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|
```
yosys -- Yosys Open SYnthesis Suite
Copyright (C) 2012 - 2018 Clifford Wolf <clifford@clifford.at>
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
===================================
This is a framework for RTL synthesis tools. It currently has
extensive Verilog-2005 support and provides a basic set of
synthesis algorithms for various application domains.
Yosys can be adapted to perform any synthesis job by combining
the existing passes (algorithms) using synthesis scripts and
adding additional passes as needed by extending the yosys C++
code base.
Yosys is free software licensed under the ISC license (a GPL
compatible license that is similar in terms to the MIT license
or the 2-clause BSD license).
Web Site
========
More information and documentation can be found on the Yosys web site:
http://www.clifford.at/yosys/
Setup
======
You need a C++ compiler with C++11 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).
Xdot (graphviz) is used by the ``show`` command in yosys to display schematics.
For example on Ubuntu Linux 16.04 LTS the following commands will install all
prerequisites for building yosys:
$ sudo apt-get install build-essential clang bison flex \
libreadline-dev gawk tcl-dev libffi-dev git \
graphviz xdot pkg-config python3
Similarily, on Mac OS X MacPorts or Homebrew can be used to install dependencies:
$ brew tap Homebrew/bundle && brew bundle
$ sudo port install bison flex readline gawk libffi \
git graphviz pkgconfig python36
On FreeBSD use the following command to install all prerequisites:
# pkg install bison flex readline gawk libffi\
git graphviz pkgconfig python3 python36 tcl-wrapper
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
There are also pre-compiled Yosys binary packages for Ubuntu and Win32 as well
as a source distribution for Visual Studio. Visit the Yosys download page for
more information: http://www.clifford.at/yosys/download.html
To configure the build system to use a specific compiler, use one of
$ make config-clang
$ make config-gcc
For other compilers and build configurations it might be
necessary to make some changes to the config section of the
Makefile.
$ vi Makefile # ..or..
$ vi Makefile.conf
To build Yosys simply type 'make' in this directory.
$ make
$ make test
$ sudo make install
Note that this also downloads, builds and installs ABC (using yosys-abc
as executable name).
Getting Started
===============
Yosys can be used with the interactive command shell, with
synthesis scripts or with command line arguments. Let's perform
a simple synthesis job using the interactive command shell:
$ ./yosys
yosys>
the command ``help`` can be used to print a list of all available
commands and ``help <command>`` to print details on the specified command:
yosys> help help
reading the design using the Verilog frontend:
yosys> read_verilog tests/simple/fiedler-cooley.v
writing the design to the console in Yosys's internal format:
yosys> write_ilang
elaborate design hierarchy:
yosys> hierarchy
convert processes (``always`` blocks) to netlist elements and perform
some simple optimizations:
yosys> proc; opt
display design netlist using ``xdot``:
yosys> show
the same thing using ``gv`` as postscript viewer:
yosys> show -format ps -viewer gv
translating netlist to gate logic and perform some simple optimizations:
yosys> techmap; opt
write design netlist to a new Verilog file:
yosys> write_verilog synth.v
a similar synthesis can be performed using yosys command line options only:
$ ./yosys -o synth.v -p hierarchy -p proc -p opt \
-p techmap -p opt tests/simple/fiedler-cooley.v
or using a simple synthesis script:
$ cat synth.ys
read_verilog tests/simple/fiedler-cooley.v
hierarchy; proc; opt; techmap; opt
write_verilog synth.v
$ ./yosys synth.ys
It is also possible to only have the synthesis commands but not the read/write
commands in the synthesis script:
$ cat synth.ys
hierarchy; proc; opt; techmap; opt
$ ./yosys -o synth.v tests/simple/fiedler-cooley.v synth.ys
The following very basic synthesis script should work well with all designs:
# check design hierarchy
hierarchy
# translate processes (always blocks)
proc; opt
# detect and optimize FSM encodings
fsm; opt
# implement memories (arrays)
memory; opt
# convert to gate logic
techmap; opt
If ABC is enabled in the Yosys build configuration and a cell library is given
in the liberty file ``mycells.lib``, the following synthesis script will
synthesize for the given cell library:
# the high-level stuff
hierarchy; proc; fsm; opt; memory; opt
# mapping to internal cell library
techmap; opt
# mapping flip-flops to mycells.lib
dfflibmap -liberty mycells.lib
# mapping logic to mycells.lib
abc -liberty mycells.lib
# cleanup
clean
If you do not have a liberty file but want to test this synthesis script,
you can use the file ``examples/cmos/cmos_cells.lib`` from the yosys sources.
Liberty file downloads for and information about free and open ASIC standard
cell libraries can be found here:
- http://www.vlsitechnology.org/html/libraries.html
- http://www.vlsitechnology.org/synopsys/vsclib013.lib
The command ``synth`` provides a good default synthesis script (see
``help synth``). If possible a synthesis script should borrow from ``synth``.
For example:
# the high-level stuff
hierarchy
synth -run coarse
# mapping to internal cells
techmap; opt -fast
dfflibmap -liberty mycells.lib
abc -liberty mycells.lib
clean
Yosys is under construction. A more detailed documentation will follow.
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``, ``trior``, ``wand`` and ``wor`` net types
- The ``config`` keyword and library map files
- The ``disable``, ``primitive`` and ``specify`` statements
- Latched logic (is synthesized as logic with feedback loops)
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 ``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.
|