It turns out that it is possible for an otherwise constant net
mux to be non-constant if there is a force that can drive the
net. This can be detected as an l-value reference to an otherwise
constant selector.
By not creating Nexus objects until necessary, we avoid creating a
lot of spurious objects. In fact, it is true that almost every
link that is created and connected to another link will create a
spurious Nexus object without this patch.
Continue cleaning up shadowed variables, flagged by turning on -Wshadow.
No intended change in functionality. Patch looks right, and is tested
to compile and run on my machine. No regressions in test suite.
Remove redundant pointer to the containing NetPins object by keeping
the pointer only in the first Link (pin 0) of an array of links. In
this link, replace the pin number with the NetPins pointer, and set
a pins_zero_ flag to indicate that this has happened. This way, only
the first pin in a Link array will have the pointer to the NetPins
that contains the array, and the pointer takes up practically no space
at all.
convert the continuous assign elaboration to use elaborate_expr
and synthesize methods instead of the elaborate_net methods of
PExpr. This exposes problems with the synthesize methods, but it
is a better way to do it.
When driving an input port to a module, watch out for the case where
the net is also driven within the instance. If this is the case, take
pains to make sure what goes on in the instance doesn't leak out
through the input port. Add a BUFZ (continuous assignment) to isolate
the context from internal driving.
The NetBranch object is connected, but not like an object, so the
NetPins object base class is factored out from NetObj to handle the
connectivity, and the NetBranch class uses the NetPins to connect a
branch.
Also, account for the fact that nets with a discipline are by default
real-valued.
This patch fixes a delete[] vs free problem in the NexusSet
class. The items_ array was being allocated with malloc/realloc
and freed with delete[]. The quick fix was to replace delete[]
with a call to free(). A better fix would probably be to rework
the class to use a vector.
Padding and continuous assignment caused problems if the continuous
assignment includes a delay. The problem is that the padding was
not necessarily included in the delay. Rework the elaboration to
make sure the padding is indeed included in the delay.
Stephen Williams
Larry Doolittle
Cary R
steve