[LLVMdev] LLVM LTO

[Hal Finkel]

Quick update: the previous patch only worked for static linking; this version should work for both static and dynamic linking.

I'm not going to send any more updated patches to this list, but please feel free to e-mail me off-list, and I'll be happy to share any updates I have at any point in the future.

 -Hal

----- Original Message -----
> Rafael, Rui,
> 
> This is obviously an old thread, but in case there is interest, I've
> been able to get this to work (using the LLVM gold plugin with the
> ld.bfd linker). This requires some additional logic in the ld.bfd
> linker (and a small change to the bfd library). I've attached the
> patch (against binutils HEAD from 2013-09-17) in case anyone finds
> this useful. The core issue is that ld.bfd is currently setup to use
> the GCC LTO plugin, which produces its IR in an ELF container, and
> we don't. As a result, ld.bfd needs to ask the plugin if it would
> like to claim files of unknown format (in addition to querying for
> recognized object files).
> 
>  -Hal
> 
> P.S. For the record, I'm certainly not a binutils expert, this just
> seems to work for me.
> 
> ----- Original Message -----
> > On 1 August 2012 23:00, Sun, Rui <rui.sun at intel.com> wrote:
> > > Hi,
> > >
> > >
> > >
> > > I am trying to use LLVM LTO. I read
> > > http://llvm.org/docs/GoldPlugin.html and
> > > have some questions. Could anyone help?
> > >
> > >
> > >
> > > 1.       Can LLVMgold.so work with BFD LD instead of gold? In the
> > > description of changes in binutils 2.20, “* The plugin target has
> > > been added
> > > to bfd. It can load the same shared objects
> > >
> > > used by gold and uses them to provide basic support for new file
> > > formats.”.
> > > Does this mean BFD LD after 2.20 can support LLVMgold.so?  Ld
> > > version on my
> > > system is:
> > >
> > > GNU ld (GNU Binutils for Ubuntu) 2.21.53.20110810
> > >
> > 
> > In theory it can, but I think it is completely untested.  I think
> > that, as with gold, you have to build it with --enable-plugins.
> > 
> > >
> > > 2.       Gold only supports ELF. If BFD LD can support LLVMgold,
> > > can LTO be
> > > applied to COFF objects after recompiling the binutils with
> > > target==x86_64-pc-pe?
> > 
> > Double untested, but I guess it could be made to work :-)
> > 
> > >
> > > Thanks!
> > >
> > > Rui
> > >
> > >
> > 
> > Cheers,
> > Rafael
> > 
> > _______________________________________________
> > LLVM Developers mailing list
> > LLVMdev at cs.uiuc.edu         http://llvm.cs.uiuc.edu
> > http://lists.cs.uiuc.edu/mailman/listinfo/llvmdev
> > 
> 
> --
> Hal Finkel
> Assistant Computational Scientist
> Leadership Computing Facility
> Argonne National Laboratory

-- 
Hal Finkel
Assistant Computational Scientist
Leadership Computing Facility
Argonne National Laboratory
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