The source location is set to the place where `In`/`Out` was created.
The source location of the instantiation is tracked but overwritten;
we will need to change the internal structure storing those to be able
to include both.
Fixes#1085.
This closes#721 by implementing get_async_ff_sync() using FDPE
primitives to obtain exactly the netlist that we want. This consits
of a chain of N FPDEs (by default N = 2) with all their PRE pins
connected to the reset for a positive edge reset or to the ~reset
for a negative edge reset. The D pin of the first FDPE in the chain
is connected to GND.
To make timing analysis work correctly, two new attributes are
introduced: amaranth.vivado.false_path_pre and
amaranth.vivado.max_delay_pre. These work similarly to
amaranth.vivado.false_path and amaranth.vivado.max_delay, but affect
only the PRE pin, which is what is needed for this synchronizer.
The TCL has been modified to generate constraints using these
attributes, and there are comments explaining how to use the attributes
directly in an XDC file in case the user wants to manage their XDC
file manually instead of using the TCL.
This subclassing is unnecessary and makes downstream code more complex.
In the new IR, they are unified into cells with the same name anyway.
Even before that, this change simplifies things.
This commit also contains a related semantic change: it adds `Shape`
and `ShapeCastable` to the `__all__` list in `amaranth.hdl`. This is
consistent with the policy that is laid out in the new documentation,
which permits such additions without notice.
Co-authored-by: mcclure <mcclure@users.noreply.github.com>
This change completes commit 9dc0617e and makes all the tests pass.
It corresponds with the ongoing langauge reference documentation effort.
Fixes#781.
Reexports of `amaranth.utils` functions are removed from
`amaranth._utils` to avoid a circular import issue (for `deprecated`).
Since this is a private module, this should not be a problem.
This ensures things like `Const(1.5)` raise an error.
`int(operator.index())` is used since `operator.index(True)` on Python
3.9 and earlier returns `True` instead of `1`.
