DSE and maskstore trouble

[Andrew Stubbs]

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.

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.

Confused. :-(

Andrew