Re: [PATCH]: Fix latent bug in tailcall

[Zdenek Dvorak <rakdver at atrey dot karlin dot mff dot cuni dot cz>]

Hello,

> > anyway, it means either running ssa update, or preserving full ssa form
> > (which we did not do for quite some time, so it would probably require
> > some changes to other parts of gcc).
> 
> Honestly, i'd rather try option 2.
> 
> I still believe the general ssa updater was a bad idea, as shown by the
> fact that it is the source of most time spent in the middle-end on a lot
> of testcases.
> 
> It is simply used as a crutch for avoiding thinking about how to
> properly update the ssa form.

when update_ssa was introduced, Diego has made some extensive
measurements that have shown it to be in fact more efficient than the
special case solutions we had implemented at that time, so the situation
is more complicated.  One of major wins with update_ssa was that
we no longer needed loop closed ssa form for virtual operands, which
saves significant amount of memory and compile time.

What are the testcases you speak about?  Perhaps reintroducing
special-case handling and/or improving efficiency of update_ssa
might be appropriate for them.

Zdenek