5 ms·
When I was being taught assembly at Intel, one of the graybeards told me that the greatest waste of an integer was to use it for a "bare" add, when it was a per
by thechao 1y ago
When I was being taught assembly at Intel, one of the graybeards told me that the greatest waste of an integer was to use it for a "bare" add, when it was a perfectly acceptable 64-wide vector AND. To belabor the the point: he used ADD for the "unusual set of XORs, ANDs, and other funky operations it provided across lanes". Odd dude.
- uticus 1y ago> ...it was a perfectly acceptable 64-wide vector AND. sounds like "don't try to out-optimize the compiler."
- thechao 1y agoIn 2025, for sure. In 2009 ... maybe? Of course, he had become set in his ways in the 80s and 90s.
- dragontamer 1y agoReverse engineering the mindset.... In the 90s, a cryptography paper was published that more quickly brute forced DES (standard encryption algorithm back then) using SIMD across 64-bit registers on a DEC Alpha. There is also the 80s Connection Machine which was a 1-bit SIMD x 4096-lane supercomputer. --------------- It sounds like this guy read a few 80s or 90s papers and then got stuck in that unusual style of programming. But there were famous programs back then that worked off of 1-bit SIMD x 64 lanes or x4096 lanes. By the 00s, computers have already moved on to new patterns (and this obscure methodology was never mainstream). Still, I can imagine that if a student read a specific set of papers in those decades... This kind of mindset would get stuck.
- formerly_proven 1y agoThat's bit-slicing (not the hardware technique).