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Apple's M4 has reportedly adopted the ARMv9 architecture

wccftech.com

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Re: Apple's M4 has reportedly adopted the ARMv9 architecture

#221

Post by anticensor »

hajile wrote: post #141
skavi wrote: post #138

Earlier quoted context omitted.

Does anyone have insight into why arm CPU vendors seem so hesitant about implementing SVE2? ~They seem~ *Apple seems to have no issue with SSVE2 or SME. Edit: Only Apple has implemented SSVE and SME I think.

SVE2 is an extension on top of SVE which some stuff already implements. The issue is more likely to be the politics of moving to ARMv9 than anything else. As to SVE though, I'd guess variable execution time makes the implementation require a bit of work. Normally, multi-cycle tasks have a fixed number. Your scheduler knows that MUL takes N cycles and plans accordingly. SVE seems like it should require N-M cycles depe…

Variable execution time instructions can always be divided into smaller fixed execution time microinstructions.

Re: Apple's M4 has reportedly adopted the ARMv9 architecture

#222

Post by lynguist »

mft_ wrote: post #44
Aaargh20318 wrote: post #18

The most incredible thing about the new iPads is that even with the crazy fast M4 chip MS Teams manages to crawl to a halt. Clearly it takes all the engineering skills of the largest and most valuable software company in the world to make text entry go at about 1 fps on a chip as powerful as the M4.

LOL, you wanna try it on my ~2 generations old Core i5 corporate laptop. Sometimes, the first steps of drawing the calendar view are roughly the same speed as me drawing it in Paint. Maybe someone should normalise giving developers crappy laptops to develop on. (Has anyone done a deep dive into Teams to explain what on earth is going on? I mean, if VSCode can be fast despite its underlying architecture, surely someth…

This actually I don’t get and don’t stand behind.

Would you give a professional smith a low quality hammer? Would you give a chef a blunt knife?

Why do corporations give out garbage hardware to their smiths and chefs (+ enforce their use via policy) ?

Re: Apple's M4 has reportedly adopted the ARMv9 architecture

#223

Post by TiredOfLife »

saagarjha wrote: post #179

I do find it amusing that journalists never go beyond Twitter for discussion on this because this was all being confirmed on Mastodon days before any of the posts in the article

According to https://news.ycombinator.com/item?id=40465451 they have not switched to armv9. So I am curious what they were confirming?

Re: Apple's M4 has reportedly adopted the ARMv9 architecture

#226

Post by saagarjha »

TiredOfLife wrote: post #223
saagarjha wrote: post #179

I do find it amusing that journalists never go beyond Twitter for discussion on this because this was all being confirmed on Mastodon days before any of the posts in the article

According to https://news.ycombinator.com/item?id=40465451 they have not switched to armv9. So I am curious what they were confirming?

SME and streaming SVE. In fact I was going to include “…and nobody seems to have good evidence of ARMv9 support” but I figured my comment was enough as it was ;)

Re: Apple's M4 has reportedly adopted the ARMv9 architecture

#227

Post by joshstrange »

zarathustreal wrote: post #209
saagarjha wrote: post #179

I do find it amusing that journalists never go beyond Twitter for discussion on this because this was all being confirmed on Mastodon days before any of the posts in the article

Thing is, normal people don’t really like interacting with the kind of person that would have jumped over to Mastodon. Zeal is insufferable most of the time.

I’m fairly certain that staying on (or joining) Twitter shows just about the same amount of “zeal” as leaving for Mastodon/BlueSky/Threads. Or put another way, I find people on Twitter to be insufferable.

It’s not a secret that a large portion of actually technical people (not tech influencers) left Twitter for Mastodon. So the people on Twitter may be more polished turds but are turds nonetheless.

Full disclosure: I still use my Twitter for customer support because that’s all it’s good for at this point IMHO. I also don’t regularly read mastodon but it’s where the people I care about are and when I post (rarely) that’s where I do it.

Re: Apple's M4 has reportedly adopted the ARMv9 architecture

#228

Post by joshstrange »

dumbo-octopus wrote: post #168
rbanffy wrote: post #165

Earlier quoted context omitted.

And, in modern desktop software, code is a tiny bit of the total size of the application - visual elements tend to occupy a lot more space than code.

In games, perhaps. In basically nothing else though. And I have 0 games on my M1, yet my apps folder is 23 GB. Docker, Edge, and SketchUp all 2+ GB, despite not having almost any UI to speak of. (Edit to remove iMovie from the list, as it has GB's of "Transitions" and "Titles" that I really should just delete)

There are cases where the app icon is larger than the compiled code in some apps and if you include a couple images for things like “here is how you give my app access to record the screen” that can also account for a large part of your app bundle.

Yes, game assets really take it to another level but it’s been my experience that even apps without a lot of UI still have their images making up a lot of the app bundle size.

Re: Apple's M4 has reportedly adopted the ARMv9 architecture

#229

Post by janwas »

brigade wrote: post #152
skavi wrote: post #149

Earlier quoted context omitted.

Masked instructions primarily. But apart from that it’s just a more complete ISA vs NEON. More comparable to AVX512/AVX10. > 2x256b is only beneficial over 4x128b if you're limited by decode width This is only true if we ignore more complex instructions and focus on things like adding two vectors.

What is the percentage gain of using masked instructions on any benchmark/task of your choice? It can be negative on weird kernels that do lots of vector cmp since even ARM decided the cost of more than one write port in the predicate register file wasn't worth it, or if the masking adds lots of unnecessary and possibly false dependencies on the destination registers. > This is only true if we ignore more complex ins…

It's great you bring up cmp, helps to understand why 4x128 is not necessarily as good as 1x512. Quicksort, hardly a 'weird kernel', does comparisons followed by compaction. Because comparisons return a predicate, which have only a single write port, we can only do 128 bits of comparisons per cycle. Ouch.

However, masking can still help our VQSort [1], for example when writing the rightmost partition right to left without stomping on subsequent elements, or in a sorting network, only updating every second element.

[1] https://github.com/google/highway/tree/master/hwy/contrib/so...

Re: Apple's M4 has reportedly adopted the ARMv9 architecture

#230

Post by janwas »

brigade wrote: post #196
skavi wrote: post #181

Earlier quoted context omitted.

I think it's somewhat unfair to ask for real world examples when there really aren't many people writing optimized SVE code right now. Probably because there are hardly any devices with the extension. I think the transition from AVX2 to AVX512 is comparable in that it provided not only larger vectors, but also a much nicer ISA. There were certainly a few projects that benefited significantly from that move. simdjson…

CPUs with SVE have been generally available for two years now. SME and AVX-512 got benchmarks written showing them off before the CPUs were even available. Seems fair to me. simdjson specifically benefitted from Intel's hardware decision to implement a 512b permute from 2x 512b registers with a throughput of 1/cycle. That's area-expensive, which is (probably) why ARM has historically skimped on tbl performance, only…

Fair point about movprfx, I understand they were short on encoding space. This can be mitigated by using *_x versions of intrinsics where masks are not used.

The sizeless headache is anyway there if you want to support RISC-V V, which we do.

One other data point in favor of SVE: its backend in Highway is only 6KLOC vs NEON's 10K, with a similar ratio of #if (indicating less fragmentation, more orthogonal).

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