Re: [7/9][AArch64, libgcc] Let AArch64 use customized unwinder file

[Jiong Wang <jiong.wang@foss.arm.com>]

On 11/11/16 22:12, Joseph Myers wrote:
> On Fri, 11 Nov 2016, Jiong Wang wrote:
>
>> There are two ways of introducing these AArch64 support:
>>    * Introducing a few target macros so we can customize functions like
>>      uw_init_context, uw_install_context etc.
>>    * Use target private unwind-dw2 implementation, i.e duplicate the generic
>>      unwind-dw2.c into target config directory and use it instead of generic
>> one.
>>      This is current used by IA64 and CR16 is using.
>>
>> I am not sure which approach is the convention in libgcc, Ian, any comments on
>> this?
> Although as you note duplication has been used before, I think it should
> be strongly discouraged; duplicated files are unlikely to be kept up to
> date with relevant changes to the main file.
>
>
> Hi Joseph,

   The changes AArch64 needs to do on top of the generic unwind-dw2.c is at:

      https://gcc.gnu.org/ml/gcc-patches/2016-11/msg01167.html

   If I don't duplicate unwind-dw2.c, then I need to guard those changes with
something like __aarch64__ or introduce several target macros.  It looks to me
only the hunk that supports AArch64 DWARF operations worth a target macro,
something like MD_DW_OP_HANDLER, for the other changes they are quite scattered,
for example the field extension on "struct _Unwind_Context" and the relax of
assertion on uw_install_context_1.

   Any comments on this?

   Thanks.

Regards,
Jiong