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Move (most of) ExOth and ExAdv slides
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Krystine Sherwin
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271
docs/source/yosys_internals/flow/command_ordering.rst
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271
docs/source/yosys_internals/flow/command_ordering.rst
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Command ordering
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----------------
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.. TODO: copypaste
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Intro to coarse-grain synthesis
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~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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In coarse-grain synthesis the target architecture has cells of the same
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complexity or larger complexity than the internal RTL representation.
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For example:
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.. code:: verilog
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wire [15:0] a, b;
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wire [31:0] c, y;
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assign y = a * b + c;
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This circuit contains two cells in the RTL representation: one multiplier and
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one adder. In some architectures this circuit can be implemented using
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a single circuit element, for example an FPGA DSP core. Coarse grain synthesis
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is this mapping of groups of circuit elements to larger components.
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Fine-grain synthesis would be matching the circuit elements to smaller
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components, such as LUTs, gates, or half- and full-adders.
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The extract pass
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~~~~~~~~~~~~~~~~
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- Like the ``techmap`` pass, the ``extract`` pass is called with a map file. It
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compares the circuits inside the modules of the map file with the design and
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looks for sub-circuits in the design that match any of the modules in the map
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file.
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- If a match is found, the ``extract`` pass will replace the matching subcircuit
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with an instance of the module from the map file.
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- In a way the ``extract`` pass is the inverse of the techmap pass.
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.. TODO: copypaste
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.. figure:: ../../../images/res/PRESENTATION_ExAdv/macc_simple_test_00a.*
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:class: width-helper
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before `extract`
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.. figure:: ../../../images/res/PRESENTATION_ExAdv/macc_simple_test_00b.*
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:class: width-helper
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after `extract`
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.. literalinclude:: ../../../resources/PRESENTATION_ExAdv/macc_simple_test.v
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:language: verilog
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:caption: ``docs/resources/PRESENTATION_ExAdv/macc_simple_test.v``
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.. literalinclude:: ../../../resources/PRESENTATION_ExAdv/macc_simple_xmap.v
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:language: verilog
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:caption: ``docs/resources/PRESENTATION_ExAdv/macc_simple_xmap.v``
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.. code:: yoscrypt
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read_verilog macc_simple_test.v
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hierarchy -check -top test
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extract -map macc_simple_xmap.v;;
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.. literalinclude:: ../../../resources/PRESENTATION_ExAdv/macc_simple_test_01.v
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:language: verilog
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:caption: ``docs/resources/PRESENTATION_ExAdv/macc_simple_test_01.v``
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.. figure:: ../../../images/res/PRESENTATION_ExAdv/macc_simple_test_01a.*
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:class: width-helper
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.. figure:: ../../../images/res/PRESENTATION_ExAdv/macc_simple_test_01b.*
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:class: width-helper
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.. literalinclude:: ../../../resources/PRESENTATION_ExAdv/macc_simple_test_02.v
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:language: verilog
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:caption: ``docs/resources/PRESENTATION_ExAdv/macc_simple_test_02.v``
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.. figure:: ../../../images/res/PRESENTATION_ExAdv/macc_simple_test_02a.*
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:class: width-helper
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.. figure:: ../../../images/res/PRESENTATION_ExAdv/macc_simple_test_02b.*
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:class: width-helper
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The wrap-extract-unwrap method
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~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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Often a coarse-grain element has a constant bit-width, but can be used to
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implement operations with a smaller bit-width. For example, a 18x25-bit multiplier
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can also be used to implement 16x20-bit multiplication.
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A way of mapping such elements in coarse grain synthesis is the wrap-extract-unwrap method:
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wrap
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Identify candidate-cells in the circuit and wrap them in a cell with a constant
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wider bit-width using ``techmap``. The wrappers use the same parameters as the original cell, so
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the information about the original width of the ports is preserved.
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Then use the ``connwrappers`` command to connect up the bit-extended in- and
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outputs of the wrapper cells.
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extract
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Now all operations are encoded using the same bit-width as the coarse grain
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element. The ``extract`` command can be used to replace circuits with cells
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of the target architecture.
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unwrap
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The remaining wrapper cell can be unwrapped using ``techmap``.
