Re: Where is it written?

From: Andrea Arcangeli (andrea@suse.de)
Date: Sun Nov 12 2000 - 07:23:28 EST


On Sat, Nov 11, 2000 at 05:17:49PM -0600, Peter Samuelson wrote:
> I'd say go for it -- set up a mailing list and flesh out a better x86
> ABI. [..]

I think it doesn't worth to break binary compatilibity at this late stage.

> design such.) One issue: ideally you want to use 64-bit regs on AMD
> Hammer for long longs, but then you leave out all legacy x68s. :(

We can't in compatibilty mode because the rex regs are available _only_ in
64bit mode and even assuming the hardware would support that I would not
recommend that since as you said that binary would not run anymore on any other
x86 so causing pain. Recompiling a program with native x86-64 gcc 64bit (that
uses the 64bit ABI) is the right way to go in that case (64bit mode uses 1
64bit register for long long as all other 64bit architectures of course).

> AIUI gcc can cope OK with multiple ABIs to be chosen at runtime, am I
> right? IRIX, HP-UX and AIX all have both 32-bit and 64-bit ABIs.

Yes as in other systems, 32bit mode and 64bit mode needs different ABI and they
will coexist in the same system.

Andrea
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