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Docs: Reflow line length

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Krystine Sherwin 2024-05-03 13:38:01 +12:00
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docs/source/using_yosys/synthesis/extract.rst
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@ -1,12 +1,12 @@
The extract pass
----------------
- Like the `techmap` pass, the `extract` pass is called with a
map file. It compares the circuits inside the modules of the map file with the
design and looks for sub-circuits in the design that match any of the modules
in the map file.
- If a match is found, the `extract` pass will replace the matching
subcircuit with an instance of the module from the map file.
- Like the `techmap` pass, the `extract` pass is called with a map file. It
compares the circuits inside the modules of the map file with the design and
looks for sub-circuits in the design that match any of the modules in the map
file.
- If a match is found, the `extract` pass will replace the matching subcircuit
with an instance of the module from the map file.
- In a way the `extract` pass is the inverse of the techmap pass.
.. todo:: add/expand supporting text, also mention custom pattern matching and
@ -68,23 +68,23 @@ The wrap-extract-unwrap method
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Often a coarse-grain element has a constant bit-width, but can be used to
implement operations with a smaller bit-width. For example, a 18x25-bit multiplier
can also be used to implement 16x20-bit multiplication.
implement operations with a smaller bit-width. For example, a 18x25-bit
multiplier can also be used to implement 16x20-bit multiplication.
A way of mapping such elements in coarse grain synthesis is the
wrap-extract-unwrap method:
wrap
Identify candidate-cells in the circuit and wrap them in a cell with a
constant wider bit-width using `techmap`. The wrappers use the same
parameters as the original cell, so the information about the original width
of the ports is preserved. Then use the `connwrappers` command to
connect up the bit-extended in- and outputs of the wrapper cells.
constant wider bit-width using `techmap`. The wrappers use the same parameters
as the original cell, so the information about the original width of the ports
is preserved. Then use the `connwrappers` command to connect up the
bit-extended in- and outputs of the wrapper cells.
extract
Now all operations are encoded using the same bit-width as the coarse grain
element. The `extract` command can be used to replace circuits with
cells of the target architecture.
element. The `extract` command can be used to replace circuits with cells of
the target architecture.
unwrap
The remaining wrapper cell can be unwrapped using `techmap`.