SystemVerilog defines different levels of type compatibility.
* Matching
* Equivalent
* Assignment compatible
* Cast compatible
At the moment the `nettype_t` has only one type compatibility test. It is
used to check assignment compatibility when assigning to a dynamic array,
queue or class.
The current implementation rejects a few cases that should allowed and
allows a few cases that should be rejected.
Dynamic arrays and queues are assignment compatible if their element types
are compatible. And two packed types are equivalent if they are both
2-state or 4-state, both signed or unsigned and have the same packed with.
In the current implementation the sign is not considered and instead of
checking if the packed width is the same it checks that the dimensions are
identical.
Signed-off-by: Lars-Peter Clausen <lars@metafoo.de>
The `netdarray_t` type implements the `packed_width()` method by returning
the packed width of the element type. It is the only non-packed type that
implements the method.
This triggers an assert in the vlog95 backend for tasks with dynamic array
typed parameters. And while the vlog95 backend does not support dynamic
array types it should not result in a crash, just an error message.
The only place that relies on the behavior that the packed width of the
element type is returned is in the vvp backend where variable declarations
are generated. Update that code to query the packed width of the element
type instead and then remove the `packed_width()` implementation for the
`netdarray_t` type.
This fixes the assert in the vlog95 backend. But it is also nicer from an
architectural perspective as this brings the type in line with the other
types in terms of behavior.
Signed-off-by: Lars-Peter Clausen <lars@metafoo.de>
Commit e1870acfac ("Return the correct value when a queue or darray
references an undefined element") added support for specifying the width of
the vector elements stored in a queue or dynamic array, so that an
out-of-bounds access can create a word with the right width.
To get the element width of a queue or dynamic array it uses the
`packed_width()` method. But this method is only implemented for
`netqueue_t` and returns always 1 for dynamic arrays. As a result
out-of-bounds access on a dynamic array will push a vector of the wrong
width onto the stack if the vector element is wider than 1 bit. This will
usually trigger an assert in vvp.
Fix this by moving the `packed_width()` method implementation from
`netqueue_t` to its base class `netdarray_t` so that it works for all types
of dynamic arrays.
Signed-off-by: Lars-Peter Clausen <lars@metafoo.de>
Lars-Peter Clausen
Cary R
Stephen Williams
Arun Persaud