[PATCH] D21948: [DSE] fix - missing store to runtime stack in thunk with tail call bvval arg

[Eli Friedman via llvm-commits]

On Sat, Jul 2, 2016 at 6:35 PM, Gerolf Hoflehner <ghoflehner at apple.com>
wrote:

>
>
> Sent from my iPhone
>
> > On Jul 2, 2016, at 5:15 PM, Eli Friedman <eli.friedman at gmail.com> wrote:
> >
> > eli.friedman added a subscriber: eli.friedman.
> > eli.friedman added a comment.
> >
> > Special-casing this in DSE makes no sense... alias analysis should
> always return the correct result.
> >
> > In this case, alias analysis is correct; the definition of "tail"
> doesn't allow marking this call.
>
> Why?
>
>
It could work in theory, but in practice it isn't documented in LangRef and
isn't actually supported by the current implementation; tailcallelim
doesn't mark calls with byval arguments as "tail", optimization passes
aren't expecting it, and targets aren't expecting it.  I mean, it could be
changed, but it's not just a simple bugfix.

-Eli
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