[PATCH] D46336: [InstCombine] Apply binary operator simplifications to associative/commutative cases.

[Sanjay Patel via Phabricator via llvm-commits]

spatel added a subscriber: dberlin.
spatel added a comment.

In https://reviews.llvm.org/D46336#1085843, @yamauchi wrote:

> In https://reviews.llvm.org/D46336#1085279, @spatel wrote:
>
> > I think part of this has already landed with:
> >  https://reviews.llvm.org/rL331311
> >
> > There are proposals trying to do reassociation in a more complete way outside of instcombine:
> >  https://reviews.llvm.org/D45842 (this would catch the cases that I recently added to and-xor-or.ll)
> >  https://reviews.llvm.org/D41574
> >
> > This is a response to discussions on llvm-dev that instcombine is already trying to do too much. This patch goes against that idea.
>
>
> Looks like some related issues are being looked into.


I think you'll find PR37098 ( https://bugs.llvm.org/show_bug.cgi?id=37098 ) covers several of the same issues you'd like to solve.

> Where’s this discussion, and what’s the concern? Compile time?

Compile-time and general bloat of instcombine because it has no limits. Here's one link:
http://lists.llvm.org/pipermail/llvm-dev/2017-May/113184.html

There's no chance that I can explain this better than @dberlin - in fact, see comments from earlier today in https://reviews.llvm.org/D44626
Sorry for the cc, Daniel...but there's a chance you're in the same room/building? :)


Repository:
  rL LLVM

https://reviews.llvm.org/D46336