[llvm] r225034 - InstCombine: try to transform A-B < 0 into A < B

[Chandler Carruth]

On Wed, Jan 14, 2015 at 5:53 PM, Kevin Qin <kevinqindev at gmail.com> wrote:

> Hi Michael and David,
>
> I also see some performance regressions on aarch64 target introduced by
> this commit. No further invesitgation on what's the root cause, but I guess
> the one Michael shared may cause regression on many targets, including
> aarch64.
>
> I argee with Michael's suggestion that revert this commit firstly, and
> make more performance test over it.
>

It would be good to understand whether the change David made early today
would have addressed these issues or not.

(Either way, it has made me suspect that we may want A - B < 0 to be the
canonical form, and lower it cleverly in the backend.)
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.llvm.org/pipermail/llvm-commits/attachments/20150114/b5fd604e/attachment.html>