Re: Re: SV: [Qemu-devel] ARM CPSR and conditional instructions

[Torbjörn Andersson]

We are currently debugging the situation and we are actually not sure about the 
real reason for our current situation.

However, we have seen that the condition bits in CPSR differers compared to one 
other arm instruction set simulator, running the same binary. This indicate for 
us that there might be something wrong i QEMU (translate.c op.c for ARM). 
However, it is not proven yet.

However, our understanding for the situation would improve if the strategy for 
simulating the conditional execution of ARM instructions is understood. 

Is a conditional ARM instruction treated as a branch-point, an end marker for a 
TB?
 If not, jumps qemu within a TB?   
Is it possible to describe the strategy with a reasonable effort? I would be 
very greatfull.

/Torbjörn

> Från: Wolfgang Schildbach <address@hidden>
> Till: address@hidden
> Rubrik: Re: SV: [Qemu-devel] ARM CPSR and conditional instructions
> Datum: Thu, 23 Nov 2006 08:43:50 +0100

> I very much doubt there is any problem with the CPSR. The ARM emulation 
> has correctly run hundreds of millions of instructions coming from many 
> different compilers and hand-written assembly. Can you be more precise in 
> what the effect is that you see?
> 
> - Wolfgang
> 
> address@hidden 
> wrote on 22.11.2006 22:13:01:
> 
> > I?m sorry for spamming you mailing list with my duplicate posts. I 
> > had some problems sending my mail. 
> > 
> > /Torbjörn
> > 
> > Från: address@hidden 
> > [mailto:address@hidden För 
> > Torbjörn Andersson
> > Skickat: den 21 november 2006 22:16
> > Till: address@hidden
> > Ämne: [Qemu-devel] ARM CPSR and conditional instructions
> > 
> > Hello qemu developers!
> > 
> > I´m using QEMU for some ARM debugging and I have som questions 
> > regardning the CPSR register. I get the feeling that the CPSR 
> > condition code bits, representing the results from the ALU, are not 
> > maintained at all points. Is the JIT in QEMU tailored in any way 
> > towards GCC output? (Resulting in issues with the output of other 
> > compilers that make use of the conditional execution of instructions 
> etc.)
> > 
> > What I want to do is to try to verify QEMU maintains the CPSR 
> > register and if not fix it. However, it is not trivial identify 
> > where the updates should be placed. The relationship between 
> > translate.c and op.c is not trival I must say :)
> > I would be happy I anyone here could give me some pointers on how 
> > the updates of the CPSR register is done today and what the strategy
> > is. I guess there are plenty of performance ideas here as in the rest of 
> qemu.
> > 
> > Does anyone have any reflection on this topic or can anyone give me 
> > some pointers?
> > 
> > Torbjörn
> >  _______________________________________________
> > Qemu-devel mailing list
> > address@hidden
> > <a
> href=http://lists.nongnu.org/mailman/listinfo/qemu-devel>http://listsnongnu
> .org/mailman/listinfo/qemu-devel</a>
> 
> 
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