Earlier quoted context omitted.
What is the measurable benefit to implementing 128b SVE2? Like, ARM has CPUs that implement that, and it's not even disabled on some chips. So there must be benchmarks somewhere showing how worthwhile it is. And implementing 256b SVE has different issues depending on how you do it. 4x256b vector ALUs are more power hungry than generally useful. 2x256b is only beneficial over 4x128b if you're limited by decode width,…
I'd say that the theoretical ability to gang units together would be appealing. If you have four 128-bit packed SIMD, you must execute 4 different instructions at once or the others go to waste. With SVE, you could (in theory) use all 4 as a single, very wide vector for common operations if there weren't a lot of instructions competing for execution ports. You could even dynamically allocate them based on expected ve…
Re: Apple's M4 has reportedly adopted the ARMv9 architecture
#201You can't do 2048 bits of addition in one SVE instruction; not portably, at least (and definitely not on any existing hardware). While the maximum SVE register size is 2048 bits, the minimum is 128 bits, and the hardware chooses the supported register size, not the programmer. For portable SVE, your code needs to work for all of those widths, not just the smallest or largest. (of related note is RISC-V RVV, which allows you to group up to 8 registers together, allowing a minimum portable operation width of 128×8 = 1024 bits in a single instruction (and up to 65536×8 = 64KB for hypothetical crazy hardware with max VLEN), but SVE/SVE2 don't have any equivalent)