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.)
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