Re: [Qemu-devel] [RFC PATCH v2 1/2] utils: Add helper to read arm MIDR_EL1 register

[Peter Maydell]

On 18 August 2016 at 15:46, Richard Henderson <address@hidden> wrote:
> On 08/18/2016 07:14 AM, Peter Maydell wrote:
>> While we're on the subject, can somebody explain to me why we
>> use ifuncs at all? I couldn't work out why it would be better than
>> just using a straightforward function pointer -- when I tried single
>> stepping through things the ifunc approach still seemed to indirect
>> through some table or other so it wasn't actually resolving to
>> a direct function call anyway.

> No reason, I suppose.
>
> It's particularly helpful for libraries, where we don't really want the
> overhead of the initialization when it's not used.

Ah, I see.

> But (1) we don't have many of these and (2) we really don't care *that* much
> about startup time.
>
> So a simple function pointer initialized by a constructor has the same
> effect.

That seems like it would be a worthwhile change since
(a) I think it's easier to understand than ifunc magic
(b) it means we don't unnecessarily restrict ourselves to a libc
with ifunc support (musl libc doesn't do ifuncs, for instance)

thanks
-- PMM