Re: [Qemu-devel] qemu vs gcc4

[Laurent Desnogues]

K. Richard Pixley a écrit :
> Well, perhaps.  Except that with gcc, we get to leverage the ongoing gcc 
> optimizations, bug fixes,  new cpu support, debugger support, etc.  
> Granted, not all of these are going to be relevant to the qemu 
> environment, but in a contest between gcc generated code and qemu 
> generated code, I'll bet on gcc most days.
>
> No doubt there are times when a gcc optimization takes so long that it 
> costs more time to optimize than would be won back by the running code.  
> Presumably, qemu generated code would be able to make better decisions 
> here.  Except that we're not talking about using gcc in real time, are 
> we?  So essentially we have near infinite time for optimizations.

One emulated instruction is a small C function with very little
opportunity for optimization.

On top of that, for instance, calculating flags can be done much
more efficiently at assembly level by using host flags.

All what gcc brings here is portability.


                        Laurent