[Bug target/100775] ICE: in df_exit_block_bitmap_verify, at df-scan.c:4164 with -mthumb -fzero-call-used-regs=used

[qinzhao at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=100775

--- Comment #2 from qinzhao at gcc dot gnu.org ---
This is a bug in pass_zero_call_used_regs, when updating df after the zeroing
sequence is added in the epilogue of the function, we should call
"df_update_exit_block_uses" to update the reg use info in the exit block to
include all the regs that have been zeroed.

I think that this is a very general issue, should be fixed into both gcc12 and
gcc11.