llvm dev - Aug 2012 - [LLVMdev] LLVM LTO

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


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?

Thanks!
Rui

-------------- next part --------------
An HTML attachment was scrubbed...
URL:
<http://lists.llvm.org/pipermail/llvm-dev/attachments/20120802/3a7ded3c/attachment.html>

2012/8/2 Sun, Rui <rui.sun at intel.com>:
> 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?
FYI, the last time I attempted, I was not able to activate lto.
IIRC, I met some sorts of crashing.
Let's know if you could, thanks ;)

...Takumi

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

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
-------------- next part --------------
A non-text attachment was scrubbed...
Name: ldbfd-bin-plugin.patch
Type: text/x-patch
Size: 2121 bytes
Desc: not available
URL:
<http://lists.llvm.org/pipermail/llvm-dev/attachments/20131010/fc3217b5/attachment.bin>