Re: PA64 configure issues

[Geoff Keating <geoffk at cygnus dot com>]

> Date: Tue, 25 Apr 2000 10:23:42 -0600
> From: Jeffrey A Law <law@cygnus.com>

> In general, most developers do not need PA64 capabilities, in fact, using
> PA64 generally results in programs that are larger and slower than PA32
> programs.  My current thoughts are to have the GNU tools default to PA32
> and require special options or configure names to enable PA64 capabilities.

This is the approach we use on ppc.  The exact same constraints
exist---ppc64 binaries are less compatible, and may not be faster.  So
the toolchains default to 32-bit binaries, and switch to doing 64-bit
with the option '-maix64'.

> Right now on a PA64 capable machine config.guess will return something like
> 
> hppa2.0w-hp-hpux11.00
>        ^
>        +------  This indicates the machine has the capability to run PA64
>                 code.

It turns out to be surprisingly useful to be able to build 64-bit
binaries on a 32-bit machine.  Partly this is because AIX can build
shared libraries that contain both 32-bit and 64-bit code, but also
because the 32-bit machines turn out to be faster for compiling on
(the compiler is a 32-bit binary, of course :-).

So on aix/ppc, the toolchain can always build 64-bit binaries when the OS
support for it is there (on AIX 4.3 and higher).

-- 
- Geoffrey Keating <geoffk@cygnus.com>