, basicstyle=\ttfamily\fontsize{8pt}{10pt}\selectfont, language=ys]
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select -set cone_a state_a %ci*:-$dff # set @cone_a to the input cone of state_a
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select -set cone_b state_b %ci*:-$dff # set @cone_b to the input cone of state_b
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select @cone_a @cone_b %i # select the objects that are in both cones
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\end{lstlisting}
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\bigskip
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Remember that select expressions can also be used directly as arguments to most
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commands. Some commands also except a single select argument to some options.
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In those cases selection variables must be used to capture more complex selections.
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\medskip
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\begin{lstlisting}[xleftmargin=0.5cm, basicstyle=\ttfamily\fontsize{8pt}{10pt}\selectfont, language=ys]
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dump @cone_a @cone_b
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select -set cone_ab @cone_a @cone_b %i
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show -color red @cone_ab -color magenta @cone_a -color blue @cone_b
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\end{lstlisting}
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\end{frame}
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\begin{frame}[fragile]{\subsubsecname{} -- Example}
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\begin{columns}
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\column[t]{4cm}
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\lstinputlisting[basicstyle=\ttfamily\fontsize{6pt}{7pt}\selectfont, language=verilog]{PRESENTATION_ExAdv/select_01.v}
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\column[t]{7cm}
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\lstinputlisting[basicstyle=\ttfamily\fontsize{8pt}{10pt}\selectfont, language=ys, frame=single]{PRESENTATION_ExAdv/select_01.ys}
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\end{columns}
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\hfil\includegraphics[width=\linewidth,trim=0 0cm 0 0cm]{PRESENTATION_ExAdv/select_01.pdf}
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\end{frame}
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%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
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\subsection{Advanced uses of techmap}
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\begin{frame}
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\subsectionpage
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\subsectionpagesuffix
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\end{frame}
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\subsubsection{TBD}
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\begin{frame}{\subsubsecname}
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TBD
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\end{frame}
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%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
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\subsection{Coarse-grain synthesis}
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\begin{frame}
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\subsectionpage
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\subsectionpagesuffix
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\end{frame}
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\subsubsection{TBD}
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\begin{frame}{\subsubsecname}
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TBD
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\end{frame}
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%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
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\subsection{Automatic design changes}
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\begin{frame}
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\subsectionpage
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\subsectionpagesuffix
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\end{frame}
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\subsubsection{TBD}
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\begin{frame}{\subsubsecname}
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TBD
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\end{frame}
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%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
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\subsection{Summary}
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\begin{frame}{\subsecname}
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\begin{itemize}
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\item TBD
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\item TBD
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\item TBD
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\item TBD
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\end{itemize}
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\bigskip
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\bigskip
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\begin{center}
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Questions?
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\end{center}
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\bigskip
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\bigskip
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\begin{center}
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\url{http://www.clifford.at/yosys/}
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\end{center}
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\end{frame}
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