[AArch64] Emit division using the Newton series

[AArch64] Emit division using the Newton series

2016-06-13  Evandro Menezes  <e.menezes@samsung.com>
            Wilco Dijkstra  <Wilco.Dijkstra@arm.com>

gcc/
	* config/aarch64/aarch64-protos.h
	(cpu_approx_modes): Add new member "division".
	(aarch64_emit_approx_div): Declare new function.
	* config/aarch64/aarch64.c
	(generic_approx_modes): New member "division".
	(exynosm1_approx_modes): Likewise.
	(xgene1_approx_modes): Likewise.
	(aarch64_emit_approx_div): Define new function.
	* config/aarch64/aarch64.md ("div<mode>3"): New expansion.
	* config/aarch64/aarch64-simd.md ("div<mode>3"): Likewise.
	* config/aarch64/aarch64.opt (-mlow-precision-div): Add new option.
	* doc/invoke.texi (-mlow-precision-div): Describe new option.

From-SVN: r237397