On Tue, Jul 3, 2018 at 2:46 PM Andrew Stubbs <andrew_stu...@mentor.com> wrote: > > On 03/07/18 13:21, Richard Biener wrote: > > Ok, so if we vectorize the above with 64 element masked stores > > then indeed the RTL representation is _not_ safe. That is because > > while the uses in the masked stores should prevent things from > > going bad there is also TBAA to consider which means those > > uses might not actually _be_ uses (TBAA-wise) of the earlier > > stores. In the above case rtattr * doesn't alias int (or whatever > > types rta_type or rta_len have). That means to DSE the earlier > > stores are dead. > > I managed to get it to generate maskstore without the unspec, and the > code now runs correctly.
OK, that is good. > I don't follow your AA reasoning. You say the use stops it being bad, > and then you say the stores are dead, which sounds bad, yet it's not > deleting them now. If you look at RTL dumps (with -fstrict-aliasing, thus -O2+) you should see MEM_ALIAS_SETs differing for the earlier stores and the masked store uses. Now I'm of course assuming DSE is perfect, maybe it isn't ... ;) Richard. > > Confused. :-( > > Andrew
