gimplify: Allow declarations in recalculate_side_effects [PR126497]

The following testcase ICEs, because we decide to fold a comparison
into just one of its operands, we call recalculate_side_effects on that
and ICE on the assertion that it isn't called on anything unexpected
(here PARM_DECL).
Already some time ago we had to add an exception for SSA_NAME for the
same reason.
The tcc_declaration case is slightly different, TREE_SIDE_EFFECTS is
sometimes present on those if they are TREE_THIS_VOLATILE, but it is
something the FE should take care of when creating those decls, not
a business of the gimplifier.

2026-07-31  Jakub Jelinek  <jakub@redhat.com>

	PR middle-end/126497
	* gimplify.cc (recalculate_side_effects): Return for
	tcc_declaration.

	* gcc.dg/bitint-141.c: New test.

Reviewed-by: Andrea Pinski <andrew.pinski@oss.qualcomm.com>
(cherry picked from commit ca867fd9d5ace4ede8289dba9ae731e554bde618)