Re: Internal unwinding clobbers non-volatile registers.
- From: Mike Pall <mikelj-2105@xxxxxxx>
- To: luajit@xxxxxxxxxxxxx
- Date: Mon, 31 May 2021 11:56:44 +0200
Can Boluk wrote:
Does this behave as it should for non-MS x64 ABIs, System V for instance?
[...] ymm8-ymm15 [...]
Yes, because most registers are not saved in this ABI. And ymms
follow suit with xmms.
[In other words: the MS ABI is problematic. It's the root cause
for most of the trouble when mixing AVX and SSE code, e.g. the
annoying VZEROUPPER instruction.]
I'm using LuaJIT in a custom baremetal Ring0 environment so I'm by no means
restricted to MS ABI, it's mainly that I cannot use external unwinding
since I don't have unwind tables [...]
Well, you could certainly generate those. I think it's more an
issue with supplying a working unwinder that handles them.
[
The actual problem you'll eventually run into on such a platform,
is that only external unwinding is able to catch on-trace errors.
So far, this was mostly about catching out-of-memory errors, which
are fatal in most environments, anyway. But some future APIs, e.g.
the fast serializer, which is part of the new string buffer library,
will often be combined with pcall and need on-trace error handling.
]
--Mike
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