[Bug target/116445] gcc.target/arm/unsigned-extend-2.c on Cortex-M55 and misses possible Cortex-M optimization

[avieira at gcc dot gnu.org via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=116445

--- Comment #4 from avieira at gcc dot gnu.org ---
Good point Kyrill! I was just merely comparing m3 to m55 but yes you are right,
with low overhead loops you don't need the r3 count... 

But -O2 also removes the r3, seems it does it at ud_dce, which doesn't get run
for -O1 and it looks like rtl_dce doesn't eliminat the subtract, probably not
able to handle cyclic dead code.