[patch] Shark reroute LLVM atomic intrinsics to Zero

[Xerxes Rånby]

Andrew Haley skrev:
> Robert Schuster wrote:
>
>   
>> Xerxes Rånby schrieb:
>>     
>>> Greetings,
>>> This patch will make shark reroute LLVM atomic intrinsics to the
>>> existing atomic operations implemented in Zero.
>>>
>>> This patch are both platform and arch independent.
>>> I have tested this patch on Shark compiled for X86, PPC and ARM.
>>>       
>> I would make this rerouting optional depending on the architecture.
>> LLVM has atomic intrinsic fucntion support for x86(-64), powerpc (32,64)
>> and alpha. On those architectures you really want to use what LLVM
>> provides.
>>
>> E.g. on x86 the function is converted into a series of machine
>> instructions and no function call.
>>     
>
> Definitely; we really don't want a function call just do do an atomic
> cmpxchg.  This is really just a workaround for an llvm bug, and hopefully
> it'll soon go away.
>
> Andrew.
>   
I have done a small investigation to see how large the cost is to use 
the reroute patch on PPC.
The test machine is a PowerBook G4 1.333Ghz with F10 installed.

I used Caffeine Mark 3.0 for this benchmark, why? It is a quick 
benchmark and it includes some graphics tests so it is quite fun to 
benchmark with. And not to mention it is fun to see large scores since 
it is a rather old test.

To my surprise one test, the image test, actually performed a little 
better with the atomic reroute patch applied.

The nice attached pdf and ods report contains all hard data with nice 
graphs and build instructions.

For fun I have also attached two screen shots with the output of CM30 
running on F10/PPC zero and my PPC shark build.
It are nice to see that float performance have increased 14x using shark 
compared to pure zero :)

Cheers and have a great day!
Xerxes
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