Now comes *after* example_synth, with references back to it.
Includes some minor adjustment to the `fifo.ys` script to better demonstrate the `select` command.
Still needs an updated section on `show`.
Also includes some other minor updates.
Replace leftover `opt` example source/images with examples specific to the `opt_*` pass.
Currently has images for `opt_expr`, `opt_merge`, `opt_muxtree`, and `opt_share`.
Also includes some other TODO updates.
At the moment the only thing it allows is redirecting `$print` cell
output in a context-dependent manner. In the future, it will allow
customizing handling of `$check` cells (where the default is to abort),
of out-of-range memory accesses, and other runtime conditions with
effects.
This context object also allows a suitably written testbench to add
Verilog-compliant `$time`/`$realtime` handling, albeit it involves
the ceremony of defining a `performer` subclass. Most people will
want something like this to customize `$time`:
int64_t time = 0;
struct : public performer {
int64_t *time_ptr;
int64_t time() const override { return *time_ptr; }
} performer = { &time };
p_top.step(&performer);
This approach to tracking simulation time was a mistake that I did not
catch in review. It has several issues:
1. There is absolutely no requirement to call `step()`, as it is
a convenience function. In particular, `steps` will not be
incremented in submodules if `-noflatten` is used.
2. The semantics of `steps` does not match that of the Verilog `$time`
construct.
3. There is no way to make the semantics of `%t` match that of Verilog.
4. The `module` interface is intentionally very barebones. It is little
more than a container for three method pointers, `reset`, `eval`,
and `commit`. Adding ancillary data to it goes against this.
If similar functionality is introduced again it should probably be
a variable that is global per toplevel design using some object that is
unique for an entire hierarchy of modules, and ideally exposed via
the C API. For now, it is being removed (in this commit) and (in next
commit) the capability is being reintroduced through a context object
that can be specified for `eval()`.
This commit achieves three roughly equally important goals:
1. To bring the rendering code in kernel/fmt.cc and in cxxrtl.h as close
together as possible, with an ideal of only having the bigint library
as the difference between the render functions.
2. To make the treatment of `$time` and `$realtime` in CXXRTL closer to
the Verilog semantics, at least in the formatting code.
3. To change the code generator so that all of the `$print`-to-`string`
conversion code is contained inside of a closure.
There are two reasons to aim for goal (3):
a. Because output redirection through definition of a global ostream
object is neither convenient nor useful for environments where
the output is consumed by other code rather than being printed on
a terminal.
b. Because it may be desirable to, in some cases, ignore the `$print`
cells that are present in the netlist based on a runtime decision.
This is doubly true for an upcoming `$check` cell implementing
assertions, since failing a `$check` would by default cause a crash.
This avoids having to devirtualize them later to get performance back,
and simplifies the code a bit.
The change is prompted by the desire to add a similar observer object
to `eval()`, and a repeated consideration of whether the dispatch on
these should be virtual in first place.
The name `on_commit` was terrible since it would not be called, as one
may conclude from the name, on each `commit()`, but only whenever that
method actually updates a value.
More `literalinclude` and references to source.
Adding `example_show.ys` and `example_lscd.ys`.
Rename `example_00` et al to `example_first` et al.
Also some other minor tidying.
Working on `opt.rst`.
Replace the hardcoded `opt` psuedo code listing with a `literalinclude` from `/cmd/opt.rst`.
Reorder and update `opt_*` list to match current `opt`.
Expand sub-section titles with the function of the pass (keeping the `:cmd:ref:` part at the end to prevent the Esbonio error in vscode when a heading starts with a directive).
Move comments about `clean` and `;;` being aliases into final `opt` subsection.
Also renames `Test suites` -> `Testing Yosys`.
Adds note on `+/`.
Clarifies that we can't entirely skip loading `cells_sim.v`, and then mentions it again later once we need it.
More on final steps (and synthesis outputs).
These are useful for formal verification with SBY where they can be used
to display solver chosen `rand const reg` signals and signals derived
from those.
The previous error message for non-constant initial $display statements
is downgraded to a log message. Constant initial $display statements
will be shown both during elaboration and become part of the RTLIL so
that the `sim` output is complete.
This allows tools like SBY to capture the $display output independent
from anything else sim might log. Additionally it provides source and
hierarchy locations for everything printed.
N. Engelhardt
Miodrag Milanovic
Krystine Sherwin
Martin Povišer
Catherine
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Jannis Harder
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