The commit observer is a structure containing a callback that is invoked
whenever the `commit()` method changes a wire or a memory. This allows
code external to the compiled netlist to react to changes in the design
state in a very efficient way. One example of how this feature can be
used is an efficient implementation of record/replay.
Note that the VCD writer does not benefit from this feature because it
must be able to react to changes in any debug items and not just those
that contain design state.
While the VCD format separates the timescale and the timestep (likely
to allow representing the timestep with a small integer type), time in
CXXRTL is represented using a uniform 96-bit number, which allows for
a ±100 year range at femtosecond resolution.
The implementation uses `value<96>`, which provides fast arithmetic and
comparison operations, as well as conversion to/from a more common
representation of integer seconds plus femtoseconds.
Split hardware mapping from `fifo.ys` into `fifo_map.ys`. Reduces size of `fifo.out` log and allows separate yosys calls in the makefile.
Some tidy up and minor changes in `fifo.ys` for better discussion.
Filled out note on `clean` (changed from `opt_clean`) and introduced `;;`.
Highlighted `$memrd` and added a paragraph about it.
More detail on the flatten and merging of `fifo_reader` block.
Brief discussion on the changes from `$memrd` to `$memrd_v2`.
Split coarse grain representation into 4 parts, loosely: fsm/opt, other optimizations/techmap/memory_dff, DSPs, alumacc/memory -nomap.
Split hardware mapping into subsections as well: memory blocks (map_ram and map_ffram), arithmetic (map_gates), FFs (map_ffs), LUTs (map_luts and briefly abc), and other (map_cells and a note on hilomap and iopadmap).
Also add `-T` flag to Yosys call to remove footer from log output.
Added highlighting in (most) schematics.
Written down to end of coarse-grain, with a couple of TODOs for filling in gaps.
Includes `techmap_synth.rst` stub.
Fifo code based on SBY quick start.
Instead of showing the full design we are (currently) focusing on a single output (rdata), using `%ci*` to get the subcircuit it relies on.
Overall structure in place to match the iCE40 flow.
Still needs a new example design, and more text for the later sections (which the counter doesn't cover).
Updates code examples, removing `counter_outputs.ys` in favour of a single script. Also adds a .gitignore for the output file `synth.v`.
`example_synth.rst` still pending updated example.
Prior to this fix, the `CxxrtlBackend` used the entire path for the include
directive when a separated interface file is generated (via the `-header`
option). This commit updates the code to use the base name of the interface
file.
Since the C++11 standard is used by default, we cannot take advantage of
the `std::filesystem` to get the basename.
Moved the last files out of the resources directory.
Some tidy up/reformatting of the extensions to allow literalincludes from `my_cmd.cc`.
Most (all?) of the getting started guidelines file is either in the quick guide section, or sections referenced by it. Instead of including it verbatim, we'll instead just leave a reference to it but then jump straight into the quick guide.
Include an image for the absval generated module. Still needs more surrounding text but it's good enough for now.
Also includes some other minor tidying, including removing the no longer used abc_01 code example.
Includes comparison of `abc` v `abc9`. Also creates a new subsection of the
yosys internals for extending yosys (moving the previous extensions.rst into it).
Co-authored-by: Lofty <dan.ravensloft@gmail.com>
Catherine
Martin Povišer
Dag Lem
Krystine Sherwin
Miodrag Milanovic
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