libdvbcsa: AArch64 support

[glenvt18]

This follows #1053.

[glenvt18]

Update, version change. Fixes glenvt18/libdvbcsa#1. Can anyone build and test it on RPi2/3 with the latest LibreELEC toolchain? Testing instructions: #1053 (comment)

[MilhouseVH]

This builds fine on RPi, RPi2 and Generic.

However performance is slightly worse on an RPi3 - down from ~135MB/s to ~131MB/s:
new: http://pastebin.com/raw/qREwHNCB
old: http://pastebin.com/raw/gEMa3skW

[glenvt18]

@MilhouseVH I see

libdvbcsa 1613dd4 (post-#1058) on RPi3 (kodi not running):

in your paste, but the right hash is glenvt18/libdvbcsa@7360578 (like in this commit). Is it a typo?

[MilhouseVH]

Sorry fat fingers - I was simultaneously looking at this PR and also #1053, and I copied the rev from #1053. The "post-#1058" rev should have been 7360578 (and in fact is, when I look at the package.mk in my repo).

[glenvt18]

If so, it's OK. Small performance drop (about 3%) is expected on ARM. I sacrificed some performance in favor of safety and maintenance, but I have some ideas how to get it back:) I didn't notice any performance drop on x86 and AArch64 though.

Also tests on 32 bit Amlogic showed that the current LibreELEC compiler (6.2) produces code that is about 10% slower on ARM than the one generated by Linaro 5.4. I've also tried Linaro 6.2.1. It's only a little bit better and it doesn't generate ldm instructions which lead to bus errors. But, in practice, 132 Mbit/s you got is not bad at all.

[Ray-future]

I've tested this on my Odroid C2 with aarch64 and arm. Works for me. No more bus errors.

[lrusak]

@glenvt18 are you happy with this? do you want to update the git hash?

[glenvt18]

@lrusak Here you go. Just to point to my master branch. Though the changes are purely cosmetic.