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Merge pull request #4731 from YosysHQ/docs-preview-noguidelines 

Integrate guidelines folder into documentation
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128
CODE_OF_CONDUCT.md Normal file
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@ -0,0 +1,128 @@
# Contributor Covenant Code of Conduct
## Our Pledge
We as members, contributors, and leaders pledge to make participation in our
community a harassment-free experience for everyone, regardless of age, body
size, visible or invisible disability, ethnicity, sex characteristics, gender
identity and expression, level of experience, education, socio-economic status,
nationality, personal appearance, race, religion, or sexual identity
and orientation.
We pledge to act and interact in ways that contribute to an open, welcoming,
diverse, inclusive, and healthy community.
## Our Standards
Examples of behavior that contributes to a positive environment for our
community include:
* Demonstrating empathy and kindness toward other people
* Being respectful of differing opinions, viewpoints, and experiences
* Giving and gracefully accepting constructive feedback
* Accepting responsibility and apologizing to those affected by our mistakes,
and learning from the experience
* Focusing on what is best not just for us as individuals, but for the
overall community
Examples of unacceptable behavior include:
* The use of sexualized language or imagery, and sexual attention or
advances of any kind
* Trolling, insulting or derogatory comments, and personal or political attacks
* Public or private harassment
* Publishing others' private information, such as a physical or email
address, without their explicit permission
* Other conduct which could reasonably be considered inappropriate in a
professional setting
## Enforcement Responsibilities
Community leaders are responsible for clarifying and enforcing our standards of
acceptable behavior and will take appropriate and fair corrective action in
response to any behavior that they deem inappropriate, threatening, offensive,
or harmful.
Community leaders have the right and responsibility to remove, edit, or reject
comments, commits, code, wiki edits, issues, and other contributions that are
not aligned to this Code of Conduct, and will communicate reasons for moderation
decisions when appropriate.
## Scope
This Code of Conduct applies within all community spaces, and also applies when
an individual is officially representing the community in public spaces.
Examples of representing our community include using an official e-mail address,
posting via an official social media account, or acting as an appointed
representative at an online or offline event.
## Enforcement
Instances of abusive, harassing, or otherwise unacceptable behavior may be
reported by contacting the project team at contact@yosyshq.com and/or
claire@clairexen.net.
All complaints will be reviewed and investigated promptly and fairly.
All community leaders are obligated to respect the privacy and security of the
reporter of any incident.
## Enforcement Guidelines
Community leaders will follow these Community Impact Guidelines in determining
the consequences for any action they deem in violation of this Code of Conduct:
### 1. Correction
**Community Impact**: Use of inappropriate language or other behavior deemed
unprofessional or unwelcome in the community.
**Consequence**: A private, written warning from community leaders, providing
clarity around the nature of the violation and an explanation of why the
behavior was inappropriate. A public apology may be requested.
### 2. Warning
**Community Impact**: A violation through a single incident or series
of actions.
**Consequence**: A warning with consequences for continued behavior. No
interaction with the people involved, including unsolicited interaction with
those enforcing the Code of Conduct, for a specified period of time. This
includes avoiding interactions in community spaces as well as external channels
like social media. Violating these terms may lead to a temporary or
permanent ban.
### 3. Temporary Ban
**Community Impact**: A serious violation of community standards, including
sustained inappropriate behavior.
**Consequence**: A temporary ban from any sort of interaction or public
communication with the community for a specified period of time. No public or
private interaction with the people involved, including unsolicited interaction
with those enforcing the Code of Conduct, is allowed during this period.
Violating these terms may lead to a permanent ban.
### 4. Permanent Ban
**Community Impact**: Demonstrating a pattern of violation of community
standards, including sustained inappropriate behavior, harassment of an
individual, or aggression toward or disparagement of classes of individuals.
**Consequence**: A permanent ban from any sort of public interaction within
the community.
## Attribution
This Code of Conduct is adapted from the [Contributor Covenant][homepage],
version 2.0, available at
https://www.contributor-covenant.org/version/2/0/code_of_conduct.html.
Community Impact Guidelines were inspired by [Mozilla's code of conduct
enforcement ladder](https://github.com/mozilla/diversity).
[homepage]: https://www.contributor-covenant.org
For answers to common questions about this code of conduct, see the FAQ at
https://www.contributor-covenant.org/faq. Translations are available at
https://www.contributor-covenant.org/translations.

9
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@ -996,15 +996,12 @@ docs/source/cell/word_add.rst: $(TARGETS) $(EXTRA_TARGETS)
docs/source/generated/cells.json: docs/source/generated $(TARGETS) $(EXTRA_TARGETS)
$(Q) ./$(PROGRAM_PREFIX)yosys -p 'help -dump-cells-json $@'
PHONY: docs/gen docs/guidelines docs/usage docs/reqs
PHONY: docs/gen docs/usage docs/reqs
docs/gen: $(TARGETS)
$(Q) $(MAKE) -C docs gen
DOCS_GUIDELINE_FILES := GettingStarted CodingStyle
DOCS_GUIDELINE_SOURCE := $(addprefix guidelines/,$(DOCS_GUIDELINE_FILES))
docs/guidelines docs/source/generated: $(DOCS_GUIDELINE_SOURCE)
docs/source/generated:
$(Q) mkdir -p docs/source/generated
$(Q) cp -f $(DOCS_GUIDELINE_SOURCE) docs/source/generated
# some commands return an error and print the usage text to stderr
define DOC_USAGE_STDERR
@ -1034,7 +1031,7 @@ docs/reqs:
$(Q) $(MAKE) -C docs reqs
.PHONY: docs/prep
docs/prep: docs/source/cmd/abc.rst docs/source/generated/cells.json docs/gen docs/guidelines docs/usage
docs/prep: docs/source/cmd/abc.rst docs/source/generated/cells.json docs/gen docs/usage
DOC_TARGET ?= html
docs: docs/prep

478
README.md
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@ -1,22 +1,3 @@
```
yosys -- Yosys Open SYnthesis Suite
Copyright (C) 2012 - 2024 Claire Xenia Wolf <claire@yosyshq.com>
Permission to use, copy, modify, and/or distribute this software for any
purpose with or without fee is hereby granted, provided that the above
copyright notice and this permission notice appear in all copies.
THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
```
yosys – Yosys Open SYnthesis Suite
===================================
@ -37,23 +18,21 @@ Third-party software distributed alongside this software
is licensed under compatible licenses.
Please refer to `abc` and `libs` subdirectories for their license terms.
Web Site and Other Resources
============================
More information and documentation can be found on the Yosys web site:
- https://yosyshq.net/yosys/
The "Documentation" page on the web site contains links to more resources,
including a manual that even describes some of the Yosys internals:
- https://yosyshq.net/yosys/documentation.html
Documentation from this repository is automatically built and available on Read
the Docs:
- https://yosyshq.readthedocs.io/projects/yosys
The directory `guidelines` contains additional information
for people interested in using the Yosys C++ APIs.
Users interested in formal verification might want to use the formal verification
front-end for Yosys, SymbiYosys:
- https://symbiyosys.readthedocs.io/en/latest/
- https://github.com/YosysHQ/SymbiYosys
Users interested in formal verification might want to use the formal
verification front-end for Yosys, SBY:
- https://yosyshq.readthedocs.io/projects/sby/
- https://github.com/YosysHQ/sby
Installation
@ -71,9 +50,25 @@ For more information about the difference between Tabby CAD Suite and the OSS CA
Many Linux distributions also provide Yosys binaries, some more up to date than others. Check with your package manager!
Building from Source
====================
For more details, and instructions for other platforms, check [building from
source](https://yosyshq.readthedocs.io/projects/yosys/en/latest/getting_started/installation.html#building-from-source)
on Read the Docs.
When cloning Yosys, some required libraries are included as git submodules. Make
sure to call e.g.
