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.)