[PATCH] D137791: [SDAG] bail out of mergeTruncStores() if there's an unknown store in the chain

Wed Nov 16 08:41:03 PST 2022

jonpa added a comment.

In D137791#3927865 <https://reviews.llvm.org/D137791#3927865>, @spatel wrote:

> In D137791#3923146 <https://reviews.llvm.org/D137791#3923146>, @jonpa wrote:
>
>> I can confirm that the patch fixes the unreduced C-smith test case also.
>
> Does the updated test/description look right?

Yes, that looks like the failure as the stg (Store 64-bits) comes after and overrwrites what the sthrl (Store Halfword Relative Long) just stored.

To test that this behavior does *not* happen (with the patch), I wonder if it would maybe be better to have a .mir test that starts before isel and then check in the debug dump that DAGCombiner does not do anything wrong.

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