$ git clone --recurse-submodules https://github.com/YosysHQ/yosys.git
or
$ git clone https://github.com/YosysHQ/yosys.git
$ cd yosys
$ git submodule update --init --recursive
You need a C++ compiler with C++17 support (up-to-date CLANG or GCC is
recommended) and some standard tools such as GNU Flex, GNU Bison, and GNU Make.
TCL, readline and libffi are optional (see ``ENABLE_*`` settings in Makefile).
@ -87,58 +82,22 @@ prerequisites for building yosys:
graphviz xdot pkg-config python3 libboost-system-dev \
libboost-python-dev libboost-filesystem-dev zlib1g-dev
Similarily, on Mac OS X Homebrew can be used to install dependencies (from within cloned yosys repository):
$ brew tap Homebrew/bundle && brew bundle
or MacPorts:
$ sudo port install bison flex readline gawk libffi \
git graphviz pkgconfig python36 boost zlib tcl
On FreeBSD use the following command to install all prerequisites:
# pkg install bison flex readline gawk libffi\
git graphviz pkgconf python3 python36 tcl-wrapper boost-libs
On FreeBSD system use gmake instead of make. To run tests use:
% MAKE=gmake CC=cc gmake test
For Cygwin use the following command to install all prerequisites, or select these additional packages:
setup-x86_64.exe -q --packages=bison,flex,gcc-core,gcc-g++,git,libffi-devel,libreadline-devel,make,pkg-config,python3,tcl-devel,boost-build,zlib-devel
The environment variable `CXX` can be used to control the C++ compiler used, or
run one of the following:
run one of the following to override it:
$ make config-clang
$ make config-gcc
Note that these will result in `make` ignoring the `CXX` environment variable,
unless `CXX` is assigned in the call to make, e.g.
The Makefile has many variables influencing the build process. These can be
adjusted by modifying the Makefile.conf file which is created at the `make
config-...` step (see above), or they can be set by passing an option to the
make command directly:
$ make CXX=$CXX
The Makefile has many variables influencing the build process. These can be
adjusted by modifying the Makefile.conf file which is created at the
`make config-...` step (see above), or they can be set by passing an option
to the make command directly.
For example, if you have clang, and (a compatible version of) `ld.lld`
available in PATH, it's recommended to speed up incremental builds with
lld by enabling LTO:
$ make ENABLE_LTO=1
On macOS, LTO requires using clang from homebrew which isn't in PATH
rather than xcode clang.
$ make ENABLE_LTO=1 CXX=$(brew --prefix)/opt/llvm/bin/clang++
For other compilers and build configurations it might be
necessary to make some changes to the config section of the
Makefile. It's also an alternative way to set the make variables
mentioned above.
For other compilers and build configurations it might be necessary to make some
changes to the config section of the Makefile. It's also an alternative way to
set the make variables mentioned above.
$ vi Makefile # ..or..
$ vi Makefile.conf
@ -148,10 +107,9 @@ To build Yosys simply type 'make' in this directory.
$ make
$ sudo make install
Note that this also downloads, builds and installs ABC (using yosys-abc
as executable name).
Tests are located in the tests subdirectory and can be executed using the test target. Note that you need gawk as well as a recent version of iverilog (i.e. build from git). Then, execute tests via:
Tests are located in the tests subdirectory and can be executed using the test
target. Note that you need gawk as well as a recent version of iverilog (i.e.
build from git). Then, execute tests via:
$ make test
@ -162,6 +120,7 @@ To use a separate (out-of-tree) build directory, provide a path to the Makefile.
Out-of-tree builds require a clean source tree.
Getting Started
===============
@ -276,371 +235,6 @@ source with another tool such as
``verilator --lint-only``.
Unsupported Verilog-2005 Features
=================================
The following Verilog-2005 features are not supported by
Yosys and there are currently no plans to add support
for them:
- Non-synthesizable language features as defined in
IEC 62142(E):2005 / IEEE Std. 1364.1(E):2002
- The ``tri``, ``triand`` and ``trior`` net types
- The ``config`` and ``disable`` keywords and library map files
Verilog Attributes and non-standard features
============================================
- The ``full_case`` attribute on case statements is supported
(also the non-standard ``// synopsys full_case`` directive)
- The ``parallel_case`` attribute on case statements is supported
(also the non-standard ``// synopsys parallel_case`` directive)
- The ``// synopsys translate_off`` and ``// synopsys translate_on``
directives are also supported (but the use of ``` `ifdef .. `endif ```
is strongly recommended instead).
- The ``nomem2reg`` attribute on modules or arrays prohibits the
automatic early conversion of arrays to separate registers. This
is potentially dangerous. Usually the front-end has good reasons
for converting an array to a list of registers. Prohibiting this
step will likely result in incorrect synthesis results.
- The ``mem2reg`` attribute on modules or arrays forces the early
conversion of arrays to separate registers.
- The ``nomeminit`` attribute on modules or arrays prohibits the
creation of initialized memories. This effectively puts ``mem2reg``
on all memories that are written to in an ``initial`` block and
are not ROMs.
- The ``nolatches`` attribute on modules or always-blocks
prohibits the generation of logic-loops for latches. Instead
all not explicitly assigned values default to x-bits. This does
not affect clocked storage elements such as flip-flops.
- The ``nosync`` attribute on registers prohibits the generation of a
storage element. The register itself will always have all bits set
to 'x' (undefined). The variable may only be used as blocking assigned
temporary variable within an always block. This is mostly used internally
by Yosys to synthesize Verilog functions and access arrays.
- The ``nowrshmsk`` attribute on a register prohibits the generation of
shift-and-mask type circuits for writing to bit slices of that register.
- The ``onehot`` attribute on wires mark them as one-hot state register. This
is used for example for memory port sharing and set by the fsm_map pass.
- The ``blackbox`` attribute on modules is used to mark empty stub modules
that have the same ports as the real thing but do not contain information
on the internal configuration. This modules are only used by the synthesis
passes to identify input and output ports of cells. The Verilog backend
also does not output blackbox modules on default. ``read_verilog``, unless
called with ``-noblackbox`` will automatically set the blackbox attribute
on any empty module it reads.
- The ``noblackbox`` attribute set on an empty module prevents ``read_verilog``
from automatically setting the blackbox attribute on the module.
- The ``whitebox`` attribute on modules triggers the same behavior as
``blackbox``, but is for whitebox modules, i.e. library modules that
contain a behavioral model of the cell type.
- The ``lib_whitebox`` attribute overwrites ``whitebox`` when ``read_verilog``
is run in `-lib` mode. Otherwise it's automatically removed.
- The ``dynports`` attribute is used by the Verilog front-end to mark modules
that have ports with a width that depends on a parameter.
- The ``hdlname`` attribute is used by some passes to document the original
(HDL) name of a module when renaming a module. It should contain a single
name, or, when describing a hierarchical name in a flattened design, multiple
names separated by a single space character.
- The ``keep`` attribute on cells and wires is used to mark objects that should
never be removed by the optimizer. This is used for example for cells that
have hidden connections that are not part of the netlist, such as IO pads.
Setting the ``keep`` attribute on a module has the same effect as setting it
on all instances of the module.
- The ``keep_hierarchy`` attribute on cells and modules keeps the ``flatten``
command from flattening the indicated cells and modules.
- The `gate_cost_equivalent` attribute on a module can be used to specify
the estimated cost of the module as a number of basic gate instances. See
the help message of command `keep_hierarchy` which interprets this
attribute.
- The ``init`` attribute on wires is set by the frontend when a register is
initialized "FPGA-style" with ``reg foo = val``. It can be used during
synthesis to add the necessary reset logic.
- The ``top`` attribute on a module marks this module as the top of the
design hierarchy. The ``hierarchy`` command sets this attribute when called
with ``-top``. Other commands, such as ``flatten`` and various backends
use this attribute to determine the top module.
- The ``src`` attribute is set on cells and wires created by to the string
``<hdl-file-name>:<line-number>`` by the HDL front-end and is then carried
through the synthesis. When entities are combined, a new |-separated
string is created that contains all the string from the original entities.
