Sometimes the FF cell might be initialized during the map process, e.g.
some FPGA platforms (Anlogic Eagle and Lattice ECP5 for example) has
only a "SR" pin for a FF for async reset, that resets the FF to the
initial value, which means the async reset value should be set as the
initial value. In this case the DFFINIT pass shouldn't reinitialize it
to a different value, which will lead to error.
Add a "-noreinit" parameter for the safeguard. If a FF is not
technically initialized before DFFINIT pass, the default value should be
set to x.
Signed-off-by: Icenowy Zheng <icenowy@aosc.io>
On some platforms the string to initialize DFF might not be "high" and
"low", e.g. with Anlogic TD it's "SET" and "RESET".
Add a "-strinit" parameter for dffinit to allow specify the strings used
for high and low.
Signed-off-by: Icenowy Zheng <icenowy@aosc.io>
o Not all derived methods were marked 'override', but it is a great
feature of C++11 that we should make use of.
o While at it: touched header files got a -*- c++ -*- for emacs to
provide support for that language.
o use YS_OVERRIDE for all override keywords (though we should probably
use the plain keyword going forward now that C++11 is established)
Icenowy Zheng
Henner Zeller
Clifford Wolf
Marcus Comstedt