[PATCH] D37451: [x86] enable storeOfVectorConstantIsCheap() target hook

[Sanjay Patel via Phabricator via llvm-commits]

spatel added a comment.

In https://reviews.llvm.org/D37451#863494, @zvi wrote:

> Intuitively, it seems to me that choosing a minimum threshold, as suggested in note 2, is a better option.


Yes, that should be a more clear win. It should also sidestep the scalar imm -> move to vector -> store regressions we see here.

> Another concern for store-merging in general: are we more susceptible to losing store-to-load forwarding? I know that Intel pre-Nehalem processors had some limitations that were later improved. Sorry i can't recall the full details from the top of my head. Will look later at the Optimization Manual for the info.

I can see that concern in general, but we're only dealing with constant stores in this patch, so I would hope there's no problem rematerializing constants.


https://reviews.llvm.org/D37451