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Re: SSA Vs unSSA
On Wed, Mar 26, 2008 at 7:36 PM, Andrew Haley <aph@redhat.com> wrote:
> Fran Baena wrote:
>
> > what are the advantages and inconvenients of get RTL from SSA rather
> > than GIMPLE (previously translated from SSA)?
>
> It would mean that the expander would have to understand and unpick
> SSA-specific stuff like PHI-nodes. It could be done, but I sure can't
> think of any reason you'd want to.
You'd want to avoid translating from tuples back to nested trees. Instead when
expanding from SSA form (ok, let's make that "semi"-SSA form that just keeps
the UD chains but gets rid of PHI nodes (and maybe overlapping life ranges))
the expander can do expression combining by following the UD chain instead
of relying on complex expressions re-constructed by TER.
My understanding is that this will (sort of) happen at the moment we get
the tuples branch merged.
Richard.