This is the first I have heard of Apple doing this, and I feel like, in my position, I would have heard of this... I have just spent some time searching around myself trying to find any such reference and the closest I could find was the opposite: an article from Electrical Engineering Journal that said that Apple could have, but stated they didn't need to and pretty strongly implied they didn't, even going so far as to claim that they couldn't in any drastic way due redirections "even Apple" has on ARM licensees.
Can you provide some more information on this? I would love to be able to hit them on this, as this would actually be really upsetting to a lot of people I know who work on toolchains.
The rumor I've heard is that Apple is keeping their custom extensions to the ISA undocumented in deference to ARM's desire not to have the instruction set just completely fragment into a bunch of mutually incompatible company-specific dialects.
It's worth noting that the article you link predates the public release of the M1 by a good 10 months. Given how secretive Apple tends to be about these sorts of things, one can only assume that it was based almost entirely on rumor and conjecture.
Undocumented or not, they would be hard to hide: I would think you could scan through MacOS binaries and find them, if they exist. (I guess it's still possible they exist even if you don't find them, maybe unused or only produced by JITs, but that doesn't sound very useful.)
Yup. If you follow the links from that article, you'll get to the site of the person who found and documented them. It doesn't look like it took too much effort.
But it's not really about trying to prevent anyone from discovering that these opcodes exist. It's about trying to discourage their widespread use. If it's undocumented, then they don't have to support it, and anyone who's expecting support knows to steer clear. That gives them more freedom to change the behavior of this coprocessor in future iterations of the chip. And people can still get at them, because Apple uses them in system libraries such as the OS X implementation of BLAS.
Every ARM licensee does this though; they license the core designs from ARM and add features (including additional instructions) around it to package into an SOC. It’s just that Apple has the scale to design their own SOCs instead of buying one from Qualcomm or Samsung.
Which most - there is most as in number of cores shipped, and most as in number of organizations who have a license.
The second I have no doubt you are correct - I know of several organizations that have licensed ARM just to ensure they have a long term plan to get more without the CPU going obsolete again (one company has spent billions porting software that was perfectly working on a 16 bit CPUs that went obsolete - there was plenty of CPU for any foreseeable feature, but no ability to get more). These want something standard - they are kind of hoping that they can combine a production run with someone else in 10 years when they need more supply and thus save money on setup fees.
The first is a lot harder. The big players ship a lot of CPUs, and they the volumes to make some customization for their use case worth it. However I don't know how to get real numbers.