- The ``defaultvalue`` attribute is used to store default values for
module inputs. The attribute is attached to the input wire by the HDL
front-end when the input is declared with a default value.
- The ``parameter`` and ``localparam`` attributes are used to mark wires
that represent module parameters or localparams (when the HDL front-end
is run in ``-pwires`` mode).
- Wires marked with the ``hierconn`` attribute are connected to wires with the
same name (format ``cell_name.identifier``) when they are imported from
sub-modules by ``flatten``.
- The ``clkbuf_driver`` attribute can be set on an output port of a blackbox
module to mark it as a clock buffer output, and thus prevent ``clkbufmap``
from inserting another clock buffer on a net driven by such output.
- The ``clkbuf_sink`` attribute can be set on an input port of a module to
request clock buffer insertion by the ``clkbufmap`` pass.
- The ``clkbuf_inv`` attribute can be set on an output port of a module
with the value set to the name of an input port of that module. When
the ``clkbufmap`` would otherwise insert a clock buffer on this output,
it will instead try inserting the clock buffer on the input port (this
is used to implement clock inverter cells that clock buffer insertion
will "see through").
- The ``clkbuf_inhibit`` is the default attribute to set on a wire to prevent
automatic clock buffer insertion by ``clkbufmap``. This behaviour can be
overridden by providing a custom selection to ``clkbufmap``.
- The ``invertible_pin`` attribute can be set on a port to mark it as
invertible via a cell parameter. The name of the inversion parameter
is specified as the value of this attribute. The value of the inversion
parameter must be of the same width as the port, with 1 indicating
an inverted bit and 0 indicating a non-inverted bit.
- The ``iopad_external_pin`` attribute on a blackbox module's port marks
it as the external-facing pin of an I/O pad, and prevents ``iopadmap``
from inserting another pad cell on it.
- The module attribute ``abc9_lut`` is an integer attribute indicating to
`abc9` that this module describes a LUT with an area cost of this value, and
propagation delays described using `specify` statements.
- The module attribute ``abc9_box`` is a boolean specifying a black/white-box
definition, with propagation delays described using `specify` statements, for
use by `abc9`.
- The port attribute ``abc9_carry`` marks the carry-in (if an input port) and
carry-out (if output port) ports of a box. This information is necessary for
`abc9` to preserve the integrity of carry-chains. Specifying this attribute
onto a bus port will affect only its most significant bit.
- The module attribute ``abc9_flop`` is a boolean marking the module as a
flip-flop. This allows `abc9` to analyse its contents in order to perform
sequential synthesis.
- The frontend sets attributes ``always_comb``, ``always_latch`` and
``always_ff`` on processes derived from SystemVerilog style always blocks
according to the type of the always. These are checked for correctness in
``proc_dlatch``.
- The cell attribute ``wildcard_port_conns`` represents wildcard port
connections (SystemVerilog ``.*``). These are resolved to concrete
connections to matching wires in ``hierarchy``.
- In addition to the ``(* ... *)`` attribute syntax, Yosys supports
the non-standard ``{* ... *}`` attribute syntax to set default attributes
for everything that comes after the ``{* ... *}`` statement. (Reset
by adding an empty ``{* *}`` statement.)
- In module parameter and port declarations, and cell port and parameter
lists, a trailing comma is ignored. This simplifies writing Verilog code
generators a bit in some cases.
- Modules can be declared with ``module mod_name(...);`` (with three dots
instead of a list of module ports). With this syntax it is sufficient
to simply declare a module port as 'input' or 'output' in the module
body.
- When defining a macro with `define, all text between triple double quotes
is interpreted as macro body, even if it contains unescaped newlines. The
triple double quotes are removed from the macro body. For example:
`define MY_MACRO(a, b) """
assign a = 23;
assign b = 42;
"""
- The attribute ``via_celltype`` can be used to implement a Verilog task or
function by instantiating the specified cell type. The value is the name
of the cell type to use. For functions the name of the output port can
be specified by appending it to the cell type separated by a whitespace.
The body of the task or function is unused in this case and can be used
to specify a behavioral model of the cell type for simulation. For example:
module my_add3(A, B, C, Y);
parameter WIDTH = 8;
input [WIDTH-1:0] A, B, C;
output [WIDTH-1:0] Y;
...
endmodule
module top;
...
(* via_celltype = "my_add3 Y" *)
(* via_celltype_defparam_WIDTH = 32 *)
function [31:0] add3;
input [31:0] A, B, C;
begin
add3 = A + B + C;
end
endfunction
...
endmodule
- The ``wiretype`` attribute is added by the verilog parser for wires of a
typedef'd type to indicate the type identifier.
- Various ``enum_value_{value}`` attributes are added to wires of an enumerated type
to give a map of possible enum items to their values.
- The ``enum_base_type`` attribute is added to enum items to indicate which
enum they belong to (enums -- anonymous and otherwise -- are
automatically named with an auto-incrementing counter). Note that enums
are currently not strongly typed.
- A limited subset of DPI-C functions is supported. The plugin mechanism
(see ``help plugin``) can be used to load .so files with implementations
of DPI-C routines. As a non-standard extension it is possible to specify
a plugin alias using the ``<alias>:`` syntax. For example:
module dpitest;
import "DPI-C" function foo:round = real my_round (real);
parameter real r = my_round(12.345);
endmodule
$ yosys -p 'plugin -a foo -i /lib/libm.so; read_verilog dpitest.v'
- Sized constants (the syntax ``<size>'s?[bodh]<value>``) support constant
expressions as ``<size>``. If the expression is not a simple identifier, it
must be put in parentheses. Examples: ``WIDTH'd42``, ``(4+2)'b101010``
- The system tasks ``$finish``, ``$stop`` and ``$display`` are supported in
initial blocks in an unconditional context (only if/case statements on
expressions over parameters and constant values are allowed). The intended
use for this is synthesis-time DRC.
- There is limited support for converting ``specify`` .. ``endspecify``
statements to special ``$specify2``, ``$specify3``, and ``$specrule`` cells,
for use in blackboxes and whiteboxes. Use ``read_verilog -specify`` to
enable this functionality. (By default these blocks are ignored.)
- The ``reprocess_after`` internal attribute is used by the Verilog frontend to
mark cells with bindings which might depend on the specified instantiated
module. Modules with such cells will be reprocessed during the ``hierarchy``
pass once the referenced module definition(s) become available.
- The ``smtlib2_module`` attribute can be set on a blackbox module to specify a
formal model directly using SMT-LIB 2. For such a module, the
``smtlib2_comb_expr`` attribute can be used on output ports to define their
value using an SMT-LIB 2 expression. For example:
(* blackbox *)
(* smtlib2_module *)
module submod(a, b);
input [7:0] a;
(* smtlib2_comb_expr = "(bvnot a)" *)
output [7:0] b;
endmodule
Non-standard or SystemVerilog features for formal verification
==============================================================
- Support for ``assert``, ``assume``, ``restrict``, and ``cover`` is enabled
when ``read_verilog`` is called with ``-formal``.
- The system task ``$initstate`` evaluates to 1 in the initial state and
to 0 otherwise.
- The system function ``$anyconst`` evaluates to any constant value. This is
equivalent to declaring a reg as ``rand const``, but also works outside
of checkers. (Yosys also supports ``rand const`` outside checkers.)
- The system function ``$anyseq`` evaluates to any value, possibly a different
value in each cycle. This is equivalent to declaring a reg as ``rand``,
but also works outside of checkers. (Yosys also supports ``rand``
variables outside checkers.)
- The system functions ``$allconst`` and ``$allseq`` can be used to construct
formal exist-forall problems. Assumptions only hold if the trace satisfies
the assumption for all ``$allconst/$allseq`` values. For assertions and cover
statements it is sufficient if just one ``$allconst/$allseq`` value triggers
the property (similar to ``$anyconst/$anyseq``).
