RFC: Add 32bit x86-64 support to binutils

Jakub Jelinek jakub@redhat.com
Fri Dec 31 10:03:00 GMT 2010


On Thu, Dec 30, 2010 at 01:42:05PM -0800, H. Peter Anvin wrote:
> On 12/30/2010 11:57 AM, Jakub Jelinek wrote:
> >>
> >> Would be nice if LFS would be mandatory on the new ABI, thus
> >> off_t being 64bits.
> > 
> > And avoid ambiguous cases that x86-64 ABI has, e.g. whether
> > caller or callee is responsible for sign/zero extension of arguments, to
> > avoid the need to sign/zero extend twice, etc.
> > 
> 
> Ehwhat?  x86-64 is completely unambiguous on that point; the i386 one is
> not.

It is not, sadly, see http://gcc.gnu.org/PR46942
>From what I can see the psABI doesn't talk about it, GCC usually sign/zero
extends on both sides (exception is 32-bit arguments into 64-bit isn't
apparently sign/zero extended on the caller side when doing tail calls),
from what I gathered LLVM expects the caller to sign/zero extend (which is
incompatible with GCC tail calls then), not sure about ICC, and kernel
probably expects for security reasons that the callee sign/zero extends.

	Jakub



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