[LLVMdev] Removing AvailableExternal values in GlobalDCE (was Re: RFC: ThinLTO Impementation Plan)
Duncan P. N. Exon Smith
dexonsmith at apple.com
Thu Jun 4 17:02:26 PDT 2015
> On 2015 Jun 4, at 16:51, Reid Kleckner <rnk at google.com> wrote:
>
> On Thu, Jun 4, 2015 at 3:58 PM, Duncan P. N. Exon Smith <dexonsmith at apple.com> wrote:
> > Personally, I think the right approach is to add a bool to createGlobalDCEPass defaulting to true named something like IsAfterInlining. In most standard pass pipelines, GlobalDCE runs after inlining for obvious reasons, so the default makes sense. The special case is the LTO pass pipeline, where the code will be reloaded and reoptimized later. IMO it's natural to put the customization there.
>
> That's a good point. But I still like these as separate passes.
>
> Hm, yeah, that's pretty sane. So, add a pass to downgrade available_externally global definitions to declarations with external linkage, add it to the standard -O2 pass pipeline, ensure that it's not part of LTO, and then call it done?
SGTM.
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