Hi All,

This patch adds the expander support for supporting autovectorization of complex number operations
such as Complex addition with a rotation along the Argand plane.  This also adds support for complex
FMA.

The instructions are described in the ArmARM [1] and are available from Armv8.3-a onwards.

Concretely, this generates

f90:
	mov	x3, 0
	.p2align 3,,7
.L2:
	ldr	q0, [x0, x3]
	ldr	q1, [x1, x3]
	fcadd	v0.2d, v0.2d, v1.2d, #90
	str	q0, [x2, x3]
	add	x3, x3, 16
	cmp	x3, 3200
	bne	.L2
	ret

now instead of

f90:
	mov	x4, x1
	mov	x1, x2
	add	x3, x4, 31
	add	x2, x0, 31
	sub	x3, x3, x1
	sub	x2, x2, x1
	cmp	x3, 62
	mov	x3, 62
	ccmp	x2, x3, 0, hi
	bls	.L5
	mov	x2, x4
	add	x3, x0, 3200
	.p2align 3,,7
.L3:
	ld2	{v2.2d - v3.2d}, [x0], 32
	ld2	{v4.2d - v5.2d}, [x2], 32
	cmp	x0, x3
	fsub	v0.2d, v2.2d, v5.2d
	fadd	v1.2d, v4.2d, v3.2d
	st2	{v0.2d - v1.2d}, [x1], 32
	bne	.L3
	ret
.L5:
	add	x6, x0, 8
	add	x5, x4, 8
	add	x2, x1, 8
	mov	x3, 0
	.p2align 3,,7
.L2:
	ldr	d1, [x0, x3]
	ldr	d3, [x5, x3]
	ldr	d0, [x6, x3]
	ldr	d2, [x4, x3]
	fsub	d1, d1, d3
	fadd	d0, d0, d2
	str	d1, [x1, x3]
	str	d0, [x2, x3]
	add	x3, x3, 16
	cmp	x3, 3200
	bne	.L2
	ret

For complex additions with a 90* rotation along the Argand plane.

[1] https://developer.arm.com/docs/ddi0487/latest/arm-architecture-reference-manual-armv8-for-armv8-a-architecture-profile

Bootstrap and Regtest on aarch64-none-linux-gnu, arm-none-gnueabihf and x86_64-pc-linux-gnu
are still on going but previous patch showed no regressions.

The instructions have also been tested on aarch64-none-elf and arm-none-eabi on a Armv8.3-a model
and -march=Armv8.3-a+fp16 and all tests pass.

Ok for trunk?

Thanks,
Tamar

gcc/ChangeLog:

2018-11-11  Tamar Christina  <tamar.christina@arm.com>

	* config/aarch64/aarch64-simd.md (aarch64_fcadd<rot><mode>,
	fcadd<rot><mode>3, aarch64_fcmla<rot><mode>,
	fcmla<rot><mode>4): New.
	* config/aarch64/aarch64.h (TARGET_COMPLEX): New.
	* config/aarch64/iterators.md (UNSPEC_FCADD90, UNSPEC_FCADD270,
	UNSPEC_FCMLA, UNSPEC_FCMLA90, UNSPEC_FCMLA180, UNSPEC_FCMLA270): New.
	(FCADD, FCMLA): New.
	(rot, rotsplit1, rotsplit2): New.
	* config/arm/types.md (neon_fcadd, neon_fcmla): New.

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