thread-ready ABIs

[Ulrich Drepper <drepper at redhat dot com>]

The time is near when we (well, I) well start a drastic move toward
generally using thread registers.  Even in non-threaded code.

This means that unless all architectures get thread registers (or
equivalent things like Alpha's special code) we'll have a two class
society of platforms where all code written for the platforms without
thread register can be run on the other systems, but not vice versa.

>From what I see today we have thread registers only on Alpha, x86,
IA-64, SH, and x86_64.  SPARC shouldn't be too much of a problem.  Sun
is using %g6 or %g7 (forgot which one) and since they define the ABI
no big complications are expected.

Now, what is about the rest?  I assume cris isn't much of a problem
since it's a purely embedded machine.


Arm: don't know whether this should fall in the same category.
Philip?


m68k: Well, maybe it's time to retire these machines.  But on the
other hand, there are those useless address registers.  Andreas, Jes?


PPC (32-bit) is known to be a problem.  I've seen several proposals as
to what register to use but haven't seen a final decision.  Problems
with the different PPC implementations are probably hindering this.
Geoff, could you please make a decision?  I hope the PPC64 ABI already
allocated a thread register.


S390: I have no idea.  Martin, please comment and make a decision.


MIPS: Who feels responsible?  Andreas, HJ?


PA: no idea.  HP has no 32-bit ELF so.  But they have 64-bit ELF and
it definitely has a thread register.



Please consider this a high priority task now.  I've been warning
about this for a long time.  Jakub is working on some code and once
this is ready for me to use I'll make lots of changes to ld.so and the
locale handling and from that point on we have the two classes of
architectures.

Oh, this now also concerns Hurd.  So, Roland, how far is using LDTs on
Hurd/x86?

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