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Example: DSP48_MACC
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~~~~~~~~~~~~~~~~~~~
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This section details an example that shows how to map MACC operations of
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arbitrary size to MACC cells with a 18x25-bit multiplier and a 48-bit adder
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(such as the Xilinx DSP48 cells).
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Preconditioning: ``macc_xilinx_swap_map.v``
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Make sure ``A`` is the smaller port on all multipliers
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.. TODO: copypaste
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.. literalinclude:: ../../../resources/PRESENTATION_ExAdv/macc_xilinx_swap_map.v
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:language: verilog
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:caption: ``docs/resources/PRESENTATION_ExAdv/macc_xilinx_swap_map.v``
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Wrapping multipliers: ``macc_xilinx_wrap_map.v``
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.. literalinclude:: ../../../resources/PRESENTATION_ExAdv/macc_xilinx_wrap_map.v
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:language: verilog
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:lines: 1-46
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:caption: ``docs/resources/PRESENTATION_ExAdv/macc_xilinx_wrap_map.v``
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Wrapping adders: ``macc_xilinx_wrap_map.v``
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.. literalinclude:: ../../../resources/PRESENTATION_ExAdv/macc_xilinx_wrap_map.v
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:language: verilog
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:lines: 48-89
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:caption: ``docs/resources/PRESENTATION_ExAdv/macc_xilinx_wrap_map.v``
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Extract: ``macc_xilinx_xmap.v``
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.. literalinclude:: ../../../resources/PRESENTATION_ExAdv/macc_xilinx_xmap.v
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:language: verilog
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:caption: ``docs/resources/PRESENTATION_ExAdv/macc_xilinx_xmap.v``
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... simply use the same wrapping commands on this module as on the design to create a template for the ``extract`` command.
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Unwrapping multipliers: ``macc_xilinx_unwrap_map.v``
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.. literalinclude:: ../../../resources/PRESENTATION_ExAdv/macc_xilinx_unwrap_map.v
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:language: verilog
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:lines: 1-30
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:caption: ``docs/resources/PRESENTATION_ExAdv/macc_xilinx_unwrap_map.v``
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Unwrapping adders: ``macc_xilinx_unwrap_map.v``
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.. literalinclude:: ../../../resources/PRESENTATION_ExAdv/macc_xilinx_unwrap_map.v
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:language: verilog
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:lines: 32-61
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:caption: ``docs/resources/PRESENTATION_ExAdv/macc_xilinx_unwrap_map.v``
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.. literalinclude:: ../../../resources/PRESENTATION_ExAdv/macc_xilinx_test.v
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:language: verilog
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:lines: 1-6
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:caption: ``test1`` of ``docs/resources/PRESENTATION_ExAdv/macc_xilinx_test.v``
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.. figure:: ../../../images/res/PRESENTATION_ExAdv/macc_xilinx_test1a.*
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:class: width-helper
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.. figure:: ../../../images/res/PRESENTATION_ExAdv/macc_xilinx_test1b.*
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:class: width-helper
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.. literalinclude:: ../../../resources/PRESENTATION_ExAdv/macc_xilinx_test.v
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:language: verilog
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:lines: 8-13
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:caption: ``test2`` of ``docs/resources/PRESENTATION_ExAdv/macc_xilinx_test.v``
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.. figure:: ../../../images/res/PRESENTATION_ExAdv/macc_xilinx_test2a.*
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:class: width-helper
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.. figure:: ../../../images/res/PRESENTATION_ExAdv/macc_xilinx_test2b.*
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:class: width-helper
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Wrapping in ``test1``:
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.. figure:: ../../../images/res/PRESENTATION_ExAdv/macc_xilinx_test1b.*
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:class: width-helper
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.. code:: yoscrypt
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techmap -map macc_xilinx_wrap_map.v
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connwrappers -unsigned $__mul_wrapper \
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Y Y_WIDTH \
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-unsigned $__add_wrapper \
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Y Y_WIDTH ;;
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.. figure:: ../../../images/res/PRESENTATION_ExAdv/macc_xilinx_test1c.*
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:class: width-helper
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Wrapping in ``test2``:
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.. figure:: ../../../images/res/PRESENTATION_ExAdv/macc_xilinx_test2b.*
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:class: width-helper
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.. code:: yoscrypt
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techmap -map macc_xilinx_wrap_map.v
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connwrappers -unsigned $__mul_wrapper \
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Y Y_WIDTH \
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-unsigned $__add_wrapper \
