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Goodbye guidelines (except GettingStarted) 

Drop the parts that are being dropped.
Move the things that are being moved.
Also move the verilog stuff out of README and into the docs.
GettingStarted is less cut and dry, so hold off on that one.
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@ -273,371 +273,6 @@ source with another tool such as
``verilator --lint-only``. ``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 Building the documentation
========================== ==========================
@ -673,3 +308,68 @@ From the root of the repository, run `make docs`. This will build/rebuild yosys
as necessary before generating the website documentation from the yosys help as necessary before generating the website documentation from the yosys help
commands. To build for pdf instead of html, call commands. To build for pdf instead of html, call
`make docs DOC_TARGET=latexpdf`. `make docs DOC_TARGET=latexpdf`.
Building for Windows
====================
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

12
guidelines/CodingStyle → docs/source/yosys_internals/extending_yosys/contributing.rst
View File

@ -1,9 +1,11 @@
Coding Style Contributing to Yosys
============ =====================
Coding Style
------------
Formatting of code Formatting of code
------------------ ~~~~~~~~~~~~~~~~~~
- Yosys code is using tabs for indentation. Tabs are 8 characters. - Yosys code is using tabs for indentation. Tabs are 8 characters.
@ -23,7 +25,7 @@ Formatting of code
C++ Language C++ Language
------------- ~~~~~~~~~~~~
Yosys is written in C++17. Yosys is written in C++17.
@ -31,4 +33,4 @@ In general Yosys uses "int" instead of "size_t". To avoid compiler
warnings for implicit type casts, always use "GetSize(foobar)" instead warnings for implicit type casts, always use "GetSize(foobar)" instead
of "foobar.size()". (GetSize() is defined in kernel/yosys.h) of "foobar.size()". (GetSize() is defined in kernel/yosys.h)
Use range-based for loops whenever applicable. Use range-based for loops whenever applicable.

1
docs/source/yosys_internals/extending_yosys/index.rst
View File

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

75
docs/source/yosys_internals/extending_yosys/test_suites.rst
View File

@ -1,7 +1,7 @@
Testing Yosys Testing Yosys
============= =============
.. todo:: more about the included test suite .. TODO:: more about the included test suite and how to add tests
Automatic testing Automatic testing
----------------- -----------------
@ -23,3 +23,76 @@ For up to date information, including OS versions, refer to `the git actions
page`_. page`_.
.. _the git actions page: https://github.com/YosysHQ/yosys/actions .. _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, 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 a 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 tests
~~~~~~~~~~~~~~
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
```

1
docs/source/yosys_internals/index.rst
View File

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

369
docs/source/yosys_internals/verilog.rst Normal file
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@ -0,0 +1,369 @@
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 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.

116
guidelines/Checklists
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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/

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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@ -1,83 +0,0 @@
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
View File

@ -2147,6 +2147,21 @@ namespace {
check_expected(); check_expected();
return; 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__); error(__LINE__);
} }
}; };