[Bug tree-optimization/126171] [16 Regression] miscompilation at -O2 on x86_64-linux-gnu

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=126171

--- Comment #10 from GCC Commits <cvs-commit at gcc dot gnu.org> ---
The releases/gcc-16 branch has been updated by Richard Biener
<[email protected]>:

https://gcc.gnu.org/g:a32b49435b4e3d6bb2510197f2ee4b3ff887cd62

commit r16-9382-ga32b49435b4e3d6bb2510197f2ee4b3ff887cd62
Author: Richard Biener <[email protected]>
Date:   Wed Jul 15 10:04:18 2026 +0200

    tree-optimization/126171 - SCEV and minus of INT_MIN

    The following fixes the existing mitigation against UB for handling
    of subtraction of the most negative value in a type.  We've only
    guarded the negation itself which is effective for avoiding UB in
    that but it does not help in fixing a wrong scev_direction that
    results from flipping the operation from minus to plus.  So the
    patch, instead of only promoting the negation to unsigned, promotes
    the whole operation.

            PR tree-optimization/126171
            * tree-scalar-evolution.cc (scev_dfs::add_to_evolution):
            Remove code argument.  Remove MINUS_EXPR handling here.
            (scev_dfs::follow_ssa_edge_binary): Likewise.
            (scev_dfs::follow_ssa_edge_expr): Handle MINUS_EXPR
            separately here, promoting the whole operation to unsigned
            instead of just the addend.

            * gcc.dg/pr126171-1.c: New testcase.
            * gcc.dg/torture/pr126171-2.c: Likewise.

    (cherry picked from commit 2fcbe075ec3b32f4a523ebae68a8a32381bb46a9)