[PATCH] D32706: [AArch64] Consider widening instructions in cast cost calculation

[Matthew Simpson via Phabricator via llvm-commits]

mssimpso added a comment.

In https://reviews.llvm.org/D32706#746122, @evandro wrote:

> Please, not yet another feature.  It should be possible, methinks, to `getSubtarget().getSchedModel()` to compare the relative costs.


I can't really comment on whether that would be possible or not, because I haven't looked at it. It seems to be somewhat tangential to this patch, though, since we currently always generate the widening instruction variants if possible, eliminating the extends. So I'm not sure how that would affect TTI. It seems like you're wanting to change instruction selection?

> Do you have a publicly available benchmark where this change is meaningful so that I can evaluate it better?  For I haven't seen any change in our workloads after this change.  Maybe, in the end, it doesn't matter; or maybe it's not that common.

Yes, this change is primarily to encourage more aggressive SLP in spec2006/h264ref. It provides a ~17% improvement on Falkor.


https://reviews.llvm.org/D32706