[PATCH] libc++abi: Don't push the unwind_exception to r12 in _gxx_personality_v0.

[Jonathan Roelofs]

On 5/29/14, 6:53 PM, Dana Jansens wrote:
> On Thu, May 29, 2014 at 8:27 PM, Jonathan Roelofs <jonathan at codesourcery.com
> <mailto:jonathan at codesourcery.com>> wrote:
>
>
>
>     On 5/28/14, 9:08 AM, Dana Jansens wrote:
>
>         -    // Copy the address of _Unwind_Control_Block to r12 so that
>         _Unwind___GetLangauageSpecificData()
>         -    // and _Unwind_GetRegionStart() can return correct address.
>         -    _Unwind_SetGR(context, REG_UCB,
>         reinterpret_cast<uint32_t>(__unwind_exception));
>
>
> Hey! Thanks for the pointers.
>
>     libgcc does in fact need us to pass the UCB in r12. See:
>     gcc-trunk-4.8/libgcc/arm/pr-__support.c.
>
>
> It looks like we only need to call these methods on !ARM EHABI from our own
> libc++abi personality function. So I'm going to move them into that #if, along
> with the register setting, and avoided calling either method on ARM EHABI.
>
>
>     We should probably keep this, but put it under LIBCXXABI_USE_GLIBC for when
>     using libgcc's unwinder with libc++abi, as our unwinder implementation
>     doesn't do it that way.
>
>
> I think our local LIBCXXABI_USE_GLIBC is a mis-nomer and it's going to go away.
> We probably want to pull our unwind library out of libc++abi so that we can drop
> in GCC's if desired. It seems like our libc++abi shouldn't necessarily know what
> unwinder it will be using at compile time, but should just work with whichever
> gets used?
Good point.  Given that, maybe we ought to keep it in there.
>
> However, for now we aren't passing the needed data to the personality function
> on EHABI yet upstream so we need to keep calling these _Unwind methods there
> still also. So I'm going to hold off on this patch until we upstream some other
> dependent pieces for this to make more sense.
SGTM
>
> Thanks!
> - Dana

-- 
Jon Roelofs
jonathan at codesourcery.com
CodeSourcery / Mentor Embedded