- Wires/registers declared using the ``anyconst/anyseq/allconst/allseq`` attribute
(for example ``(* anyconst *) reg [7:0] foobar;``) will behave as if driven
by a ``$anyconst/$anyseq/$allconst/$allseq`` function.
- The SystemVerilog tasks ``$past``, ``$stable``, ``$rose`` and ``$fell`` are
supported in any clocked block.
- The syntax ``@($global_clock)`` can be used to create FFs that have no
explicit clock input (``$ff`` cells). The same can be achieved by using
``@(posedge <netname>)`` or ``@(negedge <netname>)`` when ``<netname>``
is marked with the ``(* gclk *)`` Verilog attribute.
Supported features from SystemVerilog
=====================================
When ``read_verilog`` is called with ``-sv``, it accepts some language features
from SystemVerilog:
- The ``assert`` statement from SystemVerilog is supported in its most basic
form. In module context: ``assert property (<expression>);`` and within an
always block: ``assert(<expression>);``. It is transformed to an ``$assert`` cell.
- The ``assume``, ``restrict``, and ``cover`` statements from SystemVerilog are
also supported. The same limitations as with the ``assert`` statement apply.
- The keywords ``always_comb``, ``always_ff`` and ``always_latch``, ``logic``
and ``bit`` are supported.
- Declaring free variables with ``rand`` and ``rand const`` is supported.
- Checkers without a port list that do not need to be instantiated (but instead
behave like a named block) are supported.
- SystemVerilog packages are supported. Once a SystemVerilog file is read
into a design with ``read_verilog``, all its packages are available to
SystemVerilog files being read into the same design afterwards.
- typedefs are supported (including inside packages)
- type casts are currently not supported
- enums are supported (including inside packages)
- but are currently not strongly typed
- packed structs and unions are supported
- arrays of packed structs/unions are currently not supported
- structure literals are currently not supported
- multidimensional arrays are supported
- array assignment of unpacked arrays is currently not supported
- array literals are currently not supported
- SystemVerilog interfaces (SVIs) are supported. Modports for specifying whether
ports are inputs or outputs are supported.
- Assignments within expressions are supported.
Building the documentation
==========================

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@ -62,9 +62,25 @@ The `OSS CAD Suite`_ releases `nightly builds`_ for the following architectures:
Building from source
~~~~~~~~~~~~~~~~~~~~
Refer to the `readme`_ for the most up-to-date install instructions.
The Yosys source files can be obtained from the `YosysHQ/Yosys git repository`_.
`ABC`_ and some of the other libraries used are included as git submodules. To
clone these submodules at the same time, use e.g.:
.. _readme: https://github.com/YosysHQ/yosys#building-from-source
.. code:: console
git clone --recurse-submodules https://github.com/YosysHQ/yosys.git # ..or..
git clone https://github.com/YosysHQ/yosys.git
cd yosys
git submodule update --init --recursive
.. _YosysHQ/Yosys git repository: https://github.com/yosyshq/yosys/
.. _ABC: https://github.com/berkeley-abc/abc
.. note::
As of Yosys v0.47, releases include a ``yosys.tar.gz`` file which includes
all source code and all sub-modules in a single archive. This can be used as
an alternative which does not rely on ``git``.
Supported platforms
^^^^^^^^^^^^^^^^^^^
@ -94,17 +110,116 @@ Installing all prerequisites for Ubuntu 20.04:
.. code:: console
sudo sudo apt-get install build-essential clang lld bison flex \
libreadline-dev gawk tcl-dev libffi-dev git make \
graphviz xdot pkg-config python3 libboost-system-dev \
sudo apt-get install gperf build-essential bison flex \
libreadline-dev gawk tcl-dev libffi-dev git graphviz \
xdot pkg-config python3 libboost-system-dev \
libboost-python-dev libboost-filesystem-dev zlib1g-dev
Installing all prerequisites for macOS 11 (with Homebrew):
Installing all prerequisites for macOS 13 (with Homebrew):
.. code:: console
brew install bison flex gawk libffi git graphviz \
pkg-config python3 tcl-tk xdot bash boost-python3
brew tap Homebrew/bundle && brew bundle
or MacPorts:
.. code:: console
sudo port install bison flex readline gawk libffi graphviz \
pkgconfig python311 boost zlib tcl
On FreeBSD use the following command to install all prerequisites:
.. code:: console
pkg install bison flex readline gawk libffi graphviz \
pkgconf python311 tcl-wrapper boost-libs
.. note:: On FreeBSD system use gmake instead of make. To run tests use:
``MAKE=gmake CXX=cxx CC=cc gmake test``
For Cygwin use the following command to install all prerequisites, or select these additional packages:
.. code:: console
setup-x86_64.exe -q --packages=bison,flex,gcc-core,gcc-g++,git,libffi-devel,libreadline-devel,make,pkg-config,python3,tcl-devel,boost-build,zlib-devel
.. warning::
As of this writing, Cygwin only supports up to Python 3.9.16 while the
minimum required version of Python is 3.11. This means that Cygwin is not
compatible with many of the Python-based frontends. While this does not
currently prevent Yosys itself from working, no guarantees are made for
continued support. It is instead recommended to use Windows Subsystem for
Linux (WSL) and follow the instructions for Ubuntu.
..
For MSYS2 (MINGW64):
.. code:: console
pacman -S bison flex mingw-w64-x86_64-gcc git libffi-devel libreadline-devel make pkg-config python3 tcl-devel mingw-w64-x86_64-boost zlib-devel
Not that I can get this to work; it's failing during ld with what looks like
math library issues: ``multiple definition of `tanh'`` and
``undefined reference to `__imp_acosh'``, as well as issues in `aiger2` with
``seekg`` et al not being available.
.. note::
The ``config-msys2-64`` target uses the ``mingw-w64-x86_64-`` prefixed
compiler in order to allow compiled exe files to be run without an MSYS2
shell.
Build configuration
^^^^^^^^^^^^^^^^^^^
The Yosys build is based solely on Makefiles, and uses a number of variables
which influence the build process. The recommended method for configuring
builds is with a ``Makefile.conf`` file in the root ``yosys`` directory. The
following commands will clean the directory and provide an initial configuration
file:
.. code:: console
make config-clang # ..or..
make config-gcc
Check the root Makefile to see what other configuration targets are available.
Other variables can then be added to the ``Makefile.conf`` as needed, for
example:
.. code:: console
echo "ENABLE_ZLIB := 0" >> Makefile.conf
Using one of these targets will set the ``CONFIG`` variable to something other
than ``none``, and will override the environment variable for ``CXX``. To use a
different compiler than the default when building, use:
.. code:: console
make CXX=$CXX # ..or..
make CXX="g++-11"
.. note::
Setting the compiler in this way will prevent some other options such as
``ENABLE_CCACHE`` from working as expected.
If you have clang, and (a compatible version of) ``ld.lld`` available in PATH,
it's recommended to speed up incremental builds with lld by enabling LTO with
``ENABLE_LTO=1``. On macOS, LTO requires using clang from homebrew rather than
clang from xcode. For example:
.. code:: console
make ENABLE_LTO=1 CXX=$(brew --prefix)/opt/llvm/bin/clang++
By default, building (and installing) yosys will build (and install) `ABC`_,
using :program:`yosys-abc` as the executable name. To use an existing ABC
executable instead, set the ``ABCEXTERNAL`` make variable to point to the
desired executable.
Running the build system
^^^^^^^^^^^^^^^^^^^^^^^^
@ -116,25 +231,14 @@ From the root ``yosys`` directory, call the following commands:
make
sudo make install
This will build and then install Yosys, making it available on the command line
as ``yosys``. Note that this also downloads, builds, and installs `ABC`_ (using
:program:`yosys-abc` as the executable name).
.. _ABC: https://github.com/berkeley-abc/abc
The default compiler is ``clang``, to change between ``clang`` and ``gcc``, use
one of the following:
To use a separate (out-of-tree) build directory, provide a path to the Makefile.
