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355 lines
12 KiB
ReStructuredText
355 lines
12 KiB
ReStructuredText
Generated help messages and documentation
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=========================================
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All Yosys commands and built-in cell types should include help text, documenting
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their functionality for users. This help text is made available through the
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`help` command, and online via `ReadtheDocs`_ as part of the :doc:`/cmd_ref` and
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:doc:`/cell_index` documentation. When running locally, any commands provided
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by loaded plugins (either from the command line when calling ``yosys``, or
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dynamically with the `plugin` command) will also be available to the `help`
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command.
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.. _ReadtheDocs: https://about.readthedocs.com/
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.. note::
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Since help text for commands is generated from compiled code, the online help
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may differ from that produced by `help`. Some commands, like `abc`, may be
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completely unavailable depending on compile flags; while others may limit
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specific features, such as whether the `synth` script pass uses ABC.
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Command help
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------------
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The first stop for command help text is the ``Pass::short_help``. This is a
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short sentence describing the pass, and is set in the ``Pass`` constructor, as
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demonstrated here with `chformal`.
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.. literalinclude:: /generated/chformal.cc
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:language: c++
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:start-at: public Pass {
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:end-before: bool formatted_help()
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:caption: ``ChformalPass()`` from :file:`passes/cmds/chformal.cc`
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:append: // ...
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} ChformalPass;
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All currently available commands are listed with their ``short_help`` string
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when calling `help` without arguments, and is more or less the same as the
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unlisted :ref:`command index <commandindex>`. The string is also used when
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hovering over links to commands in the documentation, and in section headings
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like :ref:`chformal autocmd`.
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The next section shows the complete help text for the `chformal` command. This
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can be displayed locally by using ``help <command>`` (or ``yosys -h <command>``
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from the command line). The general format is to show each usage signature,
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followed by a paragraph describing what the pass does, and a list of options or
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flags available. Additional arguments in the signature or option may use square
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brackets (``[]``) to indicate optional parts, and angle brackets (``<>``) for
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required parts. The pipe character ``|`` may be used to indicate mutually
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exclusive arguments.
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.. todo:: decide on a formatting style for pass options
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.. _chformal autocmd:
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.. autocmd:: chformal
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:noindex:
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The ``Pass::help()`` method
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~~~~~~~~~~~~~~~~~~~~~~~~~~~
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This is the original way to provide help text, and as of this writing is still
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the most common. The ``log()`` function should be called directly to print and
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format the help text, and each line should be limited to 80 (printed)
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characters. While it is possible to provide arbitrary formatting, it is
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preferred to follow the guidelines here to maintain consistency with other
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passes and to assist in correct parsing and formatting during RST generation
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(i.e. these docs).
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The first line should always be a blank line, followed by the primary usage
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signature for the command. Each usage signature should be indented with 4
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spaces, and followed by a blank line. Each option or flag should start on a new
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line indented with 4 spaces, followed by a description of the option which is
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indented by a further 4 spaces, and then a blank line. Option descriptions
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typically start with lower case, and may forgo a trailing period (``.``). Where
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multiple options share a description the blank line between options should be
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omitted.
