[llvm-dev] Your help needed: List of LLVM Open Projects 2017

[Sean Silva via llvm-dev]

On Mon, Jan 16, 2017 at 1:25 PM, Davide Italiano <davide at freebsd.org> wrote:

> On Mon, Jan 16, 2017 at 12:31 PM, Sean Silva via llvm-dev
> <llvm-dev at lists.llvm.org> wrote:
> > Do we have any open projects on LLD?
> >
> > I know we usually try to avoid any big "projects" and mainly add/fix
> things
> > in response to user needs, but just wondering if somebody has any ideas.
> >
>
> I'm not particularly active in lld anymore, but the last big item I'd
> like to see implemented is Pettis-Hansen layout.
> http://perso.ensta-paristech.fr/~bmonsuez/Cours/B6-4/Articles/papers15.pdf
> (mainly because it improves performances of the final executable).
> GCC/gold have an implementation of the algorithm that can be used as
> base. I'll expand if anybody is interested.
> Side note: I'd like to propose a couple of llvm projects as well, I'll
> sit down later today and write them.
>


For FullLTO it is conceptually pretty easy to get profile data we need for
this, but I'm not sure about the ThinLTO case.

Teresa, Mehdi,

Are there any plans (or things already working!) for getting profile data
from ThinLTO in a format that the linker can use for code layout? I assume
that profile data is being used already to guide importing, so it may just
be a matter of siphoning that off.

Or maybe that layout code should be inside LLVM; maybe part of the general
LTO interface? It looks like the current gcc plugin calls back into gcc for
the actual layout algorithm itself (function call
find_pettis_hansen_function_layout) rather than the reordering logic living
in the linker:
https://android.googlesource.com/toolchain/gcc/+/3f73d6ef90458b45bbbb33ef4c2b174d4662a22d/gcc-4.6/function_reordering_plugin/function_reordering_plugin.c

-- Sean Silva


>
> --
> Davide
>
> "There are no solved problems; there are only problems that are more
> or less solved" -- Henri Poincare
>
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