------- Comment #36 from rguenth at gcc dot gnu dot org 2007-05-03 21:59 ------- Well, the patch in comment #33 really does what I did with the patch to libstdc++. If we take the first patch (from comment #29) and change its effects on the alias machinery so that for
q = ALIAS_CONVERT_EXPR (p) we have two VDEFs on qs and ps alias tags like # SMT.1_2 = VDEF <SMT.1_1> # SMT.2_2 = VDEF <SMT.2_1> q = ALIAS_CONVERT_EXPR (p) (and optimize q = ALIAS_CONVERT_EXPR (p) to q = p if the types of q and p are the same, as pinskia noted), then we are safe at the tree level (the ALIAS_CONVERT_EXPR represents a load/store barrier for qs and pq type). At expansion time we'd need to do the same, which would be emitting clobbers for mem expressions representing dereferences of q/p. I believe we cannot really do better here. -- http://gcc.gnu.org/bugzilla/show_bug.cgi?id=29286
