Add a type_has_mode_precision_p helper function

Add a type_has_mode_precision_p helper function

...to replace instances of:

    TYPE_PRECISION (t) == GET_MODE_PRECISION (TYPE_MODE (t))

These conditions would need to be rewritten with variable-sized
modes anyway.

2017-08-21  Richard Sandiford  <richard.sandiford@linaro.org>

gcc/
	* tree.h (type_has_mode_precision_p): New function.
	* convert.c (convert_to_integer_1): Use it.
	* expr.c (expand_expr_real_2): Likewise.
	(expand_expr_real_1): Likewise.
	* fold-const.c (fold_single_bit_test_into_sign_test): Likewise.
	* match.pd: Likewise.
	* tree-ssa-forwprop.c (simplify_rotate): Likewise.
	* tree-ssa-math-opts.c (convert_mult_to_fma): Likewise.
	* tree-tailcall.c (process_assignment): Likewise.
	* tree-vect-loop.c (vectorizable_reduction): Likewise.
	* tree-vect-patterns.c (vect_recog_vector_vector_shift_pattern)
	(vect_recog_mult_pattern, vect_recog_divmod_pattern): Likewise.
	* tree-vect-stmts.c (vectorizable_conversion): Likewise.
	(vectorizable_assignment): Likewise.
	(vectorizable_shift): Likewise.
	(vectorizable_operation): Likewise.
	* tree-vrp.c (register_edge_assert_for_2): Likewise.

git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/trunk@251231 138bc75d-0d04-0410-961f-82ee72b054a4