Re: [patch 4.1.3] Correctly handle zero operands with gcc on PA

[John David Anglin]

> > The narrow kernels don't support the 64-bit runtime.
> 
> I don't think I was aware there was a 32-bit kernel mode.  That
> happens on sparcv9 solaris too, where a native build will fall-back
> automatically to the 32-bit ABI.  If that doesn't already happen on
> hpux then I'd like to make it so.

I don't believe that it does.  Machines that run the narrow PA 2.0
kernel are fairly rare.  I think the early machines contained PDC (ROM)
code that didn't provide the features needed for the wide kernel.

I believe that even the narrow PA 2.0 kernels do 64-bit register
saves when saving the process context so that is possible to perform
64-bit operations between calls.

> > For this reason, config.guess does an additional
> > check on CC to determine the properties of CC.
> 
> We don't drive the ABI from the compiler, but rather the other way
> around.  We establish default CFLAGS for the requested (or best
> possible) ABI.
> 
> I'm aware this ABI scheme is specific to gmp, but very few other gnu
> packages care about the level of detail we do.
> 
> > The main issue is that the straight-forward configure command doesn't
> > work.  Configure has selected the "2.0w" ABI when gcc is generating
> > code for the 32-bit runtime.
> 
> My understanding is that gcc is built either 32-bit or 64-bit, so you
> need to use the right one.
> 
> In the next gmp we'll be checking sizeof(long) to see what sort of gcc
> we've got, to let the default ABI fallback to what works.  (gmp 4.1
> pre-dated any gcc support for 2.0, hence the lack of any mention of it
> in the configure.)

Checking the sizeof(long) would certainly work on the PA to determine
whether gcc is 32-bit or 64-bit.  The __LP64__ define is another way
to tell.

There are also the arch predefines that I mentioned.  These tell you the
code level of the compiler.  The _PA_RISC1_1 and _PA_RISC2_0 defines
have been in gcc for some time.  The _PA_RISC1_0 define was added in 3.3.
The HP compiler also generates these define.

Dave
-- 
J. David Anglin                                  address@hidden
National Research Council of Canada              (613) 990-0752 (FAX: 952-6602)