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


On Mon, Dec 6, 2010 at 4:05 PM, H.J. Lu <hjl.tools@gmail.com> wrote:
>>
>> Without slim lto you never know if a duplicate symbol is a mistake
>> of the programmer or just the "fat lto" copy. Also ELF semantics
>> like weak are hard if you have multiple copies.
>>
>
> It isn't easy, but doable.
>

Here is my proposal.  Any comments?

Thanks.


-- 
H.J.
---
â 2 kinds of object files
	â non-IR object file has
		Â non-IR sections
	â IR object file has
		Â IR sections
		Â non-IR sections
â The output of "ld -r" with mixed IR/non-IR objects should work with:
	â Compilers/linkers with IR support.
	â Compilers/linkers without IR support.
â Add the mixed object file has
	â IR sections
	â non-IR sections:
		Â Object codes from IR sections.
		Â Object codes from non-IR object files.
	â Object-only section:
		Â Section name won't be generated by any tools, something like
".objectonly\004".
		Â Contains non-IR object file.
		Â Input is discarded after link.
â Linker action:
	â Classify each input object file:
		â If there is a ".objectonly\004" section, it is a mixed object file.
		â If there is a IR section, it is an IR object file.
		â Otherwise, it is a non-IR object file.
	â Relocatable link:
		Â Prepare for an object-only output.
		Â Prepare for a regular output.
		Â For each mixed object file,
			â Add IR and non-IR sections to the regular output.
			â For object-only section:
				Â Extract object only file.
				Â Add it to the object-only output.
				Â Discard object-only section.
		Â For each IR object file,
			â Add IR and non-IR sections to the regular output.
		Â For each non-IR object file,
			â Add non-IR sections to the regular output.
			â Add non-IR sections to the object-only output.
		Â Final output:
			â If there are IR objects, non-IR objects and the object-only
output isn't empty:
				Â Put the object-only output into the object-only section.
				Â Add the object-only section to the regular output.
			â Remove the object-only output.
	â Normal link
		Â Prepare for output.
		Â For each mixed object file,
			â Compile and add IR sections to the output.
			â For object-only section:
				Â Extract object only file.
				Â Add it to the output.
				Â Discard object-only section.
		Â For each IR object file,
			â Compile and add IR sections to the output.
		Â For each non-IR object file,
			â Add non-IR sections to the output.


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