mibintc added a comment. In D72675#1919685 <https://reviews.llvm.org/D72675#1919685>, @spatel wrote:
> In D72675#1917844 <https://reviews.llvm.org/D72675#1917844>, @wristow wrote: > > > Revisiting this patch. I think that before fixing the `-ffp-contract=off` > > problem I originally raised here, there are two questions that have come up > > in this discussion that we should first resolve. Specifically: > > > > (1) Do we want to enable FMA transformations by default (at appropriate > > optimization levels), like GCC does? That is, should FMA be done for > > targets that support it with a command as simple as the following? > > > > clang -O2 -c test.c > > > This has been discussed/tried a few times including very recently. I'm not > sure where we stand currently, but here's some background: > https://reviews.llvm.org/rL282259 > D74436 <https://reviews.llvm.org/D74436> - cc @mibintc > > And (sorry for the various flavors of links to the dev-lists, but that's how > it showed up in the search results): > http://lists.llvm.org/pipermail/llvm-dev/2017-March/111129.html > http://lists.llvm.org/pipermail/cfe-dev/2020-February/064645.html > https://groups.google.com/forum/#!msg/llvm-dev/nBiCD5KvYW0/yfjrVzR7DAAJ > https://groups.google.com/forum/#!topic/llvm-dev/Aev2jQYepKQ > http://clang-developers.42468.n3.nabble.com/RFC-FP-contract-on-td4056277.html A few weeks ago there was a discussion on cfe-dev and llvm-dev initiated by @andrew.w.kaylor and while the response wasn't unanimous, there was an overwhelming sentiment (in my opinion) that it is correct and desireable to enable ffp-contract=on by default even at -O0. I had submitted a patch to do that. However the patch caused performance regressions in about 20 LNT tests and the patch was reverted, the regression was seen on multiple architecture. I can send provide a few more details about the performance problems, I don't have a solution to the LNT regression. CHANGES SINCE LAST ACTION https://reviews.llvm.org/D72675/new/ https://reviews.llvm.org/D72675 _______________________________________________ cfe-commits mailing list cfe-commits@lists.llvm.org https://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
