Re: [Qemu-devel] /* XXX: suppress this hack */

[Johannes Schindelin]

Hi,

On Sun, 10 Oct 2004, Magnus Damm wrote:

> Hi,
>
> Better performance for i386-softmmu under PowerPC? Yes, please!
> At line 96 in "dyngen-exec.h" sits the following code:
>
> /* XXX: suppress this hack */
> #if defined(CONFIG_USER_ONLY)
> #define AREG4 "r16"
> #define AREG5 "r17"
> #define AREG6 "r18"
> #define AREG7 "r19"
> #define AREG8 "r20"
> #define AREG9 "r21"
> #define AREG10 "r22"
> #define AREG11 "r23"
> #endif
>
> I would like to "suppress that hack", ie make sure that AREG4 to AREG11
> gets defined for i386-softmmu. Someone that knows the code - what needs
> to be done? Just removing the ifdef does not work for sure. Is it some
> issue with setjmp()/longjmp()? I'm willing to set aside some hours to
> fix this if someone who knows points me in the right direction.

It's all about ABIs: see

http://www-106.ibm.com/developerworks/linux/library/l-ppc/#h4

You want all those registers you use to be volatile, i.e. every function
which wants to use one of those has to make sure that their original
contents gets restored before returning.

Hth,
Dscho