Re: Target CPU default selection on alpha

[Jeffrey A Law <law@upchuck.cygnus.com>]

  In message < 13946.51325.27183.182995@xayide.TechFak.Uni-Bielefeld.DE >you writ
e:
  > Currently gcc/configure.in sets TARGET_CPU_DEFAULT for alpha* targets based
  > on the cpu type of the machine used to configure and build gcc, as
  > determined by config.guess (alpha, alphaev5, alphaev56, alphapca56,
  > alphaev6).  While this is convenient for a single machine, I suppose it may
  > cause problems when the resulting gcc is run on a machine with a different
  > cpu type: e.g. configured for a 21164/ev5, but run on a 21064/ev4.
  > 
  > I'm not sure if this really causes problems on various alpha cpus
  > (cf. SPARC: using hardware multiplication on SPARC V7 machines causes
  > kernel emulation of the relevant instructions), but its more in line with
  > the treatment of other processors to leave this choice to the user (via
  > --with-cpu=).
There's two choices.

1. Generate appropriate code for whatever system you're building on.

2. Generate code for the least common denominator.


Sounds like gcc defaults to #1 for Sparcs, which is fine.  If you want to
generate "common" mode binaries, then you need to configure for the target
which is the least common denominator for your systems.

jeff