[ARM] ARM NEON support part 2/7: NEON support

[Paul Brook]

> This patch adds support for the NEON ISA, including RTL patterns which
> can be used for autovectorization (some current features may not yet be
> supported, however), and a (large) set of intrinsics. The latter are
> provided via an auto-generated header file, "arm_neon.h", which should
> provide the same capabilities as the header file of the same name
> supplied with ARM's proprietary compiler tools.

Ok, except a couple of tweaks, and if you haven't already done so you need to 
get a c++ maintainer to sign off on the new target hook.

> +   So that STM/LDM can be used on vectors in ARM registers, and the same
> +   memory layout will result as if VSTM/VLDM were used.
> +
> +   This memory format (in BE mode) is very likely to change in the future.
>  */

I think this memory format is now specified by the EABI.

You may want to change the comment to mention that it would be nice if teh 
vectorizer could generate array loads (vld1) rather than vector loads 
(vldr/vldm), but we don't currently support that.

> -  IWMMXT_BUILTIN2 (iwmmxt_wpackhss, WPACKHSS)
> +  IWMMXT_BUILTIN2 (iwmmxt_wpackhss,  WPACKHSS)

This looks like a spurious whitespace change.

Paul