gimplify: Fix ICE in recalculate_side_effects [PR113228]

The following testcase ICEs during regimplificatgion since the addition of
(convert (eqne zero_one_valued_p@0 INTEGER_CST@1))
simplification.  That simplification is novel in the sense that in
gimplify_expr it can turn an expression (comparison in particular) into
a SSA_NAME.  Normally when gimplify_expr sees originally a SSA_NAME, it does
        case SSA_NAME:
          /* Allow callbacks into the gimplifier during optimization.  */
          ret = GS_ALL_DONE;
          break;
and doesn't try to recalculate side effects because of that, but in this
case gimplify_expr normally enters the:
        default:
          switch (TREE_CODE_CLASS (TREE_CODE (*expr_p)))
            {
            case tcc_comparison:
then does
                      *expr_p = gimple_boolify (*expr_p);
and then
                          *expr_p = fold_convert_loc (input_location,
                                                      org_type, *expr_p);
with this new match.pd simplification turns that tcc_comparison class
into SSA_NAME.  Unlike the outer SSA_NAME handling though, this falls
through into
          recalculate_side_effects (*expr_p);

        dont_recalculate:
          break;
but unfortunately recalculate_side_effects doesn't handle SSA_NAME and ICEs
on it.
SSA_NAMEs don't ever have TREE_SIDE_EFFECTS set on those, so the following
patch fixes it by handling it similarly to the tcc_constant case.

2024-01-08  Jakub Jelinek  <jakub@redhat.com>

	PR tree-optimization/113228
	* gimplify.cc (recalculate_side_effects): Do nothing for SSA_NAMEs.

	* gcc.c-torture/compile/pr113228.c: New test.