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The ``Pass::formatted_help()`` method
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~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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- ``PrettyHelp::get_current()``
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- ``PrettyHelp::set_group()``
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+ used with ``.. autocmdgroup:: <group>``
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+ can assign group and return false
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+ if no group is set, will try to use ``source_location`` and assign group
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from path to source file
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- return value
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+ true means help content added to current ``PrettyHelp``
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+ false to use ``Pass::help()``
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- adding content
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+ help content is a list of ``ContentListing`` nodes, each one having a type,
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body, and its own list of children ``ContentListing``\ s
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+ ``PrettyHelp::get_root()`` returns the root ``ContentListing`` (``type="root"``)
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+ ``ContentListing::{usage, option, codeblock, paragraph}`` each add a
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``ContentListing`` to the current node, with type the same as the method
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* the first argument is the body of the new node
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* ``usage`` shows how to call the command (i.e. its "signature")
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* ``paragraph`` content is formatted as a paragraph of text with line breaks
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added automatically
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* ``codeblock`` content is displayed verbatim, use line breaks as desired;
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takes an optional ``language`` argument for assigning the language in RST
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output for code syntax highlighting (use ``yoscrypt`` for yosys script
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syntax highlighting)
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* ``option`` lists a single option for the command, usually starting with a
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dash (``-``); takes an optional second argument which adds a paragraph
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node as a means of description
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+ ``ContentListing::open_usage`` creates and returns a new usage node, can be
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used to e.g. add text/options specific to a given usage of the command
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+ ``ContentListing::open_option`` creates and returns a new option node, can
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be used to e.g. add multiple paragraphs to an option's description
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+ paragraphs are treated as raw RST, allowing for inline formatting and
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references as if it were written in the RST file itself
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.. literalinclude:: /generated/chformal.cc
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:language: c++
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:start-at: bool formatted_help()
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:end-before: void execute
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:caption: ``ChformalPass::formatted_help()`` from :file:`passes/cmds/chformal.cc`
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Dumping command help to json
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~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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- `help -dump-cmds-json cmds.json`
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+ generates a ``ContentListing`` for each command registered in Yosys
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+ tries to parse unformatted ``Pass::help()`` output if
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``Pass::formatted_help()`` is unimplemented or returns false
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* if a line starts with four spaces followed by the name of the command then
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a space, it is parsed as a signature (usage node)
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* if a line is indented and starts with a dash (``-``), it is parsed as an
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option
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* anything else is parsed as a codeblock and added to either the root node
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or the current option depending on the indentation
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+ dictionary of command name to ``ContentListing``
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* uses ``ContentListing::to_json()`` recursively for each node in root
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* root node used for source location of class definition
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* includes flags set during pass constructor (e.g. ``experimental_flag`` set
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by ``Pass::experimental()``)
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* also title (``short_help`` argument in ``Pass::Pass``), group, and class
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name
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+ dictionary of group name to list of commands in that group
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- used by sphinx autodoc to generate help content
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.. literalinclude:: /generated/cmds.json
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:language: json
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:start-at: "chformal": {
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:end-before: "chparam": {
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:caption: `chformal` in generated :file:`cmds.json`
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.. note:: Synthesis command scripts are special cased
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If the final block of help output starts with the string ``"The following
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commands are executed by this synthesis command:\n"``, then the rest of the
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code block is formatted as ``yoscrypt`` (e.g. `synth_ice40`). The caveat
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here is that if the ``script()`` calls ``run()`` on any commands *prior* to
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the first ``check_label`` then the auto detection will break and revert to
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unformatted code (e.g. `synth_fabulous`).
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Command line rendering
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~~~~~~~~~~~~~~~~~~~~~~
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- if ``Pass::formatted_help()`` returns true, will call
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``PrettyHelp::log_help()``
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+ traverse over the children of the root node and render as plain text
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+ effectively the reverse of converting unformatted ``Pass::help()`` text
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+ lines are broken at 80 characters while maintaining indentation (controlled
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by ``MAX_LINE_LEN`` in :file:`kernel/log_help.cc`)
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+ each line is broken into words separated by spaces, if a given word starts
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and ends with backticks they will be stripped
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- if it returns false it will call ``Pass::help()`` which should call ``log()``
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directly to print and format help text
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+ if ``Pass::help()`` is not overridden then a default message about missing
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help will be displayed
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.. literalinclude:: /generated/chformal.log
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:lines: 2-
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RST generated from autocmd
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~~~~~~~~~~~~~~~~~~~~~~~~~~
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- below is the raw RST output from ``autocmd`` (``YosysCmdDocumenter`` class in
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:file:`docs/util/cmd_documenter.py`) for `chformal` command
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- heading will be rendered as a subheading of the most recent heading (see
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`chformal autocmd`_ above rendered under `Command help`_)
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- ``.. cmd:def:: <cmd>`` line is indexed for cross references with ``:cmd:ref:``
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directive (`chformal autocmd`_ above uses ``:noindex:`` option so that
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`chformal` still links to the correct location)
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+ ``:title:`` option controls text that appears when hovering over the
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`chformal` link
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- commands with warning flags (experimental or internal) add a ``.. warning``
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block before any of the help content
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- if a command has no ``source_location`` the ``.. note`` at the bottom will
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instead link to :doc:`/cmd/index_other`
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.. autocmd_rst:: chformal
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Cell help
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---------
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- :file:`techlibs/common/simcells.v` and :file:`techlibs/common/simlib.v`
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- parsed by :file:`techlibs/common/cellhelp.py`
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- comments preceding cell type converted to a ``SimHelper`` struct, defined in
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:file:`kernel/register.cc`
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- ``#include``\ d in :file:`kernel/register.cc`, creating a map of cell types to
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their ``SimHelper`` struct.
