[PATCH][AArch64] Implemented vmul/vmux intrinsics

[Tim Northover]

Hi Ana,

> But to force vmul_n_f64, vmul_lane_f64, vmul_laneq_f64 legacy intrinsics to map to Neon scalar operations I had to add an aarch64 IR intrinsic.

I don't see why that's an issue in this case. Since floating-point
operations take place in FP-registers anyway, there should be no pair
with duplicated functionality. Could you give an example of some code
that wouldn't work as expected with a natural IR mapping?

Cheers.

Tim.