[PATCH] D80801: [DAGCombiner] allow more folding of fadd + fmul into fma

[Sanjay Patel via Phabricator via llvm-commits]

spatel added a comment.

In D80801#2065649 <https://reviews.llvm.org/D80801#2065649>, @efriedma wrote:

> On ARM CPUs, there's a special forwarding path to reduce the latency of chains of fma isntructions, so this seems fine there even if the latency is relevant.


Thanks for that info.

Just to reiterate: the transform that this patch is making can't hurt latency unless FMA has a cost that is greater than the sum of individual FMUL + FADD. If that slow of an FMA exists somewhere, I'd be interested in learning about the design. :)


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