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@@ -1,7 +1,7 @@ ``` yosys -- Yosys Open SYnthesis Suite -Copyright (C) 2012 - 2016 Clifford Wolf <clifford@clifford.at> +Copyright (C) 2012 - 2019 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 @@ -34,11 +34,24 @@ compatible license that is similar in terms to the MIT license or the 2-clause BSD license). -Web Site -======== +Web Site and Other Resources +============================ More information and documentation can be found on the Yosys web site: -http://www.clifford.at/yosys/ +- http://www.clifford.at/yosys/ + +The "Documentation" page on the web site contains links to more resources, +including a manual that even describes some of the Yosys internals: +- http://www.clifford.at/yosys/documentation.html + +The file `CodingReadme` in this directory 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 + Setup ====== @@ -52,14 +65,30 @@ 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 mercurial \ - graphviz xdot pkg-config python3 + libreadline-dev gawk tcl-dev libffi-dev git \ + graphviz xdot pkg-config python3 libboost-system-dev \ + libboost-python-dev libboost-filesystem-dev zlib1g-dev -Similarily, on Mac OS X MacPorts or Homebrew can be used to install dependencies: +Similarily, on Mac OS X Homebrew can be used to install dependencies: $ brew tap Homebrew/bundle && brew bundle + +or MacPorts: + $ sudo port install bison flex readline gawk libffi \ - git mercurial graphviz pkgconfig python36 + 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 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 @@ -80,12 +109,15 @@ Makefile. 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). +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 + Getting Started =============== @@ -101,18 +133,15 @@ commands and ``help <command>`` to print details on the specified command: yosys> help help -reading the design using the Verilog frontend: +reading and elaborating the design using the Verilog frontend: - yosys> read_verilog tests/simple/fiedler-cooley.v + yosys> read -sv tests/simple/fiedler-cooley.v + yosys> hierarchy -top up3down5 -writing the design to the console in yosys's internal format: +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: @@ -134,51 +163,26 @@ 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 + read -sv tests/simple/fiedler-cooley.v + hierarchy -top up3down5 + 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: + # read design + read -sv tests/simple/fiedler-cooley.v + hierarchy -top up3down5 + # the high-level stuff - hierarchy; proc; fsm; opt; memory; opt + proc; fsm; opt; memory; opt # mapping to internal cell library techmap; opt @@ -193,7 +197,8 @@ synthesize for the given cell library: 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. +you can use the file ``examples/cmos/cmos_cells.lib`` from the yosys sources +as simple example. Liberty file downloads for and information about free and open ASIC standard cell libraries can be found here: @@ -202,39 +207,33 @@ cell libraries can be found here: - 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: +``help synth``): - # the high-level stuff - hierarchy - synth -run coarse + read -sv tests/simple/fiedler-cooley.v + synth -top up3down5 - # mapping to internal cells - techmap; opt -fast + # mapping to target cells dfflibmap -liberty mycells.lib abc -liberty mycells.lib clean -Yosys is under construction. A more detailed documentation will follow. +The command ``prep`` provides a good default word-level synthesis script, as +used in SMT-based formal verification. Unsupported Verilog-2005 Features ================================= The following Verilog-2005 features are not supported by -yosys and there are currently no plans to add support +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 ``tri``, ``triand`` and ``trior`` net types -- The ``disable``, ``primitive`` and ``specify`` statements - -- Latched logic (is synthesized as logic with feedback loops) +- The ``config`` and ``disable`` keywords and library map files Verilog Attributes and non-standard features @@ -273,16 +272,34 @@ Verilog Attributes and non-standard features 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. + by Yosys to synthesize Verilog functions and access arrays. -- The ``onehot`` attribute on wires mark them as onehot state register. This +- 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. + 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. - 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 @@ -307,13 +324,76 @@ Verilog Attributes and non-standard features through the synthesis. When entities are combined, a new |-separated string is created that contains all the string from the original entities. -- In addition to the ``(* ... *)`` attribute syntax, yosys supports +- 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_box_id`` specifies a positive integer linking a + blackbox or whitebox definition to a corresponding entry in a `abc9` + box-file. + +- 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 port attribute ``abc9_arrival`` specifies an integer (for output ports + only) to be used as the arrival time of this sequential port. It can be used, + for example, to specify the clk-to-Q delay of a flip-flop for consideration + during `abc9` techmapping. + +- 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``. + +- 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 + 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 @@ -323,7 +403,7 @@ Verilog Attributes and non-standard features - When defining a macro with `define, all text between triple double quotes is interpreted as macro body, even if it contains unescaped newlines. The - tipple double quotes are removed from the macro body. For example: + triple double quotes are removed from the macro body. For example: `define MY_MACRO(a, b) """ assign a = 23; @@ -370,37 +450,55 @@ Verilog Attributes and non-standard features $ 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 + 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 ``$finish`` and ``$display`` are supported in initial blocks - in an unconditional context (only if/case statements on parameters - and constant values). The intended use for this is synthesis-time DRC. +- 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.) Non-standard or SystemVerilog features for formal verification ============================================================== -- Support for ``assert``, ``assume``, ``restrict``, and ``cover'' is enabled +- Support for ``assert``, ``assume``, ``restrict``, and ``cover`` is enabled when ``read_verilog`` is called with ``-formal``. - The system task ``$initstate`` evaluates to 1 in the initial state and to 0 otherwise. -- The system task ``$anyconst`` evaluates to any constant value. This is +- The system function ``$anyconst`` evaluates to any constant value. This is equivalent to declaring a reg as ``rand const``, but also works outside of checkers. (Yosys also supports ``rand const`` outside checkers.) -- The system task ``$anyseq`` evaluates to any value, possibly a different +- 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 ($ff cells). + explicit clock input (``$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 @@ -411,7 +509,7 @@ 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 a $assert cell. + always block: ``assert(<expression>);``. It is transformed to an ``$assert`` cell. - The ``assume``, ``restrict``, and ``cover`` statements from SystemVerilog are also supported. The same limitations as with the ``assert`` statement apply. @@ -428,6 +526,11 @@ from SystemVerilog: 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) + +- SystemVerilog interfaces (SVIs) are supported. Modports for specifying whether + ports are inputs or outputs are supported. + Building the documentation ========================== @@ -458,6 +561,6 @@ Then execute, from the root of the repository: Notes: -- To run `make manual` you need to have installed yosys with `make install`, +- To run `make manual` you need to have installed Yosys with `make install`, otherwise it will fail on finding `kernel/yosys.h` while building `PRESENTATION_Prog`. |