Jingu Kang via llvm-dev
2021-Apr-07 19:35 UTC
[llvm-dev] Question about Traversing Loops in forward or reverse program order on new pass manager
Hi All, I have seen performance regressions from new pass manager against legacy pass manager. One of the issues is the order of populating loops on pass manager. The legacy pass manager is traversing loops in reverse program order but the new pass manager is traversing in forward program order. It sometimes causes different output. I have created a review https://reviews.llvm.org/D99774 for reverse program order on new pass manager and had short discussion with Arthur on it. It is not easy to say the reverse order is better than the forward one or vice versa. I would like to share this issue with more people on llvm-dev. If you have idea or experience about this issue, please share it. Thanks JinGu Kang -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://lists.llvm.org/pipermail/llvm-dev/attachments/20210407/210e0aa0/attachment.html>
Arthur Eubanks via llvm-dev
2021-Apr-15 16:59 UTC
[llvm-dev] Question about Traversing Loops in forward or reverse program order on new pass manager
Ping on loop traversal order. Does anybody have any intuition about which way to traverse loops in a function? On Wed, Apr 7, 2021 at 12:36 PM Jingu Kang via llvm-dev < llvm-dev at lists.llvm.org> wrote:> Hi All, > > > > I have seen performance regressions from new pass manager against legacy > pass manager. One of the issues is the order of populating loops on pass > manager. The legacy pass manager is traversing loops in reverse program > order but the new pass manager is traversing in forward program order. It > sometimes causes different output. I have created a review > https://reviews.llvm.org/D99774 for reverse program order on new pass > manager and had short discussion with Arthur on it. It is not easy to say > the reverse order is better than the forward one or vice versa. I would > like to share this issue with more people on llvm-dev. If you have idea or > experience about this issue, please share it. > > > > Thanks > > JinGu Kang > _______________________________________________ > LLVM Developers mailing list > llvm-dev at lists.llvm.org > https://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev >-------------- next part -------------- An HTML attachment was scrubbed... URL: <http://lists.llvm.org/pipermail/llvm-dev/attachments/20210415/4a609f99/attachment-0001.html>