.. code:: console
make config-clang
make config-gcc
mkdir build; cd build
make -f ../Makefile
To use a compiler different than the default, use:
.. code:: console
make CXX="g++-11"
Out-of-tree builds require a clean source tree.
.. seealso::
@ -161,10 +265,6 @@ directories:
``frontends/``
This directory contains a subdirectory for each of the frontend modules.
``guidelines/``
Contains developer guidelines, including the code of conduct and coding style
guide.
``kernel/``
This directory contains all the core functionality of Yosys. This includes
the functions and definitions for working with the RTLIL data structures
@ -206,9 +306,6 @@ commands.
Good starting points for reading example source code to learn how to write
passes are :file:`passes/opt/opt_dff.cc` and :file:`passes/opt/opt_merge.cc`.
See the top-level README file for a quick Getting Started guide and build
instructions. The Yosys build is based solely on Makefiles.
Users of the Qt Creator IDE can generate a QT Creator project file using make
qtcreator. Users of the Eclipse IDE can use the "Makefile Project with Existing
Code" project type in the Eclipse "New Project" dialog (only available after the

36
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@ -0,0 +1,36 @@
Contributing to Yosys
=====================
Coding Style
------------
Formatting of code
~~~~~~~~~~~~~~~~~~
- Yosys code is using tabs for indentation. Tabs are 8 characters.
- A continuation of a statement in the following line is indented by two
additional tabs.
- Lines are as long as you want them to be. A good rule of thumb is to break
lines at about column 150.
- Opening braces can be put on the same or next line as the statement opening
the block (if, switch, for, while, do). Put the opening brace on its own line
for larger blocks, especially blocks that contains blank lines.
- Otherwise stick to the `Linux Kernel Coding Style`_.
.. _Linux Kernel Coding Style: https://www.kernel.org/doc/Documentation/process/coding-style.rst
C++ Language
~~~~~~~~~~~~
Yosys is written in C++17.
In general Yosys uses ``int`` instead of ``size_t``. To avoid compiler warnings
for implicit type casts, always use ``GetSize(foobar)`` instead of
``foobar.size()``. (``GetSize()`` is defined in :file:`kernel/yosys.h`)
Use range-based for loops whenever applicable.

6
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@ -11,11 +11,7 @@ Writing extensions
This chapter contains some bits and pieces of information about programming
yosys extensions. Don't be afraid to ask questions on the YosysHQ Slack.
The :file:`guidelines/` directory of the Yosys source code contains notes on
various aspects of Yosys development. In particular, the files GettingStarted
and CodingStyle may be of interest.
.. todo:: what's in guidelines/GettingStarted that's missing from the manual?
.. todo:: mention coding guide
Quick guide
-----------

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@ -11,5 +11,6 @@ of interest for developers looking to customise Yosys builds.
extensions
build_verific
functional_ir
contributing
test_suites

78
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@ -1,7 +1,7 @@
Testing Yosys
=============
.. todo:: more about the included test suite
.. TODO:: more about the included test suite and how to add tests
Automatic testing
-----------------
@ -23,3 +23,79 @@ For up to date information, including OS versions, refer to `the git actions
page`_.
.. _the git actions page: https://github.com/YosysHQ/yosys/actions
.. todo:: are unit tests currently working
..
How to add a unit test
----------------------
Unit test brings some advantages, briefly, we can list some of them (reference
[1](https://en.wikipedia.org/wiki/Unit_testing)):
* Tests reduce bugs in new features;
* Tests reduce bugs in existing features;
* Tests are good documentation;
* Tests reduce the cost of change;
* Tests allow refactoring;
With those advantages in mind, it was required to choose a framework which fits
well with C/C++ code. Hence, `google test`_ was chosen, because it is widely
used and it is relatively easy learn.
.. _google test: https://github.com/google/googletest
Install and configure google test (manually)
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
In this section, you will see a brief description of how to install google test.
However, it is strongly recommended that you take a look to the official
repository (https://github.com/google/googletest) and refers to that if you have
any problem to install it. Follow the steps below:
* Install: cmake and pthread
* Clone google test project from: https://github.com/google/googletest and enter
in the project directory
* Inside project directory, type:
.. code-block:: console
cmake -DBUILD_SHARED_LIBS=ON .
make
* After compilation, copy all ``*.so`` inside directory ``googlemock`` and
``googlemock/gtest`` to ``/usr/lib/``
* Done! Now you can compile your tests.
If you have any problem, go to the official repository to find help.
Ps.: Some distros already have googletest packed. If your distro supports it,
you can use it instead of compile.
Create a new unit test
~~~~~~~~~~~~~~~~~~~~~~
If you want to add new unit tests for Yosys, just follow the steps below:
* Go to directory :file:`test/unit/`
* In this directory you can find something similar Yosys's directory structure.
To create your unit test file you have to follow this pattern:
fileNameToImplementUnitTest + Test.cc. E.g.: if you want to implement the unit
test for ``kernel/celledges.cc``, you will need to create a file like this:
``tests/unit/kernel/celledgesTest.cc``;
* Implement your unit test
Run unit tests
~~~~~~~~~~~~~~
To compile and run all unit tests, just go to yosys root directory and type:
.. code-block:: console
make unit-test
If you want to remove all unit test files, type:
.. code-block:: console
make clean-unit-test

1
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@ -38,3 +38,4 @@ as reference to implement a similar system in any language.
formats/index
extending_yosys/index
techmap
verilog

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@ -0,0 +1,377 @@
Notes on Verilog support in Yosys
=================================
.. TODO:: how much of this is specific to the read_verilog and should be in :doc:`/yosys_internals/flow/verilog_frontend`?
Unsupported Verilog-2005 Features
---------------------------------
The following Verilog-2005 features are not supported by
Yosys and there are currently no plans to add support
for them:
- Non-synthesizable language features as defined in
IEC 62142(E):2005 / IEEE Std. 1364.1(E):2002
- The ``tri``, ``triand`` and ``trior`` net types
- The ``config`` and ``disable`` keywords and library map files
Verilog Attributes and non-standard features
--------------------------------------------
- The ``full_case`` attribute on case statements is supported (also the
non-standard ``// synopsys full_case`` directive)
- The ``parallel_case`` attribute on case statements is supported (also the
non-standard ``// synopsys parallel_case`` directive)
- The ``// synopsys translate_off`` and ``// synopsys translate_on`` directives
are also supported (but the use of ``` `ifdef .. `endif ``` is strongly
recommended instead).
- The ``nomem2reg`` attribute on modules or arrays prohibits the automatic early
conversion of arrays to separate registers. This is potentially dangerous.
Usually the front-end has good reasons for converting an array to a list of
registers. Prohibiting this step will likely result in incorrect synthesis
results.
- The ``mem2reg`` attribute on modules or arrays forces the early conversion of
arrays to separate registers.
- The ``nomeminit`` attribute on modules or arrays prohibits the creation of
initialized memories. This effectively puts ``mem2reg`` on all memories that
are written to in an ``initial`` block and are not ROMs.
- The ``nolatches`` attribute on modules or always-blocks prohibits the
generation of logic-loops for latches. Instead all not explicitly assigned
values default to x-bits. This does not affect clocked storage elements such
as flip-flops.
- The ``nosync`` attribute on registers prohibits the generation of a storage
element. The register itself will always have all bits set to 'x' (undefined).
The variable may only be used as blocking assigned temporary variable within
an always block. This is mostly used internally by Yosys to synthesize Verilog
functions and access arrays.
- The ``nowrshmsk`` attribute on a register prohibits the generation of
shift-and-mask type circuits for writing to bit slices of that register.
- The ``onehot`` attribute on wires mark them as one-hot state register. This is
used for example for memory port sharing and set by the fsm_map pass.
