[Bug tree-optimization/123130] missed optimization for redundant instructions and compare instructions

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=123130

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
     Ever confirmed|0                           |1
           Keywords|                            |missed-optimization
             Blocks|                            |85316
   Last reconfirmed|                            |2025-12-15
             Status|UNCONFIRMED                 |NEW

--- Comment #1 from Richard Biener <rguenth at gcc dot gnu.org> ---
We're short-cutting the loops *d && *d != ':', losing the ability to remove
the redundant != 0 test on the exit from *d == 0.

We're also CSEing the != 0 test in unfortunate ways.  I'd say this is a
jump-threading / VRP issue in the end and lack of a "normalization" of
CFG vs. non-CFG jump conditions.


Referenced Bugs:

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=85316
[Bug 85316] [meta-bug] VRP range propagation missed cases