Re: Target CPU default selection on alpha

[Jeffrey A Law <law at hurl dot cygnus dot com>]

  > >From a quick check of current CVS configure.in, the c*-convex-*, several
  > hppa1.1-*-* and hppa2*-*-*, the i[4-7]86-*-* and alpha*-*-* targets behave
  > this way.  All others default to the least common denominator.
  > 
  > > There isn't any kind of consistency in this area.  For example the ppc
  > > defaults to "common" mode.
  > 
  > Than perhaps now it's time to become consistent, or at least document why
  > some targets have a different default.
I don't think we need to be consistent in this area.  Doing so can greatly
impact performance on some machines.


  > What are the primary arguments against defaulting to least common
  > denominator, beyond performance?
Performance.

  > I think the decision should be left to the user.  Or at least the user
  > should be aware of the choice and it's consequences.
The user still has the ability to configure for a common toolchain by using
the least common denominator configure string.  Most (all) ports also have
options which allow for generation of code for a particular processor.  So
for the PA one could configure with:

configure hppa1.0-hp-hpux10.20

Which would build a compiler which defaulted to hppa1.0 code generation, which
is the least common denominator for the PA architecture.

Or, given any PA compiler, the user can force code generation for a particular
chip with -mpa-risc-X-Y where X-Y represents different variants within the
PA family (1-0, 1-1, 2-0, and so on in the future).

jeff