[arm][3/3] Implement fp16fml lane intrinsics

[arm][3/3] Implement fp16fml lane intrinsics

This patch implements the lane-wise fp16fml intrinsics.
There's quite a few of them so I've split them up from
the other simpler fp16fml intrinsics.

These ones expose instructions such as

vfmal.f16 Dd, Sn, Sm[<index>]  0 <= index <= 1
vfmal.f16 Qd, Dn, Dm[<index>]  0 <= index <= 3
vfmsl.f16 Dd, Sn, Sm[<index>]  0 <= index <= 1
vfmsl.f16 Qd, Dn, Dm[<index>]  0 <= index <= 3

These instructions extract a single half-precision
floating-point value from one of the source regs
and perform a vfmal/vfmsl operation as per the
normal variant with that value.

The nuance here is that some of the intrinsics want
to do things like:

float32x2_t vfmlal_laneq_low_u32 (float32x2_t __r, float16x4_t __a, float16x8_t __b, const int __index)

where the float16x8_t value of '__b' is held in a Q
register, so we need to be a bit smart about finding
the right D or S sub-register and translating the
lane number to a lane in that sub-register, instead
of just passing the language-level const-int down to
the assembly instruction.

That's where most of the complexity of this patch comes from
but hopefully it's orthogonal enough to make sense.

Bootstrapped and tested on arm-none-linux-gnueabihf as well as
armeb-none-eabi.

	* config/arm/arm_neon.h (vfmlal_lane_low_u32, vfmlal_lane_high_u32,
	vfmlalq_laneq_low_u32, vfmlalq_lane_low_u32, vfmlal_laneq_low_u32,
	vfmlalq_laneq_high_u32, vfmlalq_lane_high_u32, vfmlal_laneq_high_u32,
	vfmlsl_lane_low_u32, vfmlsl_lane_high_u32, vfmlslq_laneq_low_u32,
	vfmlslq_lane_low_u32, vfmlsl_laneq_low_u32, vfmlslq_laneq_high_u32,
	vfmlslq_lane_high_u32, vfmlsl_laneq_high_u32): Define.
	* config/arm/arm_neon_builtins.def (vfmal_lane_low,
	vfmal_lane_lowv4hf, vfmal_lane_lowv8hf, vfmal_lane_high,
	vfmal_lane_highv4hf, vfmal_lane_highv8hf, vfmsl_lane_low,
	vfmsl_lane_lowv4hf, vfmsl_lane_lowv8hf, vfmsl_lane_high,
	vfmsl_lane_highv4hf, vfmsl_lane_highv8hf): New sets of builtins.
	* config/arm/iterators.md (VFMLSEL2, vfmlsel2): New mode attributes.
	(V_lane_reg): Likewise.
	* config/arm/neon.md (neon_vfm<vfml_op>l_lane_<vfml_half><VCVTF:mode>):
	New define_expand.
	(neon_vfm<vfml_op>l_lane_<vfml_half><vfmlsel2><mode>): Likewise.
	(vfmal_lane_low<mode>_intrinsic,
	vfmal_lane_low<vfmlsel2><mode>_intrinsic,
	vfmal_lane_high<vfmlsel2><mode>_intrinsic,
	vfmal_lane_high<mode>_intrinsic, vfmsl_lane_low<mode>_intrinsic,
	vfmsl_lane_low<vfmlsel2><mode>_intrinsic,
	vfmsl_lane_high<vfmlsel2><mode>_intrinsic,
	vfmsl_lane_high<mode>_intrinsic): New define_insns.

	* gcc.target/arm/simd/fp16fml_lane_high.c: New test.
	* gcc.target/arm/simd/fp16fml_lane_low.c: New test.

From-SVN: r256540