[Bug target/105496] Comparison optimizations result in unnecessary cmp instructions

rguenth at gcc dot gnu.org gcc-bugzilla@gcc.gnu.org
Fri May 6 06:06:48 GMT 2022


https://gcc.gnu.org/bugzilla/show_bug.cgi?id=105496

Richard Biener <rguenth at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Target|                            |x86_64-*-*
           Keywords|                            |missed-optimization
     Ever confirmed|0                           |1
             Status|UNCONFIRMED                 |NEW
   Last reconfirmed|                            |2022-05-06
            Version|unknown                     |12.0

--- Comment #1 from Richard Biener <rguenth at gcc dot gnu.org> ---
Confirmed.  We canonicalize x < 11 to x <= 10 and on GIMPLE we don't have CC
flags and thus we cannot combine the two compares (we could maybe invent
switch (x CC_EXPR 11) { case LT: .. }).  So _maybe_ compare elimination on RTL
is needed to do the job here.


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