[llvm-dev] A bug related with undef value when bootstrap MemorySSA.cpp

[Daniel Berlin via llvm-dev]

On Mon, Jul 17, 2017 at 11:18 AM, Sanjoy Das via llvm-dev <
llvm-dev at lists.llvm.org> wrote:

>  Hi,
>
> On Mon, Jul 17, 2017 at 10:32 AM, Xinliang David Li <davidxl at google.com>
> wrote:
> > The issue blocks another optimization patch and Wei has spent huge
> amount of
> > effort isolating the the bootstrap failure to this same problem. I agree
> > with Wei that other developers may also get hit by the same issue and the
> > cost of leaving this issue open for long can be very high to the
> community.
>
> I can't speak for others, but I am fine with adding a workaround for
> this.  However, I suspect isGuaranteedNotToBeUndefOrPoison in
> LoopUnswitch may regress other benchmarks.
>

Any other thoughts on a more minimal fix?
Otherwise, it sounds like we can only try to find the fix that does the
least damage.
We can't just leave it broken given it's triggering even in llvm bootstraps
now :(
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