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

["H.J. Lu" <hjl dot tools at gmail dot com>]

On Thu, Dec 9, 2010 at 8:55 PM, H.J. Lu <hjl.tools@gmail.com> wrote:
> On Thu, Dec 9, 2010 at 6:29 PM, H.J. Lu <hjl.tools@gmail.com> wrote:
>> On Wed, Dec 8, 2010 at 9:36 AM, H.J. Lu <hjl.tools@gmail.com> wrote:
>>> On Wed, Dec 8, 2010 at 5:54 AM, H.J. Lu <hjl.tools@gmail.com> wrote:
>>>> 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.
>>>>>>>
>>>>>>
>>>>>> 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
>>>>
>>>> The magic section is generated by linker directly. No changes to
>>>> assembler is required.
>>>>
>>>>> else that may generate ELF objects to generate this magic object. But why
>>>>> not just ELF directly? that is what it is after all.
>>>>
>>>> My proposal isn't specific to ELF.
>>>>
>>>>>
>>>>> 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.
>>>>>
>>>>
>>>> My proposal works on both fat and slim LTO objects. ?The idea is
>>>> you can use "ld -r" on any combination of inputs and its output
>>>> still works as before "ld -r".
>>>>
>>>
>>> Here is the revised proposal.
>>>
>>
>> The initial implementation of my proposal is available on hjl/lto-mixed
>> branch at
>>
>> http://git.kernel.org/?p=devel/binutils/hjl/x86.git;a=summary
>>
>> Simple case works. ?More cleanups are needed. ?Feedbacks
>> are welcome.
>>
>
> I checked in patches to remove temporary files.
>
>

More fixes are checked in.  I will try Linux kernel next.


-- 
H.J.