Re: PATCH: Fix the MIPS ISA ELF setting (Re: RedHat 7.1/mips update)

["H . J . Lu" <hjl at lucon dot org>]

On Mon, Nov 05, 2001 at 03:03:30PM +0000, Richard Sandiford wrote:
> "H . J . Lu" <hjl@lucon.org> writes:
> > -mabi=32 is disabled in gcc, including the current CVS:
> > 
> >   /* ??? This doesn't work yet, so don't let people try to use it.  */
> >   if (mips_abi == ABI_32)
> >     error ("The -mabi=32 support does not work yet.");
> 
> The check's still in the 3.0 branch, but it's been removed from mainline.

It is only changed a few days ago. I don't think it is an option for Linux.

> 
> > > If it doesn't work, it's AFAICS a bug. -mgp32 -mfp32 might be useful
> > > as a replacement for -mabi=32 then.
> > 
> > The problem is I don't know for sure what gcc will do with -march=xxxx
> > where xxxx suports 64bit instructions. -mips2 seems a way to say I want 
> > 32bit instructions.
> 
> -march=xxxx -mgp32 -mfp32 should work.  The -mgp32 and -mgp64 flags
> directly control the target flag that enables or disables 64-bit integer
> instructions.  -mfp32 and -mfp64 directly control whether doubles are
> stored in single FPRs or in FPR pairs.
> 
> GCC knows that the selection of a 64-bit target isn't enough of an
> excuse to use 64-bit instructions.  It should always check these flags
> as well.
> 
> I was recently working on a MIPS IV target that was being used with the
> -mgp32 and -mfp32 options.  I had to fix a couple of places where the
> check had been forgotten (the fixes went into mainline, but not the 3.0
> branch).  Mostly things just worked.

So the -mgp32 and -mfp32 options don't work with older gcc.

Since not many binutils people believe it is nessary to provide backward
compatibility, I guess I have to just include my patch in my Linux binutils
and warn people about it.


H.J.