It has a fixed polynomial, so not really that useful for anything but AES
The only case where I've had use of GF(2^8) inverses is in FEC algorithms (Forney's algorithm) and then you need some kind of weird polynomial. But all of those needs are rarely in the hot-path, and the FEC algo's are way outdated
I think the AFFINE and AFFINEINV instructions are specifically for FEC and maybe compression algorithms. I also think they smell like something requested by one of the big customers of Intel (e.g. the government).
Hmm of course erasure codes would always need to solve these problems. Not sure what modern applications need that in the X86 world
I really think it's only AES since thats the only place I've seen that polynomial used. But of course maybe there's an obscure tape backup FEC algo used somewhere in datacenters?
Comments
What about GF2P8AFFINEINVQB?
It has a fixed polynomial, so not really that useful for anything but AES
The only case where I've had use of GF(2^8) inverses is in FEC algorithms (Forney's algorithm) and then you need some kind of weird polynomial. But all of those needs are rarely in the hot-path, and the FEC algo's are way outdated
I think the AFFINE and AFFINEINV instructions are specifically for FEC and maybe compression algorithms. I also think they smell like something requested by one of the big customers of Intel (e.g. the government).
Hmm of course erasure codes would always need to solve these problems. Not sure what modern applications need that in the X86 world
I really think it's only AES since thats the only place I've seen that polynomial used. But of course maybe there's an obscure tape backup FEC algo used somewhere in datacenters?
The forward affine matrix is useful for all sorts of bit manipulation, e.g. something as simple as a bit reversal.
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