Hi Rahul,
I see mention of the popcount instruction in nativeGen/X86/CodeGen.hs. In
particular it looks like it only activates if sse4_2 is activated? Maybe
all I need to do is activate this somehow?
Cheers,
-John
On Wed, 23 Mar 2016 at 12:07
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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