Re: [PATCH] Fix distinction of 32/64bit addresses in MIPS gas

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

cgd@broadcom.com wrote:
[snip]
> yes, i know that the pointer is going to be constrainted to being a
> sign-extended 32-bit value, but neither the compiler or any assembly
> code that uses it needs to know that (or should).  As far as they're
> concerned, pointers are 64-bit values and they're loaded with ld, etc.

I see. Btw, my patch actually doesn't change this behaviour, the
HAVE_32BIT_ADDRESSES macro cares about macro expansion, so it
changes an address load via immediates from a "lui; daddiu" sequence
to "lui; addiu", this makes no difference. An "ld" isn't changed.

> yes, there's code that actually uses this.  why?  it's really nice to
> have code that is linked into a 32-bit address space, but can have
> 'usable' 64-bit pointers in C code.  e.g. code that lives at the boot
> vector, but wants to address data in xkphys...

This is something similiar to the technique used for the current
mips64-linux kernels.


Thiemo