[PATCH] Do not use layout-before to layout atoms.

Shankar Easwaran shankare at codeaurora.org
Thu Mar 27 14:38:59 PDT 2014

I understand your usecase, but what I meant is, dead-strip is only a 
option available in core.

Removing kindLayoutBefore completely should not affect anything because 
we dont dead strip in flavors [link, gnu, ld64]


Shankar Easwaran

On 3/27/2014 4:31 PM, Rui Ueyama wrote:
> Can you elaborate a bit? I don't understand what you mean.
> Removing kindLayoutBefore will affect dead stripping because it would 
> lost back references for kindLayoutAfter, so it would collect live atoms.
> I'm not removing kindLayoutBefore in this patch. This patch is just to 
> stop using kindLayoutBefore in the layout pass. The dead stripping 
> pass is still using it. Removing kindLayoutBefore entirety is the last 
> step, after modifying the dead stripping pass so that the pass works 
> without kindLayoutBefore (only with kindLayoutAfter and kindInGroup).
> On Thu, Mar 27, 2014 at 12:45 PM, Shankar Easwaran 
> <shankare at codeaurora.org <mailto:shankare at codeaurora.org>> wrote:
>     On 3/27/2014 2:33 PM, Rui Ueyama wrote:
>>     (I accidentally hit "reply" instead of "reply all", so sending it
>>     again.)
>>     I'll add "alias" references if no objections from other
>>     reviewers. I'll probably add ELF symbol aliasing support with it,
>>     so hold on.
>>     We cannot remove kindLayoutBefore because doing it would break
>>     dead stripping pass. We still need it for GC as GC needs backward
>>     references.
>>     To remove kindLayoutBefore, we have to modify dead striping pass
>>     so that it creates back references internally from forward
>>     references and use it while collecting dead objects. I think I'm
>>     going to make such change, but it's going a bit large.
>>     Submitting this change first and then doing the next step in a
>>     following patch would be better than merging the two together.
>>     Incremental change is easier to bisect in case it would breaks
>>     omething, and it's easy to understand for reviewers, too.
>     Do we have a flag to garbage collect atoms with lld in the current
>     implementation ? If not removing kindLayoutBefore wouldnot affect
>     anything right ?
>     Shankar Easwaran
>     -- 
>     Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum, hosted by the Linux Foundation

Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum, hosted by the Linux Foundation

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