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Move (most of) ExOth and ExAdv slides
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Krystine Sherwin
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docs/source/yosys_internals/flow/command_ordering.rst
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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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