This is the mail archive of the
gcc-bugs@gcc.gnu.org
mailing list for the GCC project.
[Bug target/50256] AVR GCC - several unnecessary register moves
- From: "gjl at gcc dot gnu.org" <gcc-bugzilla at gcc dot gnu dot org>
- To: gcc-bugs at gcc dot gnu dot org
- Date: Sat, 03 Sep 2011 12:34:49 +0000
- Subject: [Bug target/50256] AVR GCC - several unnecessary register moves
- Auto-submitted: auto-generated
- References: <bug-50256-4@http.gcc.gnu.org/bugzilla/>
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=50256
Georg-Johann Lay <gjl at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Target|atmel avr |avr
CC| |gjl at gcc dot gnu.org
--- Comment #3 from Georg-Johann Lay <gjl at gcc dot gnu.org> 2011-09-03 12:34:49 UTC ---
Supported versions of GCC are 4.4 upward at the moment.
Your C-code does not show a call to MulU3U3S3 and the constants 167772 resp.
100000 occur nowhere. Please follow http://gcc.gnu.org/bugs/#need when
reporting bugs. Thanks.
Notice that early clobber forces moves. Moreover, some value is passed in r20
but you clobber that register so that register must be freed i.e. that forces a
move, too. Maybe you want your function static inline. Also notice that if you
have MUL, you always have MOVW. You don't need to save/restore __tmp_reg__. You
don't need to save __zero_reg__. It is sufficient to CLR __zero_reg__ after you
are done.
Last not least, you arithmetic apprears to be wrong because you add at most 3
bytes and lose the carries above.