viz - visualize data flow graph

yosys> help viz

viz [options] [selection]
Create a graphviz DOT file for the selected part of the design, showing the
relationships between the selected wires, and compile it to a graphics
file (usually SVG or PostScript).
-viewer <viewer>
Run the specified command with the graphics file as parameter.
On Windows, this pauses yosys until the viewer exits.
-format <format>
Generate a graphics file in the specified format. Use 'dot' to just
generate a .dot file, or other <format> strings such as 'svg' or 'ps'
to generate files in other formats (this calls the 'dot' command).
-prefix <prefix>
generate <prefix>.* instead of ~/.yosys_viz.*
wait for the user to press enter to before returning
don't run viewer in the background, IE wait for the viewer tool to
exit before returning
set their group index as 'vg' attribute on cells and wires
-g <selection>
manually define a group of terminal signals. this group is not being
merged with other terminal groups.
-u <selection>
manually define a unique group for each wire in the selection.
-x <selection>
manually exclude wires from being considered. (usually this is
used for global signals, such as reset.)
-s <selection>
like -g, but mark group as 'special', changing the algorithm to
preserve as much info about this groups connectivity as possible.
-G <selection_expr> .
-U <selection_expr> .
-X <selection_expr> .
-S <selection_expr> .
like -u, -g, -x, and -s, but parse all arguments up to a terminating .
as a single select expression. (see 'help select' for details)
-0, -1, -2, -3, -4, -5, -6, -7, -8, -9
select effort level. each level corresponds to an incresingly more
aggressive sequence of strategies for merging nodes of the data flow
graph. (default: 9)
When no <format> is specified, 'dot' is used. When no <format> and <viewer> is
specified, 'xdot' is used to display the schematic (POSIX systems only).

The generated output files are '~/' and '~/.yosys_viz.<format>',
unless another prefix is specified using -prefix <prefix>.

Yosys on Windows and YosysJS use different defaults: The output is written
to '' in the current directory and new viewer is launched each time
the 'show' command is executed.