aarch64 feature modifiers

[Christer Solskogen]

On 21.02.2022 12:35, Richard Sandiford via Gcc-help wrote:
> Christer Solskogen via Gcc-help <gcc-help@gcc.gnu.org> writes:
>> On https://gcc.gnu.org/onlinedocs/gcc/AArch64-Options.html there's a
>> list of feature modifiers to -march and -mcpu. Is there a way to check
>> or detect what features are available on a particular CPU?
> 
> If you want to compile for a specific CPU then it's better to use
> -mcpu=<that-cpu> with no feature modifiers, and leave out -march.
> GCC will then make full use of the available features.
> E.g. -mcpu=neoverse-n1 (on its own) will enable all features
> available on Neoverse N1 and optimise code for Neoverse N1.
> 
> If you're just curious which features a given CPU implements,
> you can find that out by compiling a dummy file with -mcpu.  E.g.:
> 
>    echo | gcc -mcpu=neoverse-n1 -xc - -o - -S | grep '\.arch'
> 
> will print out:
> 
>          .arch armv8.2-a+crc+fp16+rcpc+dotprod+profile
> 
>

I see. Thank you.
Does that mean that the cortex-a72 doesn't really support the +crypto or 
+simd? Or does that depend on what is built?

-- 
chs