Hi,

You can also test your primop with a foreign primop.

See here for an example of assembly code (calling cpuid):
https://github.com/hsyl20/ViperVM/blob/master/src/lib/ViperVM/Arch/X86_64/cpuid.c

And here for the Haskell part with the foreign primop that calls the assembly code:
https://github.com/hsyl20/ViperVM/blob/master/src/lib/ViperVM/Arch/X86_64/Cpuid.hs#L56

Cheers,
Sylvain

On 23/03/2016 02:07, rahulmutt@gmail.com wrote:

Hi John,

ghc-prim is just a stub package generated for the purpose of documentation. All primops are defined in a low level language called Cmm in GHC. If you want to make it even faster, you'll need to learn Cmm and update the definition in GHC. If you want to a specialized implementation for x86 systems, you may need to modify the NCG (Native Code Generator) which requires a knowledge of assembly language.

Hope that helps!

Rahul Muttineni

Sent from my BlackBerry 10 smartphone.

From: John Ky Sent: Wednesday 23 March 2016 4:40 AM To: The Haskell-Beginners Mailing List - Discussion of primarily beginner-level topics related to Haskell Reply To: The Haskell-Beginners Mailing List - Discussion of primarily beginner-level topics related to Haskell Subject: [Haskell-beginners] let x = x in x (GHC.Prim)

Hello Haskellers,

I'm trying to write a faster popCount function for x86 systems.

I tried cloning the ghc-prim package and repurposing it for my own needs, but it isn't working as hoped.

In particular, popCnt64# was implemented in GHC.Prim as:

popCnt64# = let x = x in x

Which shouldn't terminate.  Yet when I call it, it magically finds the C implementation in hs_popcnt64 and returns the correct value.

My cloned project doesn't behave that way.  Instead it doesn't terminate as I would expect.

Anyone know what's happening here, if there is a way to make this work or tell me if I'm going about this completely the wrong way?

Cheers,

-John

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