[LLVMdev] Unwind behaviour in Clang/LLVM

[Renato Golin]

On 7 February 2014 09:35, Renato Golin <renato.golin at linaro.org> wrote:

> Do we have such logic in Clang at the moment?
>

Let me answer my own question. Right now, both -funwind-tables and
-fno-unwind-tables only enable the -muniwind-tables for -cc1, and either
lack or presence of that flag in -cc1 has the same behaviour on C++ code:
they both generate .eh_frame sections.

The only behaviour I found is that -munwind-tables will add uwtable to
functions, which had no effect on x86_64. Is that because x86_64 mandates
unwind tables?

If the semantics is that uwtable turns on tables on targets that don't
require it (SjLj), but not that it turns off if missing on targets that
mandate it, I can't use it to disable them on ARM. To be honest, recently,
I'm not even sure I need, or want to disable.

With Keith's patch to generate Dwarf unwind, the -arm-disable-ehabi flag
could possibly be removed clean, and we can go directly to step 2.

Keith, Reid, are you happy with always generating unwind tables on ARM
regardless?

cheers,
--renato
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