Re: x86 abi for complex.

[Anders Magnusson <ragge%tethuvudet.se@localhost>]

Den 2023-02-02 kl. 20:29, skrev Joseph Koshy:
> On Thu, Feb 02, 2023 at 07:59:32PM +0100, Anders Magnusson wrote:
>
> > I looked at the "complex" abi code generated on NetBSD/i386
> > for function calls, and noticed a slight discrepancy.
> > For functions returning double or long double complex, the complex
> > numbers are handled as returning of structs with the same content.
> > But; for functions returning float complex, the return values are
> > returned in eax/edx and not as the corresponding struct.
> I believe that is how the i386 ABI is defined:
>
>    https://www.uclibc.org/docs/psABI-i386.pdf (page 14)
Yep, sounds quite likely.
> > What is the reason for;
> > 1) return floats in eax/edx instead as a struct?
> My guess: passing these values in registers helps
> reduce memory traffic.
I don't think so, since the values must be stored into memory anyway to 
get them into the floating point registers.

-- R