Fixes a bug in the handling of the recently introduced $check cells.
Both $check and $print cells in clk2fflogic are handled by the same code
and the existing tests for that were only using $print cells. This
missed a bug where the additional A signal of $check cells that is not
present on $print cells was dropped due to a typo, rendering $check
cells non-functional.
Also updates the tests to explicitly cover both cell types such that
they would have detected the now fixed bug.
Right now neither `sat` nor `sim` have support for the `$check` cell.
For formal verification it is a good idea to always run either
async2sync or clk2fflogic which will (in a future commit) lower `$check`
to `$assert`, etc.
While `sim` should eventually support `$check` directly, using
`async2sync` is ok for the current tests that use `sim`, so this commit
also runs `async2sync` before running sim on designs containing
assertions.
This compares the write_smt2 output pretty much verbatim, which contains
auto generated private names and fixes an arbitrary ordering. The tested
functionality is also covered by SBY tests which actually interpret the
write_smt2 output using an SMT solver and thus are much more robust, so
we can safely remove this test.
The previous version could easily generate a large amount of padding
when the constant factor was significantly larger than the width of the
shift data input. This could lead to huge amounts of logic being
generated before then being optimized away at a huge performance and
memory cost.
Additionally and more critically, when the input width was not a
multiple of the constant factor, the input data was padded with 'x bits
to such a multiple before interspersing the 'x padding needed to align
the selectable windows to power-of-two offsets.
Such a final padding would not be correct for shifts besides $shiftx,
and the previous version did attempt to remove that final padding at the
end so that the native zero/sign/x-extension behavior of the shift cell
would be used, but since the last selectable window also got
power-of-two padding appended after the padding the code is trying to
remove got added, it did not actually fully remove it in some cases.
I changed the code to only add 'x padding between selectable windows,
leaving the last selectable window unpadded. This omits the need to add
final padding to a multiple of the constant factor in the first place.
In turn, that means the only 'x bits added are actually impossible to
select. As a side effect no padding is added when the constant factor is
equal to or larger than the width of the shift data input, also solving
the reported performance bug.
This fixes#4056