[haiku-development] Re: Changing ByteOrder.h
- From: Jessica Hamilton <jessica.l.hamilton@xxxxxxxxx>
- To: haiku-development@xxxxxxxxxxxxx
- Date: Thu, 8 May 2014 19:45:19 +1200
>> In ticket #10800, initially I thought problems with the byteswap
>> implementations was related to calling conventions, however, digging
>> deeper and after some clarification by tqh, it's obviously not the
>> case.
>>
>> It was also suggested to use GCC builtins to replace the existing
>> byteswap functions, and I have the beginnings of a patch:
>>
>> https://dev.haiku-os.org/attachment/ticket/10800/0001-Replace-arch-dependent-integer-byteswap-routines-wit.patch
>>
>> Is this the right place to do this?
>
>
> Yep, looks good. I'd also replace the implementation of the __swap_int*() by
> a call the the respective built-in (i.e. replace the per-arch assembly
> implementation by a generic one). We can eventually even drop the non-gcc 2
> ones.
>
> I guess the float and double versions can be mapped to the int versions as
> well with some casting.
>
>
>> Is it sufficient to assume this
>> will be okay on all our platforms, or do we still want the builtins
>> abstracted? If so, can that be done without losing the ability to
>
>> inline them?
>
> I don't think we need an abstraction. Only for BeOS binary compatibility we
> the function definitions. At least according to the gcc 4.8.2 documentation
> [1], the built-ins are available on all architectures. At a first glance,
> gcc 2.95.3 doesn't seem to provide them, though [2].
Yes, I tried building gcc2h image, and it failed with undefined
references to the builtins. So in terms of ABI, do the __swap_xyz()
functions only need to be preserved when compiling with gcc2? I.e.
other builds it will be inlined, and __swap_xyz() won't be part of the
ABI?
i.e. like in
https://dev.haiku-os.org/attachment/ticket/10800/0001-Use-GCC-builtins-for-byte-swapping.-Fixes-10800.patch
It would then also be safe to completely remove the external
definitions for the non-x86 architectures as well, correct?
Jessica
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