llvm dev - May 2020 - RFC] Shrink-wrapping improvement

Hi,

Sorry for bringing back such an old thread. I am interested in the latest status
of the shrink wrapping pass in LLVM. I have found some active work back in 2017
from Francis Visoiu Mistrih and Kit Barton from the following links. However, it
seems that all the work suddenly stops and the improvement for the existing
shrink wrapping did not make it into the trunk. Is this work abandoned?

https://lists.llvm.org/pipermail/llvm-dev/2017-August/116131.html
http://lists.llvm.org/pipermail/llvm-dev/2017-May/112687.html
https://reviews.llvm.org/D41765

Thanks,
Jimmy
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Hi Jimmy,
> On May 13, 2020, at 2:25 PM, Jimmy Zhongduo Lin via llvm-dev <llvm-dev
at lists.llvm.org> wrote:
> 
> Hi,
>  
> Sorry for bringing back such an old thread. I am interested in the latest
status of the shrink wrapping pass in LLVM. I have found some active work back
in 2017 from Francis Visoiu Mistrih and Kit Barton from the following links.
However, it seems that all the work suddenly stops and the improvement for the
existing shrink wrapping did not make it into the trunk. Is this work abandoned?
Thanks for bringing this back.

On my side, the last time I was working on this was more on the integration on
the Darwin platforms. Most of these improvements break a lot of assumptions that
lots of tools use (debuggers, profilers, crash reporters, unwinders, etc.). At
least for Darwin, the gains we can get from such tools is a lot higher than the
performance we get from improving shrink-wrapping. So first, we would need to
come up with a solution to support such code out there (for example, improving
the compact unwinding format), and then we can put more work into extending
shrink-wrapping.

Having said that, I can probably help with discussions and reviewing patches!

Hope that helps,

— 
Francis
>  
> https://lists.llvm.org/pipermail/llvm-dev/2017-August/116131.html
> http://lists.llvm.org/pipermail/llvm-dev/2017-May/112687.html
> https://reviews.llvm.org/D41765
>  
> Thanks,
> Jimmy
> _______________________________________________
> LLVM Developers mailing list
> llvm-dev at lists.llvm.org
> https://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev

Hi Francis,

Thanks for getting back to me. Could you please provide more details about the
problems you encounter with those tools and what improvements required to
improve compact unwinding format? Most of my experience is in the mid end, but
it is still surprising to me that an improved shrink wrap will break that many
tools, considering the fact that gcc has a good shrink wrapping pass and
shrink-wrap-separate pass.

Also, if possible, would you be able to share some performance numbers you get
back then by improving shrink-wrap?

Thanks,
Jimmy

-----Original Message-----
From: Francis Visoiu Mistrih [mailto:francisvm at yahoo.com] 
Sent: Thursday, May 14, 2020 7:30 PM
To: Jimmy Zhongduo Lin <jimmy.zhongduo.lin at huawei.com>
Cc: llvm-dev at lists.llvm.org
Subject: Re: [llvm-dev] RFC] Shrink-wrapping improvement

Hi Jimmy,
> On May 13, 2020, at 2:25 PM, Jimmy Zhongduo Lin via llvm-dev <llvm-dev
at lists.llvm.org> wrote:
> 
> Hi,
>  
> Sorry for bringing back such an old thread. I am interested in the latest
status of the shrink wrapping pass in LLVM. I have found some active work back
in 2017 from Francis Visoiu Mistrih and Kit Barton from the following links.
However, it seems that all the work suddenly stops and the improvement for the
existing shrink wrapping did not make it into the trunk. Is this work abandoned?
Thanks for bringing this back.

On my side, the last time I was working on this was more on the integration on
the Darwin platforms. Most of these improvements break a lot of assumptions that
lots of tools use (debuggers, profilers, crash reporters, unwinders, etc.). At
least for Darwin, the gains we can get from such tools is a lot higher than the
performance we get from improving shrink-wrapping. So first, we would need to
come up with a solution to support such code out there (for example, improving
the compact unwinding format), and then we can put more work into extending
shrink-wrapping.

Having said that, I can probably help with discussions and reviewing patches!

Hope that helps,

— 
Francis
>  
> https://lists.llvm.org/pipermail/llvm-dev/2017-August/116131.html
> http://lists.llvm.org/pipermail/llvm-dev/2017-May/112687.html
> https://reviews.llvm.org/D41765
>  
> Thanks,
> Jimmy
> _______________________________________________
> LLVM Developers mailing list
> llvm-dev at lists.llvm.org
> https://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev