[Haskell-cafe] Building Haskell Platform natively for 64bit Windows

Andrew Coppin andrewcoppin at btinternet.com
Thu Jun 9 23:06:34 CEST 2011

On 09/06/2011 08:44 PM, austin seipp wrote:
> On Thu, Jun 9, 2011 at 1:53 PM, Andrew Coppin
> <andrewcoppin at btinternet.com>  wrote:
>> I'm still left wondering if using 32-bit instructions to manipulate 64-bit
>> values is actually that much slower.
> The problem is you're probably going to need to spill things
> (somewhere) in order to operate on the upper 32bits of any given
> register in the non trivial case. x86 already is pathetic in its 8 GP
> registers. amd64 brings it up to 16.

Well, that's true enough.

Given that AMD64 adds more registers, I'm surprised that this apparently 
makes such a small difference to wall-clock run-times. (But perhaps it 
makes a bigger difference for GHC. I don't know.)

>> I'm wondering if you could write the operations you want is small C stub
>> functions, and FFI to them and do it that way. I don't really know enough
>> about this sort of thing to know whether that'll work...
> It's highly unlikely that the cost of a foreign call (even an unsafe
> one) in terms of just CPU cycles will be cheaper than executing a few
> primitive arithmetic ops on the CPU.

Yeah, you're probably right there actually.

Too bad GHC doesn't support inline assembly yet... (Or does it? I know 
it supports inline Core now.)

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