David Edelsohn wrote: > -ftree-loop-linear enables a number of features and > transformations. Which part, exactly, is experimental? You are quoting > from the documentation for the option, but Dan may be referring to a > particular transformation. I thought the failure and algorithm > correctness was related to creating perfect loop nests used by other > transformations, not all of the tree loop linear. > > I think this discussion is losing a lot in the summary.
I did provide nearly all of the information that I had from Dan, but it's entirely possible that the original conversation failed to convey the full complexity of the situation to me. :-) Dan wrote (and gave me permission to repost): > It only happens with -ftree-loop-linear, a flag we have marked as > experimental. > IE it is not something that users will hit without adding extra flags to > their compiler. I don't see that -ftree-loop-linear is marked as experimental, so something seems to be confused about this situation. That quote suggested to me that the entire option was experimental. However, Dan also wrote: > I can fix almost all of these bugs by simply removing the perfect nest > conversion code, which confirms your suggestion that it's this one transformation that's experimental. However, we still have the same problems as from my original email: * We have an option which is (at least partially) experimental and known-dangerous, but we're not conveying this to users, and: * We need a general strategy for dealing with this situation in future, independent of -ftree-loop-linear. Possibly, we could solve this specific issue by creating a separate option to enable the problematic transformations -- but I'd still like to have a general strategy for dealing with such options, including the one that would be created to enable the perfect nest conversion code. -- Mark Mitchell CodeSourcery [EMAIL PROTECTED] (650) 331-3385 x713
