"ld -r" on mixed IR/non-IR objects (

[H.J. Lu]

On Tue, Dec 7, 2010 at 3:57 PM, Andrew Pinski <pinskia@gmail.com> wrote:
> On Tue, Dec 7, 2010 at 3:53 PM, H.J. Lu <hjl.tools@gmail.com> wrote:
>> On Tue, Dec 7, 2010 at 3:15 PM, Cary Coutant <ccoutant@google.com> wrote:
>>>> Here is my proposal.  Any comments?
>>>
>>> We talked about ld -r a while back during the WHOPR project, and the
>>> two ways that the linker could work: (1) combine all the .o files and
>>> use the plugin to run LTRANS on the IR files, producing a pure,
>>> optimized, object file; and (2) combine the non-IR object files as ld
>>> -r normally would, and combine that result somehow with the IR from
>>> the other files, for later optimization. If I remember correctly,
>>> there was support for both modes of operation. The first mode is
>>> easily handled with the current design (untested as far as I know --
>>> there are probably bugs, and I'm not sure if we get the symbol
>>> visibility correct in those cases).
>>
>> We considered it.  The problem is LTO performs the best when
>> generating the final executable/DSO.  That is we want the full IR in the
>> output of "ld -r".
>
> What happens when ld -r is the final link?  Think loadable linux
> kernel modules and some other stuff that abuse elf relocatable
> objects?
>

"ld -plugin ... -r" will be treated as final link.


-- 
H.J.