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 08:47:51PM +0100, Thiemo Seufer wrote:
> H . J . Lu wrote:
> [snip]
> > > Well, that's sort-of true. -mipsX allows the ISA's instructions
> > > plus some processor specific ones (like e.g. eret).
> > 
> > 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.

> 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 still don't see anything wrong to use "-mips2 -m4100" to
say to generate

Code which runs on v4100 or on any MIPS II capable CPU.
Code which uses 32bit instructions only.

H.J.