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Re: [ast-optimizer-branch]: SSA-CCP on tree-ssa
- From: Daniel Berlin <dan at cgsoftware dot com>
- To: Diego Novillo <dnovillo at redhat dot com>
- Cc: <gcc-patches at gcc dot gnu dot org>
- Date: Fri, 7 Dec 2001 01:01:09 -0500 (EST)
- Subject: Re: [ast-optimizer-branch]: SSA-CCP on tree-ssa
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?
> > 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.
> 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.
 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.