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Y Y_WIDTH ;;
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.. figure:: ../../../images/res/PRESENTATION_ExAdv/macc_xilinx_test2c.*
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:class: width-helper
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Extract in ``test1``:
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.. code:: yoscrypt
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design -push
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read_verilog macc_xilinx_xmap.v
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techmap -map macc_xilinx_swap_map.v
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techmap -map macc_xilinx_wrap_map.v;;
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design -save __macc_xilinx_xmap
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design -pop
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extract -constports -ignore_parameters \
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-map %__macc_xilinx_xmap \
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-swap $__add_wrapper A,B ;;
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.. figure:: ../../../images/res/PRESENTATION_ExAdv/macc_xilinx_test1c.*
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:class: width-helper
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.. figure:: ../../../images/res/PRESENTATION_ExAdv/macc_xilinx_test1d.*
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:class: width-helper
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Extract in ``test2``:
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.. code:: yoscrypt
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design -push
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read_verilog macc_xilinx_xmap.v
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techmap -map macc_xilinx_swap_map.v
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techmap -map macc_xilinx_wrap_map.v;;
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design -save __macc_xilinx_xmap
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design -pop
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extract -constports -ignore_parameters \
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-map %__macc_xilinx_xmap \
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-swap $__add_wrapper A,B ;;
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.. figure:: ../../../images/res/PRESENTATION_ExAdv/macc_xilinx_test2c.*
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:class: width-helper
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.. figure:: ../../../images/res/PRESENTATION_ExAdv/macc_xilinx_test2d.*
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:class: width-helper
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Unwrap in ``test2``:
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.. figure:: ../../../images/res/PRESENTATION_ExAdv/macc_xilinx_test2d.*
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:class: width-helper
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.. figure:: ../../../images/res/PRESENTATION_ExAdv/macc_xilinx_test2e.*
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:class: width-helper
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.. code:: yoscrypt
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techmap -map macc_xilinx_unwrap_map.v ;;
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@ -17,4 +17,6 @@ This scripts contain three types of commands:
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overview
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control_and_data
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verilog_frontend
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command_ordering
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model_checking
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106
docs/source/yosys_internals/flow/model_checking.rst
Normal file
106
docs/source/yosys_internals/flow/model_checking.rst
Normal file
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@ -0,0 +1,106 @@
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Symbolic model checking
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-----------------------
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.. TODO: copypaste
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.. note::
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While it is possible to perform model checking directly in Yosys, it
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is highly recommended to use SBY or EQY for formal hardware verification.
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Symbolic Model Checking (SMC) is used to formally prove that a circuit has (or
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has not) a given property.
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One application is Formal Equivalence Checking: Proving that two circuits are
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identical. For example this is a very useful feature when debugging custom
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passes in Yosys.
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Other applications include checking if a module conforms to interface standards.
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The ``sat`` command in Yosys can be used to perform Symbolic Model Checking.
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Checking techmap
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~~~~~~~~~~~~~~~~
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Remember the following example from :doc:`/getting_started/typical_phases`?
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.. literalinclude:: ../../../resources/PRESENTATION_ExSyn/techmap_01_map.v
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:language: verilog
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:caption: ``docs/resources/PRESENTATION_ExSyn/techmap_01_map.v``
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.. literalinclude:: ../../../resources/PRESENTATION_ExSyn/techmap_01.v
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:language: verilog
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:caption: ``docs/resources/PRESENTATION_ExSyn/techmap_01.v``
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.. literalinclude:: ../../../resources/PRESENTATION_ExSyn/techmap_01.ys
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:language: yoscrypt
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:caption: ``docs/resources/PRESENTATION_ExSyn/techmap_01.ys``
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Lets see if it is correct..
