[PATCH] D124867: [SLP][NFC] Pre-commit test showing horizontal reduction preventing FMA

[Bill Schmidt via Phabricator via llvm-commits]

wjschmidt added a comment.

In D124867#3506218 <https://reviews.llvm.org/D124867#3506218>, @ABataev wrote:

>>> Also, why these sequences are not optimized by InsrtuctionCombiner to FMA?
>>
>> Phase ordering -- it seems the FMA combining happens quite late in the pipeline.  When we replace the adds with a horizontal reduction, the opportunity is removed.
>
> Why, could you investigate it?

I'll have to refresh my memory, but my recollection is that the FMA combining is done in the MI level instruction combiner.


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