Re: [ast-optimizer-branch]: SSA-CCP on tree-ssa

[Daniel Berlin <dan at cgsoftware dot com>]

On Thu, 6 Dec 2001, Diego Novillo wrote:

> On Thu, 06 Dec 2001, Daniel Berlin wrote:
>
> > > Even if it means duplicating some code, I'm trying to
> > > figure out which option is easier to maintain in the future.
> > To be honest, I think it's easier to maintain ssa-ccp with function
> > pointers.
> > Besides the only real difference being in the evaluation function, and
> > walking the SSA, it would also enable us to vary the optimization
> > performed based on -O level or something, or combine it with other
> > optimizations just by plugging in a seperate function.
> >
> OK then.  Thanks for the clarification.  If it will make our life
> easier, I'm all for it.

>
> > > You don't mention bootstrap/regression test results. Particulary,
> > > using -ftree-ssa.  On the branch we should make -O2 trigger the
> > > tree SSA transformations.
> > Bootstraps okay on powerpc-linux-gnu.
> >
> With -ftree-ssa in BOOT_CFLAGS?
Yes.

>
> > Never got to checking test results.
> >
> We need to make sure it doesn't introduce regressions.  Since
> it's going into the ast-branch that's not such a high priority
> right now.
>
> Are you willing to keep maintaing it regularly?
Sure, i already planned on it[1].

 >  I'd like to
> merge the branch into the trunk for the 3.2 release.  If not, I
> can take over as I'll be doing lots of maintenance on the branch
> over the next few weeks.

Good to hear!

>
> Thanks.  Diego.
>
[1] I've been writing (whenever i sit around tired of coding or waiting
for compiles, so it's somewhat slow going) a guide to writing optimization
passes for gcc for those who understand compiler optimization, but have
never dealt with implementing them in gcc before.  Right now, we only have
a guide to RTL, and a guide to trees, but no guide on things like our
basic blocks, flow graph, dataflow framework, etc. I figured if there was
a guide pointing out how these things work in gcc, and where they are,
we'd get more people willing to implement optimizations or use gcc as a
platform for research.

Pieces of the code to the tree SSA-CCP are  in the tree
based  optimization chapter.