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.. code:: yoscrypt
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# read test design
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read_verilog techmap_01.v
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hierarchy -top test
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# create two version of the design: test_orig and test_mapped
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copy test test_orig
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rename test test_mapped
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# apply the techmap only to test_mapped
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techmap -map techmap_01_map.v test_mapped
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# create a miter circuit to test equivalence
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miter -equiv -make_assert -make_outputs test_orig test_mapped miter
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flatten miter
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# run equivalence check
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sat -verify -prove-asserts -show-inputs -show-outputs miter
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Result:
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.. code::
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Solving problem with 945 variables and 2505 clauses..
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SAT proof finished - no model found: SUCCESS!
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AXI4 Stream Master
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~~~~~~~~~~~~~~~~~~
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The following AXI4 Stream Master has a bug. But the bug is not exposed if the
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slave keeps ``tready`` asserted all the time. (Something a test bench might do.)
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Symbolic Model Checking can be used to expose the bug and find a sequence of
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values for ``tready`` that yield the incorrect behavior.
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.. literalinclude:: ../../../resources/PRESENTATION_ExOth/axis_master.v
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:language: verilog
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:caption: ``docs/resources/PRESENTATION_ExOth/axis_master.v``
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.. literalinclude:: ../../../resources/PRESENTATION_ExOth/axis_test.v
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:language: verilog
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:caption: ``docs/resources/PRESENTATION_ExOth/axis_test.v``
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.. code:: yoscrypt
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read_verilog -sv axis_master.v axis_test.v
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hierarchy -top axis_test
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proc; flatten;;
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sat -seq 50 -prove-asserts
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Result with unmodified ``axis_master.v``:
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.. code::
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Solving problem with 159344 variables and 442126 clauses..
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SAT proof finished - model found: FAIL!
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|
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Result with fixed ``axis_master.v``:
|
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|
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.. code::
|
||||
|
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Solving problem with 159144 variables and 441626 clauses..
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SAT proof finished - no model found: SUCCESS!
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|
|
@ -31,7 +31,7 @@ provided implementation.
|
|||
|
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When no map file is provided, techmap uses a built-in map file that maps the
|
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Yosys RTL cell types to the internal gate library used by Yosys. The curious
|
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reader may find this map file as techlibs/common/techmap.v in the Yosys source
|
||||
reader may find this map file as `techlibs/common/techmap.v` in the Yosys source
|
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tree.
|
||||
|
||||
Additional features have been added to techmap to allow for conditional mapping
|
||||
|
|
@ -105,3 +105,186 @@ reporting bugs in the tools involved. When the information in the Liberty file
|
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used by Yosys and ABC are not part of the sensitive information, the additional
|
||||
tool yosys-filterlib (see :ref:`sec:filterlib`) can be used to strip the
|
||||
sensitive information from the Liberty file.
|
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|
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Techmap by example
|
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------------------
|
||||
|
||||
.. TODO: copypaste
|
||||
|
||||
As a quick recap, the ``techmap`` command replaces cells in the design with
|
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implementations given as Verilog code (called "map files"). It can replace
|
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Yosys' internal cell types (such as ``$or``) as well as user-defined cell
|
||||
types.
|
||||
|
||||
- Verilog parameters are used extensively to customize the internal cell types.
|
||||
- Additional special parameters are used by techmap to communicate meta-data to
|
||||
the map files.
|
||||
- Special wires are used to instruct techmap how to handle a module in the map
|
||||
file.
|
||||
- Generate blocks and recursion are powerful tools for writing map files.
|
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|
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Mapping OR3X1
|
||||
~~~~~~~~~~~~~
|
||||
|
||||
.. note::
|
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|
||||
This is a simple example for demonstration only. Techmap shouldn't be used
|
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to implement basic logic optimization.
|
||||
|
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.. literalinclude:: ../../resources/PRESENTATION_ExAdv/red_or3x1_map.v
|
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:language: verilog
|
||||
:caption: ``docs/resources/PRESENTATION_ExAdv/red_or3x1_map.v``
|
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|
||||
.. figure:: ../../images/res/PRESENTATION_ExAdv/red_or3x1.*
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:class: width-helper
|
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|
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.. literalinclude:: ../../resources/PRESENTATION_ExAdv/red_or3x1_test.ys
|
||||
:language: yoscrypt
|
||||
:caption: ``docs/resources/PRESENTATION_ExAdv/red_or3x1_test.ys``
|
||||
|
||||
.. literalinclude:: ../../resources/PRESENTATION_ExAdv/red_or3x1_test.v
|
||||
:language: verilog
|
||||
:caption: ``docs/resources/PRESENTATION_ExAdv/red_or3x1_test.v``
|
||||
|
||||
Conditional techmap
|
||||
~~~~~~~~~~~~~~~~~~~
|
||||
|
||||
- In some cases only cells with certain properties should be substituted.