- The ``blackbox`` attribute on modules is used to mark empty stub modules that
have the same ports as the real thing but do not contain information on the
internal configuration. This modules are only used by the synthesis passes to
identify input and output ports of cells. The Verilog backend also does not
output blackbox modules on default. `read_verilog`, unless called with
``-noblackbox`` will automatically set the blackbox attribute on any empty
module it reads.
- The ``noblackbox`` attribute set on an empty module prevents `read_verilog`
from automatically setting the blackbox attribute on the module.
- The ``whitebox`` attribute on modules triggers the same behavior as
``blackbox``, but is for whitebox modules, i.e. library modules that contain a
behavioral model of the cell type.
- The ``lib_whitebox`` attribute overwrites ``whitebox`` when `read_verilog` is
run in ``-lib`` mode. Otherwise it's automatically removed.
- The ``dynports`` attribute is used by the Verilog front-end to mark modules
that have ports with a width that depends on a parameter.
- The ``hdlname`` attribute is used by some passes to document the original
(HDL) name of a module when renaming a module. It should contain a single
name, or, when describing a hierarchical name in a flattened design, multiple
names separated by a single space character.
- The ``keep`` attribute on cells and wires is used to mark objects that should
never be removed by the optimizer. This is used for example for cells that
have hidden connections that are not part of the netlist, such as IO pads.
Setting the ``keep`` attribute on a module has the same effect as setting it
on all instances of the module.
- The ``keep_hierarchy`` attribute on cells and modules keeps the `flatten`
command from flattening the indicated cells and modules.
- The `gate_cost_equivalent` attribute on a module can be used to specify
the estimated cost of the module as a number of basic gate instances. See
the help message of command `keep_hierarchy` which interprets this
attribute.
- The ``init`` attribute on wires is set by the frontend when a register is
initialized "FPGA-style" with ``reg foo = val``. It can be used during
synthesis to add the necessary reset logic.
- The ``top`` attribute on a module marks this module as the top of the design
hierarchy. The `hierarchy` command sets this attribute when called with
``-top``. Other commands, such as `flatten` and various backends use this
attribute to determine the top module.
- The ``src`` attribute is set on cells and wires created by to the string
``<hdl-file-name>:<line-number>`` by the HDL front-end and is then carried
through the synthesis. When entities are combined, a new \|-separated string
is created that contains all the strings from the original entities.
- The ``defaultvalue`` attribute is used to store default values for module
inputs. The attribute is attached to the input wire by the HDL front-end when
the input is declared with a default value.
- The ``parameter`` and ``localparam`` attributes are used to mark wires that
represent module parameters or localparams (when the HDL front-end is run in
``-pwires`` mode).
- Wires marked with the ``hierconn`` attribute are connected to wires with the
same name (format ``cell_name.identifier``) when they are imported from
sub-modules by `flatten`.
- The ``clkbuf_driver`` attribute can be set on an output port of a blackbox
module to mark it as a clock buffer output, and thus prevent `clkbufmap` from
inserting another clock buffer on a net driven by such output.
- The ``clkbuf_sink`` attribute can be set on an input port of a module to
request clock buffer insertion by the `clkbufmap` pass.
- The ``clkbuf_inv`` attribute can be set on an output port of a module with the
value set to the name of an input port of that module. When the `clkbufmap`
would otherwise insert a clock buffer on this output, it will instead try
inserting the clock buffer on the input port (this is used to implement clock
inverter cells that clock buffer insertion will "see through").
- The ``clkbuf_inhibit`` is the default attribute to set on a wire to prevent
automatic clock buffer insertion by `clkbufmap`. This behaviour can be
overridden by providing a custom selection to `clkbufmap`.
- The ``invertible_pin`` attribute can be set on a port to mark it as invertible
via a cell parameter. The name of the inversion parameter is specified as the
value of this attribute. The value of the inversion parameter must be of the
same width as the port, with 1 indicating an inverted bit and 0 indicating a
non-inverted bit.
- The ``iopad_external_pin`` attribute on a blackbox module's port marks it as
the external-facing pin of an I/O pad, and prevents `iopadmap` from inserting
another pad cell on it.
- The module attribute ``abc9_lut`` is an integer attribute indicating to `abc9`
that this module describes a LUT with an area cost of this value, and
propagation delays described using ``specify`` statements.
- The module attribute ``abc9_box`` is a boolean specifying a black/white-box
definition, with propagation delays described using ``specify`` statements,
for use by `abc9`.
- The port attribute ``abc9_carry`` marks the carry-in (if an input port) and
carry-out (if output port) ports of a box. This information is necessary for
`abc9` to preserve the integrity of carry-chains. Specifying this attribute
onto a bus port will affect only its most significant bit.
- The module attribute ``abc9_flop`` is a boolean marking the module as a
flip-flop. This allows `abc9` to analyse its contents in order to perform
sequential synthesis.
- The frontend sets attributes ``always_comb``, ``always_latch`` and
``always_ff`` on processes derived from SystemVerilog style always blocks
according to the type of the always. These are checked for correctness in
``proc_dlatch``.
- The cell attribute ``wildcard_port_conns`` represents wildcard port
connections (SystemVerilog ``.*``). These are resolved to concrete connections
to matching wires in `hierarchy`.
- In addition to the ``(* ... *)`` attribute syntax, Yosys supports the
non-standard ``{* ... *}`` attribute syntax to set default attributes for
everything that comes after the ``{* ... *}`` statement. (Reset by adding an
empty ``{* *}`` statement.)
- In module parameter and port declarations, and cell port and parameter lists,
a trailing comma is ignored. This simplifies writing Verilog code generators a
bit in some cases.
- Modules can be declared with ``module mod_name(...);`` (with three dots
instead of a list of module ports). With this syntax it is sufficient to
simply declare a module port as 'input' or 'output' in the module body.
- When defining a macro with ``\`define``, all text between triple double quotes
is interpreted as macro body, even if it contains unescaped newlines. The
triple double quotes are removed from the macro body. For example:
.. code-block:: verilog
`define MY_MACRO(a, b) """
assign a = 23;
assign b = 42;
"""
- The attribute ``via_celltype`` can be used to implement a Verilog task or
function by instantiating the specified cell type. The value is the name of
the cell type to use. For functions the name of the output port can be
specified by appending it to the cell type separated by a whitespace. The body
of the task or function is unused in this case and can be used to specify a
behavioral model of the cell type for simulation. For example:
.. code-block:: verilog
module my_add3(A, B, C, Y);
parameter WIDTH = 8;
input [WIDTH-1:0] A, B, C;
output [WIDTH-1:0] Y;
...
endmodule
module top;
...
(* via_celltype = "my_add3 Y" *)
(* via_celltype_defparam_WIDTH = 32 *)
function [31:0] add3;
input [31:0] A, B, C;
begin
add3 = A + B + C;
end
endfunction
...
endmodule
- The ``wiretype`` attribute is added by the verilog parser for wires of a
typedef'd type to indicate the type identifier.
- Various ``enum_value_{value}`` attributes are added to wires of an enumerated
type to give a map of possible enum items to their values.
- The ``enum_base_type`` attribute is added to enum items to indicate which enum
they belong to (enums -- anonymous and otherwise -- are automatically named
with an auto-incrementing counter). Note that enums are currently not strongly
typed.
- A limited subset of DPI-C functions is supported. The plugin mechanism (see
``help plugin``) can be used to load .so files with implementations of DPI-C
routines. As a non-standard extension it is possible to specify a plugin alias
using the ``<alias>:`` syntax. For example:
.. code-block:: verilog
module dpitest;
import "DPI-C" function foo:round = real my_round (real);
parameter real r = my_round(12.345);
endmodule
.. code-block::
$ yosys -p 'plugin -a foo -i /lib/libm.so; read_verilog dpitest.v'
- Sized constants (the syntax ``<size>'s?[bodh]<value>``) support constant
expressions as ``<size>``. If the expression is not a simple identifier, it
must be put in parentheses. Examples: ``WIDTH'd42``, ``(4+2)'b101010``
- The system tasks ``$finish``, ``$stop`` and ``$display`` are supported in
initial blocks in an unconditional context (only if/case statements on
expressions over parameters and constant values are allowed). The intended use
for this is synthesis-time DRC.
