- FfData now keeps track of the module and underlying cell, if any (so
calling emit on FfData created from a cell will replace the existing cell)
- FfData implementation is split off to its own .cc file for faster
compilation
- the "flip FF data sense by inserting inverters in front and after"
functionality that zinit uses is moved onto FfData class and beefed up
to have dffsr support, to support more use cases
The main part is converting xilinx_dsp to recognize the new FF types
created in opt_dff instead of trying to recognize the patterns on its
own.
The fsm call has been moved upwards because the passes cannot deal with
$dffe/$sdff*, and other optimizations don't help it much anyway.
This adds support for infering more kinds of flip-flops:
- FFs with async set/reset and clock enable
- FFs with sync set/reset
- FFs with sync set/reset and clock enable
Some passes have been moved (and some added) in order for dff2dffs to
work correctly.
This gives us complete coverage of Virtex 6+ and Spartan 6 flip-flop
capabilities (though not latch capabilities). Older FPGAs also support
having both a set and a reset input, which will be handled at a later
data.
