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 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.
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.
In preparation for substantial expansion of CXXRTL's runtime, this commit
reorganizes the files used by the implementation. Only minimal changes are
required in a consumer.
First, change:
-I$(yosys-config --datdir)/include
to:
-I$(yosys-config --datdir)/include/backends/cxxrtl/runtime
Second, change:
#include <backends/cxxrtl/cxxrtl.h>
to:
#include <cxxrtl/cxxrtl.h>
(and do the same for cxxrtl_vcd.h, etc.)
We add a new flow graph node type, PRINT_SYNC, as they don't get handled
with regular CELL_EVALs. We could probably move this grouping out of
the dump method.
Before this commit, values, wires, and memories with an initializer
were value-initialized in emitted C++ code. After this commit, all
values, wires, and memories are default-initialized, and the default
constructor of generated modules calls the reset() method, which
assigns the members that have an initializer.
Public wires may alias buffered internal wires, so keep BUFFERED
wires in debug information even if they are private. Debug items are
only created for public wires, so this does not otherwise affect how
debug information is emitted.
Fixes#2540.
Fixes#2841.
While this helper is already useful to squash sequential initializations
into one in cxxrtl, its main purpose is to squash overlapping masked memory
initializations (when they land) and avoid having to deal with them in
cxxrtl runtime.
