[PATCH] Fix for PR15086

[Nick Lewycky]

On 13 November 2013 14:57, Rafael Espíndola <rafael.espindola at gmail.com>wrote:

> On 13 November 2013 17:39, Nick Lewycky <nlewycky at google.com> wrote:
> > Sorry, I forgot about this thread entirely. I generally don't approve
> > non-trivial changes under lib/Target and lib/CodeGen, I'd rather somebody
> > else with more assembly/object file/backend knowledge took a look.
> >
> > On 13 November 2013 07:31, Rafael Espíndola <rafael.espindola at gmail.com>
> > wrote:
> >>
> >> I *think* this is a fine improvement, but please add
> >>
> >> * A comment saying why jmp foo at PLT is not valid or when it would be
> valid.
> >> * A note in tailcallpic2.ll saying that it could be optimized to a
> >> direct call (no got, no plt). We don't implement ELF's interposition
> >> logic, but then pretend we do during codegen. This patch doesn't need
> >> to fix that, but should note that we could do better.
> >>
> >> Nick, do you agree?
> >
> >
> > I'm a little confused. Either we should implement ELF interposition logic
> > (and that means blocking inlining of interposable functions) or we
> shouldn't
>
> I agree.
>
> > -- and I think we've decided previously that we shouldn't. If the issue
> is
> > just that it's a missed optimization then that's fine.
>
> Yes, the patch in the case of tailcallpic2.ll takes us from one missed
> optimization (using GOT when we don't need) to another (using PLT when
> we don't need).
>

Sounds good to me!
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