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Re: Plans for Linux ELF "i686+" ABI ? Like SPARC V8+ ?
On 10/15/07, Denys Vlasenko <email@example.com> wrote:
> On Monday 15 October 2007 13:18, Darryl Miles wrote:
> > Yes maybe there is a restriction in the ELF format on the maximum
> > executable size but linking has little to do with the issue of improving
> > performance via better linkage ABI rules. Passing function arguments by
> > registers [64bit] verses by stack [32bit].
> You cannot use 64bit registers in 32bit mode on x86_64.
> You also cannot use registers 8-15, neither general purpose
> nor XMM ones. They are simply not accessible at all.
> Can you elaborate what exactly can be significantly improved
> by new ABI?
The idea is to use 64bit mode but restrict (the used part of) pointers to
32bit (for example by zero-extending them or leaving the upper parts
undefined). And of course make long 32bits again. This way you
can do long long arithmetic using 64bit integer registers, have the
extra registers available but save memory.