Hello, > On Wed, 2006-10-25 at 13:01 -0700, Devang Patel wrote: > > > > However, various optimizer needs to know about this special tree node. > > > > > > not really (not any more than they know about other tree codes that are > > > not interesting for them). > > > > If we take an example of Jump Threading pass then it needs to know > > about this tree node and update it properly. > That could get awful ugly.
actually, that will be trivial once jump threading updates loop properly (I have a patch for that). > > So, the passes that maniuplate loop structure need to know about > > LOOP_HEADER and others do not need to worry about LOOP_HEADER. > Passes which do code motions may need to know about it -- they don't > need to update its contents, but they may need to be careful about > how statements are moved around in the presence of a LOOP_HEADER note. Which is IMHO good, as it will at least ensure that they preserve loops, in case it is really relevant for them -- just now, I do not see how code motion could affect loop structures (unless it changes CFG) -- do you have some concrete example of transformation that might be made more problematic by the existence of LOOP_HEADER node? Zdenek