|
||||
- The special wire ``_TECHMAP_FAIL_`` can be used to disable a module
|
||||
in the map file for a certain set of parameters.
|
||||
- The wire ``_TECHMAP_FAIL_`` must be set to a constant value. If it
|
||||
is non-zero then the module is disabled for this set of parameters.
|
||||
- Example use-cases:
|
||||
|
||||
- coarse-grain cell types that only operate on certain bit widths
|
||||
- memory resources for different memory geometries (width, depth, ports, etc.)
|
||||
|
||||
Example:
|
||||
|
||||
.. figure:: ../../images/res/PRESENTATION_ExAdv/sym_mul.*
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:class: width-helper
|
||||
|
||||
.. literalinclude:: ../../resources/PRESENTATION_ExAdv/sym_mul_map.v
|
||||
:language: verilog
|
||||
:caption: ``docs/resources/PRESENTATION_ExAdv/sym_mul_map.v``
|
||||
|
||||
.. literalinclude:: ../../resources/PRESENTATION_ExAdv/sym_mul_test.v
|
||||
:language: verilog
|
||||
:caption: ``docs/resources/PRESENTATION_ExAdv/sym_mul_test.v``
|
||||
|
||||
.. literalinclude:: ../../resources/PRESENTATION_ExAdv/sym_mul_test.ys
|
||||
:language: yoscrypt
|
||||
:caption: ``docs/resources/PRESENTATION_ExAdv/sym_mul_test.ys``
|
||||
|
||||
|
||||
Scripting in map modules
|
||||
~~~~~~~~~~~~~~~~~~~~~~~~
|
||||
|
||||
- The special wires ``_TECHMAP_DO_*`` can be used to run Yosys scripts
|
||||
in the context of the replacement module.
|
||||
- The wire that comes first in alphabetical oder is interpreted as string (must
|
||||
be connected to constants) that is executed as script. Then the wire is
|
||||
removed. Repeat.
|
||||
- You can even call techmap recursively!
|
||||
- Example use-cases:
|
||||
|
||||
- Using always blocks in map module: call ``proc``
|
||||
- Perform expensive optimizations (such as ``freduce``) on cells where
|
||||
this is known to work well.
|
||||
- Interacting with custom commands.
|
||||
|
||||
.. note:: PROTIP:
|
||||
Commands such as ``shell``, ``show -pause``, and ``dump`` can be use
|
||||
in the ``_TECHMAP_DO_*`` scripts for debugging map modules.
|
||||
|
||||
Example:
|
||||
|
||||
.. figure:: ../../images/res/PRESENTATION_ExAdv/mymul.*
|
||||
:class: width-helper
|
||||
|
||||
.. literalinclude:: ../../resources/PRESENTATION_ExAdv/mymul_map.v
|
||||
:language: verilog
|
||||
:caption: ``docs/resources/PRESENTATION_ExAdv/mymul_map.v``
|
||||
|
||||
.. literalinclude:: ../../resources/PRESENTATION_ExAdv/mymul_test.v
|
||||
:language: verilog
|
||||
:caption: ``docs/resources/PRESENTATION_ExAdv/mymul_test.v``
|
||||
|
||||
.. literalinclude:: ../../resources/PRESENTATION_ExAdv/mymul_test.ys
|
||||
:language: yoscrypt
|
||||
:caption: ``docs/resources/PRESENTATION_ExAdv/mymul_test.ys``
|
||||
|
||||
Handling constant inputs
|
||||
~~~~~~~~~~~~~~~~~~~~~~~~
|
||||
|
||||
- The special parameters ``_TECHMAP_CONSTMSK_<port-name>_`` and
|
||||
``_TECHMAP_CONSTVAL_<port-name>_`` can be used to handle constant input values
|
||||
to cells.
