AArch64 definitely has a much more comprehensive baseline than x86-64, but there are some optional extensions that are situationally impactful, including the Crypto extension and some of the newer accumulation / dot product instructions. And unlike Intel, ARM has no portable equivalent to CPUID for querying feature flags and is terrible at documenting which intrinsics require specific FEAT_* flags.
The ARM-based CPU manufacturers make this worse by posting almost no low-level documentation for their CPUs. For basically any mainstream x86 CPU, it's trivial to find documentation listing what ISA level it supports and general execution widths and latencies for common operations. For the majority of ARM CPUs, there's absolutely nothing. ARM only has optimization guides for selected Cortex cores, and NVIDIA published info for their Olympus core. But execution details had to be reverse engineered for Apple M1, and there is nothing for Oryon. This is especially bad for in-order cores, which unfortunately is still relevant because new CPUs are still being shipped with in-order efficiency cores.
I really hope this is my last x86-64 CPU, Intel has become an incompetent steward. The "killer feature" for AVX-2(56) at the time of original release was basically lag/jitter-free video playback. IMO, 512 should have never been released for desktop CPUs and restricted to servers. One day I will to switch to a mainstream Neoverse dev box running linux. I also target Cortex-M in rust, so it's got a lot of the typical issues related to missing docs (e.g. bringup of non-heterogenous cores, meaning that M3/M4 still can't be used in a big.little chip)
Neither is AVX or AVX2. AVX512 isn't avaiable on some of the latest intel CPUs is purely because intel can't say goodbye to Skylake for some reason.
AVX2 is much more prevalent than AVX-512 and thus tenable to require. RHEL is switching to x86-64-v3 baseline, for instance, which requires AVX2. AVX-512, on the other hand, has been moving backwards since Intel has not shipped any consumer-level CPUs with it for years now. The Steam Hardware Survey has AVX2 at 95.4% while AVX512F is still far behind at 23.9%.
So? AVX-512 shouldn't exist because it can't be retroactively enabled on older hardware? or because Intel can't say goodbye to Skylake? I don't understand the logic.
> AVX-512, on the other hand, has been moving backwards since Intel has not shipped any consumer-level CPUs with it for years now.
Good thing Intel hasn't shipped a viable consumer-level CPU in years either. What should never have happened is Intel removing AVX-512.
> Steam Hardware Survey
While it's a good source, it's not a definitive source. Four out of five amd64 machines at my place support AVX-512F, but none of them participate in that survey. And the one machine that doesn't have it... I wish it did.
At one point, Intel integrated graphics were literally the most common individual GPU in the Steam Hardware Survey - Intel HD 4000 held the #1 spot until the GTX 970 overtook it in late 2015. Does that mean developers shouldn't have targeted discrete GPUs either, just because most survey participants didn't have the hardware they wanted to target?
ack_complete · · focus · HN ↗
The ARM-based CPU manufacturers make this worse by posting almost no low-level documentation for their CPUs. For basically any mainstream x86 CPU, it's trivial to find documentation listing what ISA level it supports and general execution widths and latencies for common operations. For the majority of ARM CPUs, there's absolutely nothing. ARM only has optimization guides for selected Cortex cores, and NVIDIA published info for their Olympus core. But execution details had to be reverse engineered for Apple M1, and there is nothing for Oryon. This is especially bad for in-order cores, which unfortunately is still relevant because new CPUs are still being shipped with in-order efficiency cores.
officialchicken · · focus · HN ↗
Tuna-Fish · · focus · HN ↗
nextaccountic · · focus · HN ↗
0x457 · · focus · HN ↗
ack_complete · · focus · HN ↗
0x457 · · focus · HN ↗
> AVX-512, on the other hand, has been moving backwards since Intel has not shipped any consumer-level CPUs with it for years now.
Good thing Intel hasn't shipped a viable consumer-level CPU in years either. What should never have happened is Intel removing AVX-512.
> Steam Hardware Survey
While it's a good source, it's not a definitive source. Four out of five amd64 machines at my place support AVX-512F, but none of them participate in that survey. And the one machine that doesn't have it... I wish it did.
At one point, Intel integrated graphics were literally the most common individual GPU in the Steam Hardware Survey - Intel HD 4000 held the #1 spot until the GTX 970 overtook it in late 2015. Does that mean developers shouldn't have targeted discrete GPUs either, just because most survey participants didn't have the hardware they wanted to target?
nextaccountic · · focus · HN ↗
If the issue were just older hardware, we could just wait out and let people upgrade a bit. But new hardware are shipping without AVX512 unfortunately