(ext_shift_insns, ext_shift_amounts): new arrays.

(gen_ashift_hi, gen_shifty_hi_op, shl_and_kind): new functions.
rtx_equal_function_value_matters: declare.
(shl_and_length, shl_and_src_length, gen_shl_and): new functions.
(shl_sext_kind, shl_sext_length, gen_shl_sext): new functions.

From-SVN: r12726