[Bug rtl-optimization/125209] [16 Regression] ICE on valid code at -O1 and above on x86_64-linux-gnu: in simplify_subreg, at simplify-rtx.cc:8365

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=125209

--- Comment #7 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:8b146837cefcee5955687879a60fb6aa8accc11d

commit r16-9384-g8b146837cefcee5955687879a60fb6aa8accc11d
Author: Boudewijn van der Heide <[email protected]>
Date:   Sun May 10 21:46:48 2026 -0600

    [PATCH] combine: Check against CLOBBER in make_compound_operation_int
[PR125209]

    In combine_simplify_rtx, CLOBBER can be returned, which is propagated to
    make_compound_operation.  When make_compound_operation_int then calls
    simplify_subreg, it triggers a gcc_assert, because the mode is neither
inner,
    nor void. This results in an ICE.

    We fix this by checking if we got CLOBBER before calling simplify_subreg
from
    make_compound_operation and bail out; we return NULL_RTX.

    Testcase from the bug report by Zhendong Su.

    Bootstrapped and tested on x86_64-linux-gnu.

            PR rtl-optimization/125209

    gcc/
            * combine.cc (make_compound_operation_int): Return NULL_RTX if we
got CLOBBER.

    gcc/testsuite/
            * gcc.dg/pr125209.c: New test.

    Signed-off-by: Boudewijn van der Heide <[email protected]>
    (cherry picked from commit a33f80c6ed06037bd1d31680ae3152e362931f51)