Re: Does -march=r5000 imply HAVE_64BIT_GPRS?

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

H . J . Lu wrote:
> On Fri, Aug 17, 2001 at 07:35:37PM +0200, Thiemo Seufer wrote:
> > > > 
> > > > Well, and why shouldn't an arch be allowed to use a ISA below it's
> > > > default _and_ it's arch specific insns in the same code?
> > > 
> > > That is exactly what my patch does.
> > 
> > No, your patch replaces the specified -march= by the default arch
> > for the also given -mips* option, while leaving -mtune= as is.
> 
> Only for BFD, not for assembler. Besides, when -mips2 is used with
> -march=r5000, the assembler shouldn't use any instructions which are
> in r5000, but not in MISP II.

Well, now I can reiterate my question: Why shouldn't it do so?

Of course, in the case of r5000 this makes no difference since it
has no insns which aren't covered by an ISA (WRT binutils). An
example might be the VR4100: Restrict it to MIPS II but use it's
"standby" and "suspend" opcodes. With runtime CPU detection it is
easy to find a scenario where this makes sense.

> > > With "-march=r5000 -mips2",
> > > currently we set the ISA level to MIPS4 in BFD. That is my
> > > original problem. My patch will change it to set the ISA level
> > > to MIPS2 in BFD.
> > 
> > With your patch,
> >     -march=r5000 -mips2
> > effectively results in
> >     -march=r6000 -mtune=r5000 -mips2
> 
> Not exactly, my patches only applies -march=r6000 to the BFD flags. As
> for the assembler, it is still -march=r5000 -mips2.

Right. We are both talking about header flags, not code generation.


Thiemo