[PATCH] D38336: Add an @llvm.sideeffect intrinsic

[Dan Gohman via Phabricator via llvm-commits]

sunfish added a comment.

In https://reviews.llvm.org/D38336#882813, @dberlin wrote:

> Is literally the only purpose to handle infinite loops?
>  If so, please tighten up the description a bit.
>  (Right now "indicate that the loop shouldn't be optimized away even if it's an infinite
>  loop with no other side effects."  would cover unreachable loops, etc).


Another potential use was mentioned here <http://lists.llvm.org/pipermail/llvm-dev/2015-July/088114.html>.

> Do you expect it to keep provably finite loops that have it alive.
>  IE a loop where we can prove the backedge is not taken?

No; a backedge can still be folded away in the normal ways. The `llvm.sideeffect` call would remain, no longer needed, but not invalid. If it were important, we could add code to remove it in that case, but the patch here doesn't have that.


Repository:
  rL LLVM

https://reviews.llvm.org/D38336