About mtune=atom

[Jakub Jelinek]

On Mon, Jan 24, 2011 at 12:55:59PM -0500, Bill Nottingham wrote:
> Jakub Jelinek (jakub at redhat.com) said: 
> > On Mon, Jan 24, 2011 at 09:25:45AM -0800, John Reiser wrote:
> > > Actually many of them should be using the new x86_32 software architecture,
> > > which is the 64-bit instruction set (thus 16 "general" registers, SSE, ...)
> > > but with integers, longs, and pointers all 32 bits.  The upper 32 bits
> > > of any user address are 0, and not stored in RAM (except the return address
> > > of CALL.)  This gives a measurable benefit on boxes with low RAM.
> > 
> > Except that such a model is only barely supported in binutils, the support
> > for it in gcc is pre-alpha state on a branch and there is no kernel nor
> > glibc support.
> 
> Am I missing something, or would this also be binary-incompatible? If so,
> that's very very very much not worth the effort.

Yes, it is ABI incompatible, not sure what made hjl start with that now
and trying to push x86_64 into Irixy shape with 3 multilibs instead of 2.
I vaguely remember we've talked about it a decade ago and decided it was not
worth the effort.

	Jakub