https://gcc.gnu.org/bugzilla/show_bug.cgi?id=100095
Richard Biener <rguenth at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Blocks| |85316
Version|unknown |11.0
Ever confirmed|0 |1
Status|UNCONFIRMED |NEW
Last reconfirmed| |2021-04-15
Keywords| |missed-optimization
--- Comment #1 from Richard Biener <rguenth at gcc dot gnu.org> ---
VRP optimizes this at -O2 but fails at -O3 where we fail to do some
final value replacement as we unswitch the loop nest on the b != 0 condition
which makes us end up with multiple exits which final_value_replacement_loop
doesn't like (it's somewhat artificial what we end up with - leaving
code commoning on the plate).
In the end the trigger of the missing optimization is unswitching.
Referenced Bugs:
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=85316
[Bug 85316] [meta-bug] VRP range propagation missed cases
