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Re: RFA: Use _Unwind_Ptr (Was: Re: RFC / RFA: dwarf2 unwinding for targets with call-part-clobbered registers)
- From: Richard Henderson <rth at redhat dot com>
- To: Joern Rennecke <joern dot rennecke at superh dot com>
- Cc: Jim Wilson <wilson at tuliptree dot org>, gcc at gcc dot gnu dot org, gcc-patches at gcc dot gnu dot org
- Date: Thu, 10 Jul 2003 11:13:46 -0700
- Subject: Re: RFA: Use _Unwind_Ptr (Was: Re: RFC / RFA: dwarf2 unwinding for targets with call-part-clobbered registers)
- References: <20030710172431.GE1411@redhat.com> <200307101753.h6AHriO10740@linsvr1.uk.superh.com>
On Thu, Jul 10, 2003 at 06:53:44PM +0100, Joern Rennecke wrote:
> > Hum. I'm not thrilled. And I think it may miss out on external
> > users of _Unwind_GetGR etc.
>
> I can't find any evidence of relevant external users.
Perhaps not _Unwind_GetGR in gcc directly, but it is an ABI
specified interface. We do use _Unwind_SetGR in gcc source.
> I think you need a cast here to avoid a warning.
Not for extension of an integer, surely.
> That would appear to give the right result - and even with more
> functionality consistently available.
> However, won't that kill unwinding performance?
I wouldn't expect so. That was one of the reasons that I
checked only specific sizeof's, and didn't use read_[248],
which would fall back to unaligned loads (which fall back
to byte-by-byte loads).
I would expect the difference on x86 to be
cmpl $4, mem
jne to_abort
which should be non-measurable.
r~