simplify_subreg can return VOIDmode const_int operand and will
cause ICE in simplify_gen_subreg when this operand is passed to it.

The patch prevents VOIDmode temporary from entering simplify_gen_subreg.
We can't process const_int operand any further, since outermode
is not an integer mode here.

2023-02-16  Uroš Bizjak  <ubizjak@gmail.com>

gcc/ChangeLog:

    PR target/108805
    * simplify_rtx.cc (simplify_context::simplify_subreg): Prevent
    VOIDmode const_int result from simplify_subreg from entering
    simplify_gen_subreg.

gcc/testsuite/ChangeLog:

    PR target/108805
    * gcc.dg/pr108805.c: New test.

Bootstrapped and regression tested on x86_64-linux-gnu {,-m32}.

OK for master and release branches?

Uros.