[PATCH] D67948: [LV] Interleaving should not exceed estimated loop trip count.

[Hideki Saito via Phabricator via llvm-commits]

hsaito added a comment.

In D67948#1712213 <https://reviews.llvm.org/D67948#1712213>, @ebrevnov wrote:

> In D67948#1711380 <https://reviews.llvm.org/D67948#1711380>, @hsaito wrote:
>
> > In D67948#1710615 <https://reviews.llvm.org/D67948#1710615>, @ebrevnov wrote:
> >
> > > @hsaito, Please commit if you find this version acceptable.
> >
> >
> > @ebrevnov, I recommend you visit http://llvm.org/docs/DeveloperPolicy.html#obtaining-commit-access and obtain your own commit access. Your committed and under review patches deserve it.
> >  Thank you very much for your contribution. Let me know if you still would like me to commit this one.
>
>
> I was going to do that right after this patch lands. Please assist me (hopefully last time) in landing the patch.


OK. Please update the comment and then I'll land the patch.



================
Comment at: llvm/lib/Transforms/Vectorize/LoopVectorize.cpp:5265-5266
 
   // If the trip count is constant, limit the interleave count to be less than
   // the trip count divided by VF.
+  if (BestKnownTC) {
----------------
ebrevnov wrote:
> hsaito wrote:
> > ebrevnov wrote:
> > > hsaito wrote:
> > > > If trip count is expected to be small, limit the interleave count to be less than the trip count divided by VF
> > > There is some ambiguity in using "small" through out the code. For getSmallBestKnownTC  "small" is if it fits 32-bit. For "if (BestKnownTC && *BestKnownTC < TinyTripCountInterleaveThreshold)" check "small" is what less than TinyTripCountInterleaveThreshold. Here "small" should refer to the meaning defined by getSmallBestKnownTC .
> > > I think we better avoid using "small" one more time here to minimize the confusion.
> > Sorry for being unclear. I was suggesting an update to the comment. With this patch, BestKnownTC is not constant, right?
> I see what you are talking about. Another ambiguity here :-) BestKnownTC returns compile time constant value which may be exact runtime constant or estimated non-constant. In this case I believe "constant" means that we were able to get a compile time constant value for the trip count. How about the following wording?
> 
> // If trip count is known or estimated compile time constant, limit ....
That's fine as well.


CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D67948/new/

https://reviews.llvm.org/D67948