[llvm-dev] An issue with "lifetime.start" and storing "undef"

[raghesh via llvm-dev]

Hi Tim,

Are you suggesting solution 3? i.e,. To add 'metadata', to SI so that the
AddressSanitizer ignores SI.

Regards,
------------------------------
Raghesh Aloor
AMD India Pvt. Ltd.
Bengaluru.
------------------------------


On Tue, Sep 24, 2019 at 2:27 PM Tim Northover <t.p.northover at gmail.com>
wrote:

> Hi Raghesh,
>
> On Tue, 24 Sep 2019 at 09:26, raghesh via llvm-dev
> <llvm-dev at lists.llvm.org> wrote:
> > In order to confine the scope of a local variable allocated using
> "alloca", we had written a pass named 'undeflocal'. This helps avoid pseudo
> phi nodes inserted because of the path (carrying an undefined value)
> starting from the "entry" block. This unwanted phi instruction was
> preventing some of the optimizations from getting triggered later on.
>
> It sounds like this is the real problem. Whatever's seeing that store
> you're inserting and using it to improve the phi should also be taught
> about @llvm.lifetime.start.
>
> Cheers.
>
> Tim.
>
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