It's interesting, in as much as there's been a constant bickering around whether the GPL vs Apache license for GCC and llvm means anything; to date, there general view has been that there's no evidence of anyone using LLVM to build compilers with closed extensions that are not released to the community; this is perhaps the first case of that.
Is there any evidence that Apple has an LLVM compiler with these extensions, versus using asm blocks within the Accelerate library source?
There's certainly prior cases of Apple shipping branches of LLVM (most notably adding arm64 support, which took about half a year to merge in upstream), but the mere existence of these instructions is little evidence of any branch?
No idea what the story is with AMX instructions, but Apple has been shipping an arm64e compiler for quite a while with changes that have not been upstreamed.
