Re: r4600 flag

[Ralf Baechle <ralf@oss.sgi.com>]

On Tue, Jul 31, 2001 at 08:29:12AM -0700, John D. Davis wrote:

> Looking at the system map from the generic build of 2.4.3, it looks like
> the code is 64 bit.  The upper 32 bits are "f" instead of 0.

No.  Sign extended, that is bit 31 is copied into bits 32 to 63.

> I built it > using the R4600 flag.  This differs from the system map for
> 2.4.0-test9 where the upper 32 bits are 0.

No.  Different binutils.  Older binutils did zero extend 32-bit addresses
to 64-bit addresses in the objdump output which is wrong.

> For the indy, do I specify mips2 to generate 32 bit code?

-mips2 :-)

For the kernel we use a few 64-bit instructions on the Indy though.  These
are carefully chosen such that nothing go wrong like exceptions corrupting
the upper 32-bit of a register.

> objdump says it is ELF32, but it doesn't look like that.  I would like to
> generate 32bit.

ELF is an object format.  Nothing prevents you from putting 64-bit code into
a 32-bit ELF file and vice versa.  You just need to be careful.

  Ralf