[Bug tree-optimization/123061] [13/14/15 Regression] wrong code at -O3 with -ffinite-loops on x86_64-linux-gnu since r12-3313

[cvs-commit at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=123061

--- Comment #8 from GCC Commits <cvs-commit at gcc dot gnu.org> ---
The releases/gcc-15 branch has been updated by Richard Biener
<rguenth@gcc.gnu.org>:

https://gcc.gnu.org/g:95ce1bf40d85fb033b54cad10912830a3e92df07

commit r15-10970-g95ce1bf40d85fb033b54cad10912830a3e92df07
Author: Richard Biener <rguenther@suse.de>
Date:   Wed Jan 7 10:23:22 2026 +0100

    tree-optimization/123061 - invalid hoisting of division

    The following fixes the computation of always-exeecuted-in in the LIM
    pass which was enhanced to handle inner loops in a better way but
    in this process ended up setting inner loop always-executed-in state
    based on outer loop analysis, which is wrong because an inner loop
    block needs to be proven to be always executed for all inner loop
    iterations as well, not only for all outer loop iterations.

    The fix is to iterate over inner loops first and when processing
    an outer loop only update always-executedness if a block belongs
    to the very same loop or an immediately nested loop and always
    executed inside that.

            PR tree-optimization/123061
            PR tree-optimization/123636
            * tree-ssa-loop-im.cc (fill_always_executed_in_1): Change
            outer-to-inner to inner-to-outer iteration.  Update inner
            loop state only when always executed in an immediately
            nested loop.

            * gcc.dg/torture/pr123061.c: New testcase.
            * gcc.dg/torture/pr123636.c: Likewise.
            * gcc.dg/tree-ssa/ssa-lim-26.c: Likewise.

    (cherry picked from commit e48704694d686de1aaaaf934c04a2eda1a6033cb)