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NASM Forum => Using NASM => Topic started by: nobody on June 02, 2009, 11:58:58 PM

Title: fistp to general purpose reg ?
Post by: nobody on June 02, 2009, 11:58:58 PM

Hi,

i have got a new question, is it possible to pop from the FPU stack and deposit to general purpose register without doing FIST to memory?
Or in other words,, is there any way to do
FISTP RAX
or something equivalent? (i can't write to memory because of low speed)

Title: Re: fistp to general purpose reg ?
Post by: nobody on June 03, 2009, 02:33:13 AM

One would think that there's cache, and your stack would be a primary candidate for being in the processor cache?  if you push, and pop in quick successesion... does it really hit memory, unless you're looking to see if it hit memory?

Title: Re: fistp to general purpose reg ?
Post by: nobody on June 03, 2009, 06:27:36 PM

>does it really hit memory, unless you're
>looking to see if it hit memory?  

yes it will hit memory. I process large data arrays, and i need to use those FPU registers as a storage for calculations i am doing in XMM registers. (to minimize DRAM latency) , so i need to pop from FPU to somewhere inside CPU, because if it goes out, i lost 200 cycles or so.