Re: GCCFLAGS for gcc 3.3.x (-march and _MIPS_ISA)

[Thiemo Seufer <ica2_ts@csv.ica.uni-stuttgart.de>]

Ralf Baechle wrote:
> On Tue, Aug 12, 2003 at 08:51:18AM +0200, Thiemo Seufer wrote:
> 
> > >   GCCFLAGS += -mabi=32 -march=mips2 -mtune=r4600 -Wa,--trap
> > > (or       GCCFLAGS += $(call check_gcc, -mcpu=r4600 -mips2, -mabi=32 
> > > -march=mips2 -mtune=r4600) -Wa,--trap)
> > > 
> > > Isn't it?
> > 
> > -march=mips2 is an alias for -march=r6000, I don't think that's a
> > good choice.
> 
> Why? MIPSII / MIPS32 are the highest ISAs supported for building 32-bit
> kernels so that makes sense.

Because you get only MIPS II instructions then. This doesn't matter
much for R4600, but the improvements of later ISAs won't be used.

-mabi=32 -march=r4600 works for 32bit kernels with newer toolchains,
there's no need to use -mtune separately.


Thiemo