2011/12/29 Tatsuo Ishii <is...@postgresql.org>
> > Impressive results.
> >
> > config/c-compiler.m4 doesn't seem like the right place for the
> > configure test. Would there be any harm in setting the lwarx hint
> > always; what would happen on older ppc processors that don't support
> > it?
> I think the load module just fails to run in this case, but I'd like
> to confirm. Ori-san?

I don't know where is the right config/*.m4 to place this kind of
configure test. Do you have any idea?

I believe lwarx hint would be no harm for recent PowerPC processors.
What I tested are:

  (1) Built postgres on POWER6 + RHEL5, which got lwarx hint
      included. Then copy these src tree to POWER5 + RHEL4 and
      run "make test", finished successfully.

  (2) Lwarx test in configure failed on POWER5 + RHEL4.

Note that POWER6 understands lwarx hint and POWER5 doesn't.
RHEL5 binutils supports lwarx hint and RHEL4 binutils doesn't.

The only concern is for very old PowerPC.
Referring to Power Instruction Set Architecture manual(*1), on
some processors that precede PowerISA v2.00, executing lwarx with
hint will cause the illegal instruction error.

Lwarx test in configure should fail on these kind of processors,
guessing from my test(2).

(*1) p.689 of

Manabu Ori

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