On Mon, Apr 28, 2014 at 1:39 PM, Chandler Carruth <chandl...@google.com> wrote: > I think the real question is -Oz. My understanding is that the SLP > vectorizer should always make code smaller. > > I don't think matching the loop vectorizer is important. I think the > expectations of -O flags are not about the vectorization of code, but about > the trade-offs between user experiences. While I've mentioned it on other > threads: > > O1: quickly optimize what you can > O2: our general ideal tradeoff between compile time and optimizations > O3: (i wish we didn't have it) burn more compile time and/or binary size to > try and dig out some optimizations. > Os: optimize, but try to make the resulting code smaller where possible. > Oz: do anything necessary to make code smaller, even things that hurt > performance > > My impression was that SLP vectorization made sense at least for 2, 3, s, > and z. If the compile time is low enough, maybe for O1 as well. >
This makes sense to me. Partially my problem for not looking at what Chad wrote enough to go more than "at O0? why?" and forgot to look at the rest. -eric > > > On Mon, Apr 28, 2014 at 1:09 PM, Chad Rosier <mcros...@codeaurora.org> > wrote: >> >> One argument for matching the behavior of the loop vectorizer is that it's >> probably what the user expects. >> >> > Hi Chandler, >> > The discussion was in the PR as well as via IRC. I'm certainly not >> > against continuing the discussion. >> > >> > I believe everyone strongly agrees this shouldn't be on at -O0; Let me >> > know if you feel otherwise. The decision to match the behavior of the >> > loop vectorizer at -O1 and -Oz was mostly arbitrary and I have no strong >> > feelings either way. >> > >> > What are your thoughts? >> > >> > Chad >> > >> >> On Mon, Apr 28, 2014 at 12:30 PM, Chad Rosier >> >> <mcros...@codeaurora.org>wrote: >> >> >> >>> -O1, and -Oz >> >> >> >> >> >> Wait, why? Based on what discussion? >> >> >> >> This is a pretty significant change, I'd like to understand why it was >> >> made. >> >> >> > >> > >> > -- >> > Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum, >> > hosted by The Linux Foundation >> > >> >> >> -- >> Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum, >> hosted by The Linux Foundation >> > > > _______________________________________________ > cfe-commits mailing list > cfe-commits@cs.uiuc.edu > http://lists.cs.uiuc.edu/mailman/listinfo/cfe-commits > _______________________________________________ cfe-commits mailing list cfe-commits@cs.uiuc.edu http://lists.cs.uiuc.edu/mailman/listinfo/cfe-commits