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- ``help -cells``
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- lists all cells with their input/output ports
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- ``help <celltype>``
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- prints help message for ``<celltype>``
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- constructed from ``SimHelper`` content depending on version
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- ``help <celltype>+``
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- prints verilog code for ``<celltype>``
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v1 (default)
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~~~~~~~~~~~~
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- Legacy format
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- Expects formatting as follows:
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.. code-block:: verilog
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//-
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//- $<celltype> (<ports>)
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//* group <cellgroup>
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//-
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//- <cell description>
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//-
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module \$<celltype> (<ports>);
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// ...
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endmodule
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- ``//* group`` line is generally after the cell signature, but can appear
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anywhere in the comment block
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- determines where the cell is included in sphinx
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- check :file:`docs/source/cell` for current groups
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- a missing group will raise an error
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- assigning an unused group will result in the cell not being included in the
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sphinx docs
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- the port signature line (``//- $<celltype> (<ports>)``) must start with (at
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least) 4 spaces (not tabs)
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- the empty lines (``//-``) before/after the signature are required
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- cell description can be multiple lines, but each line must start with ``//-``
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and a space
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- description should have a trailing empty line
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- line breaks are preserved in `help` calls but will be rendered as text in
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sphinx docs, with empty lines being required between paragraphs
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- cells in :file:`techlibs/common/simcells.v` can have optional truth table at
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the end of the cell description which is rendered in sphinx docs as a literal
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code block
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- e.g. `$_NOT_`:
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.. code-block:: verilog
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//-
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//- $_NOT_ (A, Y)
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//* group comb_simple
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//-
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//- An inverter gate.
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//-
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//- Truth table: A | Y
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//- ---+---
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//- 0 | 1
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//- 1 | 0
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//-
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v2 (more expressive)
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~~~~~~~~~~~~~~~~~~~~
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- each field of the ``SimHelper`` struct can be assigned with:
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.. code-block:: verilog
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//* <name> <value>
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- ``ver`` must be explicitly set as ``2``
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- optional fields ``title`` and ``tags``
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- title used for better displaying of cell
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- tags is a space-separated list of :doc:`/cell/properties`
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- the port signature is automatically generated from the ``module`` definition
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- cell description is the same as v1
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- can link to commands or passes using backticks (`````)
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- e.g. `$nex`:
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.. code-block:: verilog
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//* ver 2
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//* title Case inequality
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//* group binary
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//* tags x-aware
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//- This corresponds to the Verilog '!==' operator.
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//-
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//- Refer to `$eqx` for more details.
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//-
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- code blocks can be included as following:
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.. code-block:: verilog
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//- text
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//- ::
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//-
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//- monospaced text
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//-
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//- indentation and line length will be preserved, giving a scroll bar if necessary for the browser window
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//-
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//- more text
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- the empty line after the ``::`` and before the text continues are required
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- the ``::`` line will be ignored in the `help` call while sphinx docs will
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treat everything that follows as a literal block until the next unindented
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line:
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text
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::
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monospaced text
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indentation and line length will be preserved, giving a scroll bar if necessary for the browser window
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more text
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