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

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

On Sun, Nov 04, 2001 at 10:31:53PM +0100, Thiemo Seufer wrote:
> H . J . Lu wrote:
> [snip]
> > > > What is wrong to select a different default processor at the run-time?
> > > > What is wrong to select a different default processor which supports
> > > > a super set of the ISA?
> > > 
> > > That's what -march/-mtune are good for. -mipsX has the problem of
> > 
> > The problem is -march/-mtune doesn't work right for 32bit instructions
> > without -mabi=32. But -mabi=32 doesn't work with the current gcc.
> 
> Do you know what's gcc's the problem here (besides of the option's
> deactivation, of course)?

I don't know.

> 
> > > having different meanings depending on the context. E.g. -mips2
> > > could mean:
> > > 
> > > - Code which runs on r6000.
> > > - Code which runs on any MIPS II capable CPU.
> > > - Code which uses 32bit instructions only.
> > > 
> > > The latter two are side effects of the first one.
> > 
> > Given today's gcc/gas, what do you suggest we should do if we want to
> > generate 32bit instructions and accept the CPU specific instructions
> > for a CPU, which supports MIPS 3 and above, without modifying the
> > source code?
> 
> I would try -march=vr4100 -mfp32 -mgp32.
> 

How can it work? I cannot pass -mips3/-march=vr4100 to gcc since it
may generate 64bit codes. Basically, I have to pass "-mips2" to gcc.
But -mips2 is not comaptible with -march=vr4100 in the current gas.
So if I pass -mips2 to gcc, which will be passed to gas, I can't add
-march=vr4100 to gas.


H.J.