Re: [Qemu-devel] Re: OSS audio debugging

[Fabrice Bellard]

Mike Nordell wrote:

> DOOM Shareware - this one needs no introduction.
> Crashes, hangs and plays really "choppy" sound.
> The crashes and hangs (depending on moon-phase) seems to be due to
> incomplete detection of self-modifying code. When it does run for more than
> 1 second, the choppy sound I suspect might be, as for many cases here, due
> to timing or incorrect SB16, PIC or DMA emulation. That it also run as in
> molasses (the seconds I got it to run) further strengthen my suspicions of
> timing or PIC - even that it could be a large amount of self-modifying code
> invalidating the TB all the time too. I haven't dug deeper into it.

It should work now. The problem was linked to self modifying code and 
cpu interrupts.

DOOM is a rather pathological case for self-modifying code and it slows 
QEMU a lot (although DOOM remains fully playable on my PC). Since only 
some instruction constants are modified in the code, I could optimize 
this case specifically in the dynamic compiler.

Fabrice.