- There is limited support for converting ``specify`` .. ``endspecify``
statements to special ``$specify2``, ``$specify3``, and ``$specrule`` cells,
for use in blackboxes and whiteboxes. Use ``read_verilog -specify`` to enable
this functionality. (By default these blocks are ignored.)
- The ``reprocess_after`` internal attribute is used by the Verilog frontend to
mark cells with bindings which might depend on the specified instantiated
module. Modules with such cells will be reprocessed during the `hierarchy`
pass once the referenced module definition(s) become available.
- The ``smtlib2_module`` attribute can be set on a blackbox module to specify a
formal model directly using SMT-LIB 2. For such a module, the
``smtlib2_comb_expr`` attribute can be used on output ports to define their
value using an SMT-LIB 2 expression. For example:
.. code-block:: verilog
(* blackbox *)
(* smtlib2_module *)
module submod(a, b);
input [7:0] a;
(* smtlib2_comb_expr = "(bvnot a)" *)
output [7:0] b;
endmodule
Non-standard or SystemVerilog features for formal verification
--------------------------------------------------------------
- Support for ``assert``, ``assume``, ``restrict``, and ``cover`` is enabled
when `read_verilog` is called with ``-formal``.
- The system task ``$initstate`` evaluates to 1 in the initial state and to 0
otherwise.
- The system function ``$anyconst`` evaluates to any constant value. This is
equivalent to declaring a reg as ``rand const``, but also works outside of
checkers. (Yosys also supports ``rand const`` outside checkers.)
- The system function ``$anyseq`` evaluates to any value, possibly a different
value in each cycle. This is equivalent to declaring a reg as ``rand``, but
also works outside of checkers. (Yosys also supports ``rand`` variables
outside checkers.)
- The system functions ``$allconst`` and ``$allseq`` can be used to construct
formal exist-forall problems. Assumptions only hold if the trace satisfies the
assumption for all ``$allconst/$allseq`` values. For assertions and cover
statements it is sufficient if just one ``$allconst/$allseq`` value triggers
the property (similar to ``$anyconst/$anyseq``).
- Wires/registers declared using the ``anyconst/anyseq/allconst/allseq``
attribute (for example ``(* anyconst *) reg [7:0] foobar;``) will behave as if
driven by a ``$anyconst/$anyseq/$allconst/$allseq`` function.
- The SystemVerilog tasks ``$past``, ``$stable``, ``$rose`` and ``$fell`` are
supported in any clocked block.
- The syntax ``@($global_clock)`` can be used to create FFs that have no
explicit clock input (``$ff`` cells). The same can be achieved by using
``@(posedge <netname>)`` or ``@(negedge <netname>)`` when ``<netname>`` is
marked with the ``(* gclk *)`` Verilog attribute.
Supported features from SystemVerilog
-------------------------------------
When `read_verilog` is called with ``-sv``, it accepts some language features
from SystemVerilog:
- The ``assert`` statement from SystemVerilog is supported in its most basic
form. In module context: ``assert property (<expression>);`` and within an
always block: ``assert(<expression>);``. It is transformed to an ``$assert``
cell.
- The ``assume``, ``restrict``, and ``cover`` statements from SystemVerilog are
also supported. The same limitations as with the ``assert`` statement apply.
- The keywords ``always_comb``, ``always_ff`` and ``always_latch``, ``logic``
and ``bit`` are supported.
- Declaring free variables with ``rand`` and ``rand const`` is supported.
- Checkers without a port list that do not need to be instantiated (but instead
behave like a named block) are supported.
- SystemVerilog packages are supported. Once a SystemVerilog file is read into a
design with `read_verilog`, all its packages are available to SystemVerilog
files being read into the same design afterwards.
- typedefs are supported (including inside packages)
- type casts are currently not supported
- enums are supported (including inside packages)
- but are currently not strongly typed
- packed structs and unions are supported
- arrays of packed structs/unions are currently not supported
- structure literals are currently not supported
- multidimensional arrays are supported
- array assignment of unpacked arrays is currently not supported
- array literals are currently not supported
- SystemVerilog interfaces (SVIs) are supported. Modports for specifying whether
ports are inputs or outputs are supported.
- Assignments within expressions are supported.

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@ -1,116 +0,0 @@
Checklist for adding internal cell types
========================================
Things to do right away:
- Add to kernel/celltypes.h (incl. eval() handling for non-mem cells)
- Add to InternalCellChecker::check() in kernel/rtlil.cc
- Add to techlibs/common/simlib.v
- Add to techlibs/common/techmap.v
Things to do after finalizing the cell interface:
- Add support to kernel/satgen.h for the new cell type
- Add to docs/source/CHAPTER_CellLib.rst (or just add a fixme to the bottom)
- Maybe add support to the Verilog backend for dumping such cells as expression
Checklist for creating Yosys releases
=====================================
Update the CHANGELOG file:
cd ~yosys
gitk &
vi CHANGELOG
Update and check documentation:
cd ~yosys
make docs
- sanity check the figures in docs/images
- if there are any odd things -> investigate
cd ~yosys
vi README guidelines/*
- is the information provided in those file still up to date
Then with default config setting:
cd ~yosys
make vgtest
cd ~yosys
./yosys -p 'proc; show' tests/simple/fiedler-cooley.v
./yosys -p 'proc; opt; show' tests/simple/fiedler-cooley.v
./yosys -p 'synth; show' tests/simple/fiedler-cooley.v
./yosys -p 'synth_xilinx -top up3down5; show' tests/simple/fiedler-cooley.v
cd ~yosys/examples/cmos
bash testbench.sh
cd ~yosys/examples/basys3
bash run.sh
Test building plugins with various of the standard passes:
yosys-config --build test.so equiv_simple.cc
- also check the code examples in guidelines/GettingStarted
And if a version of the verific library is currently available:
cd ~yosys
cat frontends/verific/build_amd64.txt
- follow instructions
cd frontends/verific
../../yosys test_navre.ys
Finally run all tests with "make config-{clang,gcc}":
cd ~yosys
make clean
make test
make ystests
make vloghtb
make install
cd ~yosys-bigsim
make clean
make full
cd ~vloghammer
make purge gen_issues gen_samples
make SYN_LIST="yosys" SIM_LIST="icarus yosim verilator" REPORT_FULL=1 world
chromium-browser report.html
Release:
- set YOSYS_VER to x.y.z in Makefile
- remove "bumpversion" target from Makefile
- update version string in CHANGELOG
git commit -am "Yosys x.y.z"
- push tag to github
- post changelog on github
- post short release note on reddit
Updating the website:
cd ~yosys
make install
cd ~yosys-web
make update_show
git commit -am update
make push
- Read the Docs updates handled by Jenkins on source change

72
guidelines/CodeOfConduct
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@ -1,72 +0,0 @@
Contributor Covenant Code of Conduct
Our Pledge
In the interest of fostering an open and welcoming environment, we as
contributors and maintainers pledge to making participation in our project and
our community a harassment-free experience for everyone, regardless of age, body
size, disability, ethnicity, gender identity and expression, level of experience,
nationality, personal appearance, race, religion, or sexual identity and
orientation.
Our Standards
Examples of behavior that contributes to creating a positive environment
include:
* Using welcoming and inclusive language
* Being respectful of differing viewpoints and experiences
* Gracefully accepting constructive criticism
* Focusing on what is best for the community
* Showing empathy towards other community members
Examples of unacceptable behavior by participants include:
* The use of sexualized language or imagery and unwelcome sexual attention or
advances
* Trolling, insulting/derogatory comments, and personal or political attacks
* Public or private harassment
* Publishing others' private information, such as a physical or electronic
address, without explicit permission
* Other conduct which could reasonably be considered inappropriate in a
professional setting
Our Responsibilities
Project maintainers are responsible for clarifying the standards of acceptable
behavior and are expected to take appropriate and fair corrective action in
response to any instances of unacceptable behavior.
