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

[Andrew Coppin]

On 09/06/2011 06:54 AM, Scott Lawrence wrote:
> On 06/09/2011 01:47 AM, Jason Dagit wrote:
>> Have you checked this by looking at the generated assembly?  I
>> generated some assembly from GHC on windows.  Here is what it looks
>> ilke:
>> http://hpaste.org/47610
>>
>> My assembly-fu is not strong enough to tell if it's using 64bit instructions.
>>
> It would appear to be 32-bit. (pushl instead of pushq&  no instances of
> aligning to 8-byte boundaries)

The general register naming scheme on x86 is:

   AL, AH: 8 bits
   AX: 16 bits
   EAX: 32 bits
   RAX: 64 bits

There's a lot of code there, but from what I can see, it's all operating 
on 32-bit registers. So I'd say this is 32-bit code.

On the other hand, I still think it would be worth actually benchmarking 
this stuff to see how much difference it makes. Wouldn't surprise me if 
the CPU designers did some clever trickery with pipelining and 
superscalar execution to make two adjacent 32-bit instructions execute 
the same way as a single 64-bit instruction would...

(I've seen various sources claim that running software in 64-bit mode 
only gives you a 2% speedup. Then again, they presumably aren't testing 
with chess software which heavily utilises explicit 64-bit operations.)