Re: [RFC] Contributing tree-ssa to mainline

[Scott Robert Ladd <coyote at coyotegulch dot com>]

Richard Kenner wrote:
> Sure, but in that situation I feel it should stay in a branch until those
> "possibilities" have indeed been "opened up".  Otherwise, it's a lot of
> extra code to maintain and overhead to pay for in compilation without any
> known benefit.  Newer is not always better.  Indeed I find that for most
> of the products I buy, the quality is often *far* worse than that of the
> same product purchased decades ago.

You are correct.

I wish I were more conversant in the internal mechanations of compilers; 
at the moment, I base my opinion on what I'm told by people who appear 
to "know their stuff."

I have two major interests in the future of GCC: OpenMP and Fortran.

When we first created the OpenMP project last year, I was informed that 
the existing GCC architecture was ill-suited to the task. Therefore, 
gomp (the GNU OpenMP project) was explicitly founded on tree-ssa. 
Perhaps someone else (Steven?) can fill in the reasons for this choice.

We've already had a debate about back-porting gfortran to the 3.4 
architecture; again, others are more qualified to define the technical 
challenges. What I do know is that the gfortran developers seem very 
focused on tree-ssa.

If we do *not* move SSA into mainline, then we need to discuss how (and 
if) these important features (Fortran 95 and OpenMP) can be implemented 
in a timely fashion under the existing architecture.

OpenMP will become a major issue within 18 months; regardless of what 
happens to Fortran, the increasing parallelism in hardware, Intel's 
strong support of OpenMP, and existing practice in high-performance 
computing all suggest that this issue is important to GCC.

> Whether or not (and to what extent) the tree-ssa infrastructure is
> "significant" can't be made by arguments over possibilities it might open
> up, but by demonstrating those possibilities.

Someone needs to step up and explain why certain new features are only 
being developed under tree-ssa. Is it due to technical concerns (as I 
understand it), or not?

--
Scott Robert Ladd
Coyote Gulch Productions (http://www.coyotegulch.com)
Software Invention for High-Performance Computing