Remove unreachable returns

Remove unreachable returns

This removes unreachable return statements as diagnosed by
the -Wunreachable-code patch.  Some cases are more obviously
an improvement than others - in fact some may get you the idea
to replace them with gcc_unreachable () instead, leading to
cases of the 'Remove unreachable gcc_unreachable () at the end
of functions' patch.

2021-11-25  Richard Biener  <rguenther@suse.de>

	* vec.c (qsort_chk): Do not return the void return value
	from the noreturn qsort_chk_error.
	* ccmp.c (expand_ccmp_expr_1): Remove unreachable return.
	* df-scan.c (df_ref_equal_p): Likewise.
	* dwarf2out.c (is_base_type): Likewise.
	(add_const_value_attribute): Likewise.
	* fixed-value.c (fixed_arithmetic): Likewise.
	* gimple-fold.c (gimple_fold_builtin_fputs): Likewise.
	* gimple-ssa-strength-reduction.c (stmt_cost): Likewise.
	* graphite-isl-ast-to-gimple.c
	(gcc_expression_from_isl_expr_op): Likewise.
	(gcc_expression_from_isl_expression): Likewise.
	* ipa-fnsummary.c (will_be_nonconstant_expr_predicate):
	Likewise.
	* lto-streamer-in.c (lto_input_mode_table): Likewise.

gcc/c-family/
	* c-opts.c (c_common_post_options): Remove unreachable return.
	* c-pragma.c (handle_pragma_target): Likewise.
	(handle_pragma_optimize): Likewise.

gcc/c/
	* c-typeck.c (c_tree_equal): Remove unreachable return.
	* c-parser.c (get_matching_symbol): Likewise.

libgomp/
	* oacc-plugin.c (GOMP_PLUGIN_acc_default_dim): Remove unreachable
	return.