Project maintainers have the right and responsibility to remove, edit, or
reject comments, commits, code, wiki edits, issues, and other contributions
that are not aligned to this Code of Conduct, or to ban temporarily or
permanently any contributor for other behaviors that they deem inappropriate,
threatening, offensive, or harmful.
Scope
This Code of Conduct applies both within project spaces and in public spaces
when an individual is representing the project or its community. Examples of
representing a project or community include using an official project e-mail
address, posting via an official social media account, or acting as an appointed
representative at an online or offline event. Representation of a project may be
further defined and clarified by project maintainers.
Enforcement
Instances of abusive, harassing, or otherwise unacceptable behavior may be
reported by contacting the project team at contact@yosyshq.com and/or
claire@clairexen.net. All complaints will be reviewed and investigated and
will result in a response that is deemed necessary and appropriate to the
circumstances. The project team is obligated to maintain confidentiality with
regard to the reporter of an incident. Further details of specific enforcement
policies may be posted separately.
Project maintainers who do not follow or enforce the Code of Conduct in good
faith may face temporary or permanent repercussions as determined by other
members of the project's leadership.
Attribution
This Code of Conduct is adapted from the Contributor Covenant, version 1.4,
available at http://contributor-covenant.org/version/1/4/

34
guidelines/CodingStyle
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@ -1,34 +0,0 @@
Coding Style
============
Formatting of code
------------------
- Yosys code is using tabs for indentation. Tabs are 8 characters.
- A continuation of a statement in the following line is indented by
two additional tabs.
- Lines are as long as you want them to be. A good rule of thumb is
to break lines at about column 150.
- Opening braces can be put on the same or next line as the statement
opening the block (if, switch, for, while, do). Put the opening brace
on its own line for larger blocks, especially blocks that contains
blank lines.
- Otherwise stick to the Linux Kernel Coding Style:
https://www.kernel.org/doc/Documentation/process/coding-style.rst
C++ Language
-------------
Yosys is written in C++17.
In general Yosys uses "int" instead of "size_t". To avoid compiler
warnings for implicit type casts, always use "GetSize(foobar)" instead
of "foobar.size()". (GetSize() is defined in kernel/yosys.h)
Use range-based for loops whenever applicable.

69
guidelines/UnitTests
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@ -1,69 +0,0 @@
How to add unit test
====================
Unit test brings some advantages, briefly, we can list some of them (reference
[1](https://en.wikipedia.org/wiki/Unit_testing)):
* Tests reduce bugs in new features;
* Tests reduce bugs in existing features;
* Tests are good documentation;
* Tests reduce the cost of change;
* Tests allow refactoring;
With those advantages in mind, it was required to choose a framework which fits
well with C/C++ code. Hence, it was chosen (google test)
[https://github.com/google/googletest], because it is largely used and it is
relatively easy learn.
Install and configure google test (manually)
--------------------------------------------
In this section, you will see a brief description of how to install google
test. However, it is strongly recommended that you take a look to the official
repository (https://github.com/google/googletest) and refers to that if you
have any problem to install it. Follow the steps below:
* Install: cmake and pthread
* Clone google test project from: https://github.com/google/googletest and
enter in the project directory
* Inside project directory, type:
```
cmake -DBUILD_SHARED_LIBS=ON .
make
```
* After compilation, copy all "*.so" inside directory "googlemock" and
"googlemock/gtest" to "/usr/lib/"
* Done! Now you can compile your tests.
If you have any problem, go to the official repository to find help.
Ps.: Some distros already have googletest packed. If your distro supports it,
you can use it instead of compile.
Create new unit test
--------------------
If you want to add new unit tests for Yosys, just follow the steps below:
* Go to directory "yosys/test/unit/"
* In this directory you can find something similar Yosys's directory structure.
To create your unit test file you have to follow this pattern:
fileNameToImplementUnitTest + Test.cc. E.g.: if you want to implement the
unit test for kernel/celledges.cc, you will need to create a file like this:
tests/unit/kernel/celledgesTest.cc;
* Implement your unit test
Run unit test
-------------
To compile and run all unit tests, just go to yosys root directory and type:
```
make unit-test
```
If you want to remove all unit test files, type:
```
make clean-unit-test
```

83
guidelines/Windows
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Creating the Visual Studio Template Project
===========================================
1. Create an empty Visual C++ Win32 Console App project
Microsoft Visual Studio Express 2013 for Windows Desktop
Open New Project Wizard (File -> New Project..)
Project Name: YosysVS
Solution Name: YosysVS
[X] Create directory for solution
[ ] Add to source control
[X] Console applications
[X] Empty Project
[ ] SDL checks
2. Open YosysVS Project Properties
Select Configuration: All Configurations
C/C++ -> General -> Additional Include Directories
Add: ..\yosys
C/C++ -> Preprocessor -> Preprocessor Definitions
Add: _YOSYS_;_CRT_SECURE_NO_WARNINGS
3. Resulting file system tree:
YosysVS/
YosysVS/YosysVS
YosysVS/YosysVS/YosysVS.vcxproj
YosysVS/YosysVS/YosysVS.vcxproj.filters
YosysVS/YosysVS.sdf
YosysVS/YosysVS.sln
YosysVS/YosysVS.v12.suo
4. Zip YosysVS as YosysVS-Tpl-v1.zip
Compiling with Visual Studio
============================
Visual Studio builds are not directly supported by build scripts, but they are still possible.
1. Easy way
- Go to https://github.com/YosysHQ/yosys/actions/workflows/vs.yml?query=branch%3Amain
- Click on the most recent completed run
- In Artifacts region find vcxsrc and click on it to download
- Unpack downloaded ZIP file
- Open YosysVS.sln with Visual Studio
2. Using WSL or MSYS2
- Make sure to have make, python3 and git available
- Git clone yosys repository
- Execute ```make vcxsrc YOSYS_VER=latest```
- File yosys-win32-vcxsrc-latest.zip will be created
- Transfer that file to location visible by Windows application
- Unpack ZIP
- Open YosysVS.sln with Visual Studio
Cross-Building for Windows with MXE
===================================
Check http://mxe.cc/#requirements and install all missing requirements.
As root (or other user with write access to /usr/local/src):
cd /usr/local/src
git clone https://github.com/mxe/mxe.git
cd mxe
make -j$(nproc) MXE_PLUGIN_DIRS="plugins/tcl.tk" \
MXE_TARGETS="i686-w64-mingw32.static" \
gcc tcl readline
Then as regular user in some directory where you build stuff:
git clone https://github.com/YosysHQ/yosys.git yosys-win32
cd yosys-win32
make config-mxe
make -j$(nproc) mxebin

15
kernel/rtlil.cc
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@ -2147,6 +2147,21 @@ namespace {
check_expected();
return;
}
/*
* Checklist for adding internal cell types
* ========================================
* Things to do right away:
* - Add to kernel/celltypes.h (incl. eval() handling for non-mem cells)
* - Add to InternalCellChecker::check() in kernel/rtlil.cc
* - Add to techlibs/common/simlib.v
* - Add to techlibs/common/techmap.v
*
* Things to do after finalizing the cell interface:
* - Add support to kernel/satgen.h for the new cell type
* - Add to docs/source/CHAPTER_CellLib.rst (or just add a fixme to the bottom)
* - Maybe add support to the Verilog backend for dumping such cells as expression
*
*/
error(__LINE__);
}
};

2
kernel/yosys.h
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@ -32,8 +32,6 @@
//
// This header is very boring. It just defines some general things that
// belong nowhere else and includes the interesting headers.
//
// Find more information in the "guidelines/GettingStarted" file.
#ifndef YOSYS_H