|
||||
- The former contains 1-bits for all constant input bits on the port.
|
||||
- The latter contains the constant bits or undef (x) for non-constant bits.
|
||||
- Example use-cases:
|
||||
|
||||
- Converting arithmetic (for example multiply to shift).
|
||||
- Identify constant addresses or enable bits in memory interfaces.
|
||||
|
||||
Example:
|
||||
|
||||
.. figure:: ../../images/res/PRESENTATION_ExAdv/mulshift.*
|
||||
:class: width-helper
|
||||
|
||||
.. literalinclude:: ../../resources/PRESENTATION_ExAdv/mulshift_map.v
|
||||
:language: verilog
|
||||
:caption: ``docs/resources/PRESENTATION_ExAdv/mulshift_map.v``
|
||||
|
||||
.. literalinclude:: ../../resources/PRESENTATION_ExAdv/mulshift_test.v
|
||||
:language: verilog
|
||||
:caption: ``docs/resources/PRESENTATION_ExAdv/mulshift_test.v``
|
||||
|
||||
.. literalinclude:: ../../resources/PRESENTATION_ExAdv/mulshift_test.ys
|
||||
:language: yoscrypt
|
||||
:caption: ``docs/resources/PRESENTATION_ExAdv/mulshift_test.ys``
|
||||
|
||||
Handling shorted inputs
|
||||
~~~~~~~~~~~~~~~~~~~~~~~
|
||||
|
||||
- The special parameters ``_TECHMAP_BITS_CONNMAP_`` and
|
||||
``_TECHMAP_CONNMAP_<port-name>_`` can be used to handle shorted inputs.
|
||||
- Each bit of the port correlates to an ``_TECHMAP_BITS_CONNMAP_`` bits wide
|
||||
number in ``_TECHMAP_CONNMAP_<port-name>_``.
|
||||
- Each unique signal bit is assigned its own number. Identical fields in the ``_TECHMAP_CONNMAP_<port-name>_`` parameters mean shorted signal bits.
|
||||
- The numbers 0-3 are reserved for ``0``, ``1``, ``x``, and ``z`` respectively.
|
||||
- Example use-cases:
|
||||
|
||||
- Detecting shared clock or control signals in memory interfaces.
|
||||
- In some cases this can be used for for optimization.
|
||||
|
||||
Example:
|
||||
|
||||
.. figure:: ../../images/res/PRESENTATION_ExAdv/addshift.*
|
||||
:class: width-helper
|
||||
|
||||
.. literalinclude:: ../../resources/PRESENTATION_ExAdv/addshift_map.v
|
||||
:language: verilog
|
||||
:caption: ``docs/resources/PRESENTATION_ExAdv/addshift_map.v``
|
||||
|
||||
.. literalinclude:: ../../resources/PRESENTATION_ExAdv/addshift_test.v
|
||||
:language: verilog
|
||||
:caption: ``docs/resources/PRESENTATION_ExAdv/addshift_test.v``
|
||||
|
||||
.. literalinclude:: ../../resources/PRESENTATION_ExAdv/addshift_test.ys
|
||||
:language: yoscrypt
|
||||
:caption: ``docs/resources/PRESENTATION_ExAdv/addshift_test.ys``
|
||||
|
||||
Notes on using techmap
|
||||
~~~~~~~~~~~~~~~~~~~~~~
|
||||
|
||||
- Don't use positional cell parameters in map modules.
|
||||
- You can use the ``$__``-prefix for internal cell types to avoid
|
||||
collisions with the user-namespace. But always use two underscores or the
|
||||
internal consistency checker will trigger on this cells.
|
||||
- Techmap has two major use cases:
|
||||
|
||||
- Creating good logic-level representation of arithmetic functions. This
|
||||
also means using dedicated hardware resources such as half- and full-adder
|
||||
cells in ASICS or dedicated carry logic in FPGAs.
|
||||
- Mapping of coarse-grain resources such as block memory or DSP cells.
|
||||
|
|
|
|||
Loading…
Add table
Add a link
Reference in a new issue