Comment by bbbbbr
Not the parent, but I have a take. :)
For GBDK-2020 we've been using the 6502 support in SDCC to support the NES as a target console for about 2 years alongside the existing Game Boy and SMS/Game Gear targets.
The 6502 port has been usable, but doesn't seem fully mature. There has been a lot of code churn for it during the last 12 months compared to the z80/sm83 ports as it gets improved. Recently (their recommended pre-release build 15614) this seems to have resulted in some breaking regressions that we haven't fully tracked down.
Perhaps this port is getting less testing coverage than the z80/sm83 port. Unsure. The majority of the 6502 work seems to be done by a newer member of their team, with the longer term members seeming to be somewhat hands-off. That might be an additional factor.
Edit: BTW, the 6502 port in SDCC at build 15267 (~4.5.0+) has been reasonably stable and usable, and is what we based our last GBDK-2020 release on (6 months ago).
Ah thank you, that is all very helpful - I've been using 4.4.0 which is fine for Z80 code, but yeah had the feeling 6502 code generation could be improved.