Re: [Qemu-devel] Re: branches are expensive

[Avi Kivity <avi@redhat.com>]

Steffen Liebergeld wrote:
> I've tested Qemu 0.10.0 and with i386-softmmu on a i386 host I get the
> following numbers:
> direct jump count 70%, 2 jumps 54%
>
> For qemu-system-arm on an ARM host, the numbers look like this:
> direct jump count 47%, 2 jumps 40%
>
> For completeness I tested qemu-system-arm on a i386 host as well:
> direct jump count 44%, 2 jumps 37%
>
> So it looks like the chaining on ARM targets is not as effective as on i386
> targets (regardless of the guest, I used the same guest setup, compiled for
> different architectures, on all tests). Do you have any ideas why this is the
> case?
>   

I'd guess that predicated instructions are heavily used on ARM for 
if/else sequences, so intra-page branches would be less frequent.


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error compiling committee.c: too many arguments to function