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Re: "ld -r" on mixed IR/non-IR objects (
On Wed, Dec 8, 2010 at 1:19 AM, Andi Kleen <andi@firstfloor.org> wrote:
>> On 12/07/2010 04:20 PM, Andi Kleen wrote:
>>>
>>> The only problem left is mixing of lto and non lto objects. this right
>>> now is not handled. IMHO still the best way to handle it is to use
>>> slim lto and then simply separate link the "left overs" after deleting
>>> the LTO objects. This can be actually done with objcopy (with some
>>> limitations), doesn't even need linker support.
I agree that FAT lto objects are not necessary to make the everything
work and the integration of LTO with existing build environment
'transparent' --- there is compiler out in the world that does just
that -- produces IL only objects (wrapped in elf format); works with
archives with mixed objects; works with ld -r with mixed objects;
builds unix kernel successfully with LTO ...
David
>>>
>>
>> Quite possibly a better way to deal with that is to provide a mechanism
>> for encapsulating arbitrary binary code objects inside the LTO IR.
>
> Then you would need to teach your assembler and everything
> else that may generate ELF objects to generate this magic object. But why
> not just ELF directly? that is what it is after all.
>
> To be honest I don't really see the point of all this complexity you
> guys are proposing just to save fat LTO. Fat LTO is always a bad idea
> because it's slow and ?does lots of redundant work. If LTO is to become
> a more wide spread mode it has to go simply because of the poor
> performance.
>
> With slim LTO passthrough is ?very straight-forward: simple pass
> through every section that is not LTO and generate code for the LTO
> sections. No new magic sections needed at all.
>
> -Andi
>
>