Re: [tree-ssa] vdefs question (to make vectorizer pass verify ssa)

[Daniel Berlin <dberlin at dberlin dot org>]

> The lines marked with '*' are the new source lines I added that solved 
> the
> problem and allowed the vectorized code to pass the verifiers.
>
> The lines marked with '->' are not required in order to successfully 
> pass
> verify_ssa, but update the may-aliases and result in vector 
> loads/stores
> that have vdefs/vuses. However, I did not find an API exposed out side 
> of
> tree-dfa.c that lets you create new mem-tags and compute may-aliases on
> demand; so for now I called compute_may_aliases(), which resulted in 
> over
> conservative vdefs/vuses - the pointers I created ended-up aliasing 
> all the
> arrays in the function,

Yeah, you'd need to enable flag_tree_points_to = PTA_ANDERSEN to get 
better results (because TBAA is type based, obviously).

> whereas if I could explicitely set their may-alias
> set in the vectorizer I would make each pointer alias only the array it
> points to. Is there an API that lets you do that?

You'll probably have to expose parts of the aliasing API in order to do 
this, since it's all internal ATM.
If they all share the same aliasing properties, you only need to create 
a memory tag and set the variables to use that memory tag.