This patch sets the nothrow flag for various calls to internal functions
that are not inherently NOTHROW (and so can't be declared that way in
internal-fn.def) but that are used in contexts that can guarantee
NOTHROWness.

2017-08-29  Richard Sandiford  <richard.sandiford@linaro.org>

gcc/
	* gimplify.c (gimplify_call_expr): Copy the nothrow flag to
	calls to internal functions.
	(gimplify_modify_expr): Likewise.
	* tree-call-cdce.c (use_internal_fn): Likewise.
	* tree-ssa-math-opts.c (pass_cse_reciprocals::execute): Likewise.
	(convert_to_divmod): Set the nothrow flag.
	* tree-if-conv.c (predicate_mem_writes):  Likewise.
	* tree-vect-stmts.c (vectorizable_mask_load_store): Likewise.
	(vectorizable_call): Likewise.
	(vectorizable_store): Likewise.
	(vectorizable_load): Likewise.
	* tree-vect-patterns.c (vect_recog_pow_pattern): Likewise.
	(vect_recog_mask_conversion_pattern): Likewise.

From-SVN: r251401