Comment by adrian_b
2 days ago
NEON is a name that should never be used again, because it is extremely ambiguous. Whenever someone speaks about Arm NEON it is impossible to guess what instruction set is meant.
The 32-bit Arm architectures have used several kinds of floating-point units, with very distinct capabilities, so when compiling a program for 32-bit Arm CPUs you must always provide a specific FPU selecting option to the C/C++ compiler, the one correct for the target CPU, otherwise the performance will be suboptimal. (an example of how such a compiler option looks like: "-mfpu=fpv5-d16")
Only the 64-bit Aarch64 has cleaned up this mess, so for Armv8-A there is a well defined FPU instruction set, supported by all CPUs.
The Armv9.0-A and Armv9.2-A CPUs continue to support the original 64-bit FP instruction set, but they add SVE and SVE2.
The Armv9.3-A CPUs, launched last autumn, continue to support the original 64-bit FP instruction set + SVE + SVE2, but they add SME and SME2.
The Apple CPUs implement the original 64-bit FP instruction set but they do not implement SVE/SVE2 (except in a non-performant "streaming" mode), but in the past they had a non-documented AMX extension and now they have SME.
For a while it looked like ARM was trying to call the ARMv8 vector instruction set ASIMD instead of NEON, but they seem to have thrown in the towel as the ARM Intrinsics Guide simply refers to Neon.