[llvm-dev] Heap Exhaustion during 'DAGCombiner::Run'

[Nirav Davé via llvm-dev]

Martin:

I suspect this is an issue with post-DAG legalization store merging in the
DAGCombiner. If you have a custom lowered type the DAGCombiner may end up
merging a set of stores and immediately splitting them up in legalization.
You should be able to disable this pass universally by overriding
mergeStoresAfterLegalization() or conditionally for cases that shouldn't
match with canMergeStoresTo.

You should able able to verify by finding the loop of nodes considered with
"-debug" on.

-Nirav




On Sun, Feb 25, 2018 at 9:36 AM Martin J. O'Riordan via llvm-dev <
llvm-dev at lists.llvm.org> wrote:

> Hi LLVM-Devs,
>
> I am in the process of updating our out-of-tree implementation from v5.0 to
> v6.0 RC3, and while it builds and mostly runs, I am having trouble with a
> small number of tests where the 'WorklistMap' in 'DAGCombiner::Run' never
> becomes empty.  This is resulting in a runaway state of continuous heap
> allocation until the process exhausts all system memory.
>
> But I can't get a handle on why it is doing this, and it is not obvious to
> me that the changes between v5.0 and v6.0 RC3 invalidate our implementation
> in a way that might cause this.  The only time I see our code entered is
> when lowering is called for vector element insert by 'LegalizeOp'.  Does
> anybody have an advice on how I should approach debugging this?
>
> Thanks,
>
>         MartinO
>
>
> _______________________________________________
> LLVM Developers mailing list
> llvm-dev at lists.llvm.org
> http://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.llvm.org/pipermail/llvm-dev/attachments/20180301/62c105ca/attachment.html>