dataflow branch merging plans.

[Kenneth Zadeck <zadeck@naturalbridge.com>]

I believe that the dataflow branch is now ready to merge into the
mainline.  We have fixed almost all of the performance problems
associated with it.  While there are still some left, we feel
confident that these can be addressed during the rest of stage I and
during stage II.

At this point there is one known correctness regression
(fp-int-convert-float128-timode.c on the x86-64).  This is being
addressed.

I believe we are near or better on generated code on all platforms
than the current trunk.  The only spec performance regressions that we
have seen are tracable to the dataflow branch generating fewer
instructions and you get unlucky sometimes. This has been confirmed by
Vlad in his latest spec runs.

Serge Belyshev has confirmed that the branch builds an runs the x86-64
kernel.  

At this point, we know that the branch works correctly for x86-32,
x86-64, ppc-32, ppc-64 and ia-64 and sh.  We have not recently tested
the arm, spu, mips, z390, and spark.  These did work at some point but
need to be retested to see if any regressions have crept in.

We know there are regressions in the 68k, alpha and the pa-risc.
During the next few days we would like to work on clearing the 68k
regressions.  The alpha port needs attention from someone interested
in maintaining the port.  The pa is abusing regs_ever_live and this
will be addressed after the merge.

When ARM, SPU, Mips, SPARC, and z390 are reconfirmed, approximately
nine ports will work, which is well beyond the criteria approved for
the merge.

While the majority of the hard technical issues have been vetted with
the proper maintainers, most of the patches have not been looked at by
the people who care about the formatting and coding standards (or else
my typing skills have improved dramatically.)  I would invite anyone
who wants to comment on any part of the branch to do so in the next
few days.  You should take a diff with truck revision 124834, the
revision we merged with last Friday.  If you are going to send
comments based on this diff, please make sure to include enough
context to easily find the places that need to be fixed.  This is a
very large patch.

At this point I am closing the branch to improvement except for:
1) comments from above
2) those patches that directly fix regressions or
make more ports work.
3) one patch from Seonbae Park and a few patches from Paolo Bonzini
that are in the queue and will most likely go in today.

I hope to merge this into the truck around the first of next week.  

Thanks everyone for all of the help on this branch.

Kenny