Re: [PATCH] Report support for optional ARMv8.2 half-precision floating point extension

George Pee
2022-09-09T14:57:59Z

The details are here. I originally thought it was a compiler bug
because it first showed up after a toolchain update.

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=106763

Since FP16 is an optional extension, wouldn't it be beneficial to a
user who compiled some userspace float16 code using gcc
-mcpu=cortex-a55 which ran on a cortex-a55 with FP16 extensions but
SIGILL'd on a cortex-a55 w/o FP16?

On Fri, Sep 9, 2022 at 9:07 AM Catalin Marinas <catalin.marinas@arm.com> wrote:
>
> On Fri, Sep 09, 2022 at 08:34:26AM -0500, George Pee wrote:
> > Adding the hwcap was part of the diagnosis process-- I added it just
> > to make sure that the cpu in question supported the optional
> > extension.
> > It seems like it could be useful to be able to check for support in
> > /proc/cpuinfo.
>
> Ah, I wasn't aware that the feature doesn't work on arm32. I don't think
> it makes sense to expose a hwcap bit to user in this case.
>
> --
> Catalin