Stumbled over this as we recently got a sm_89 card.

-march-map= is mostly a future proof method for user to ensure to use 
always the best code gen for a specific card - without needing to know 
which GCC version added support for what --march=sm_... (or -misa=sm_... 
- those are aliases).

sm_89 was added in CUDA 11.8 (ptx isa 7.8) and sm_90a in CUDA 12.0 (ptx 
isa 8.0) but that's just FYI as -march-map=sm_xx, xx >= 80 is mapping to 
-march=sm_80 and implies -mptx=7.0 (i.e. ptx isa 7.0, added in CUDA 
11.0); hence, any CUDA 11.0+ will do.

OK for mainline?

Tobias