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

[Thiemo Seufer <ica2_ts at csv dot ica dot uni-stuttgart dot de>]

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)?

> > 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.


Thiemo