Floating Point examples

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me239

Joined: 06 Jan 2011
Posts: 200

me239 13 Oct 2011, 22:35

Hey guys, I've been looking all over for some SIMPLE examples of floating point math done in assembly and printing it. Preferably 16 bit, thanks!

13 Oct 2011, 22:35

Fred

Joined: 22 Oct 2010
Posts: 39

Fred 14 Oct 2011, 06:25

Floating point math in SSE is very easy to do.

Code:

movd  xmm0,[esp+4] ;move some float from the stack to xmm0[0-31]
movd  xmm1,[esp+8] ;^ but to xmm1[0-31]
addss xmm0,xmm1    ;add scalar single (xmm[0-31] + xmm[0-31])

That's about as simple of an example you'll get Very Happy

I don't think there's any instructions for 16 bit floats... yet. I'm pretty sure some new processor was going to support 32 <-> 16 bit float conversion though.

Printing floats would require some windows calls(if you're on windows anyway) and that's unfortunately not my area of expertise. Razz

14 Oct 2011, 06:25

macgub

Joined: 11 Jan 2006
Posts: 356
Location: Poland

macgub 18 Oct 2011, 10:05

The same code done on FPU:

Code:

fninit
fld     dword[esp+4]   ; single precision, 32 bits.
fadd  dword[esp+8]   ; st0 - result

18 Oct 2011, 10:05

Akujin

Joined: 11 Oct 2011
Posts: 26
Location: Exile

Akujin 18 Oct 2011, 19:25

Internals of FPU and MA$M examples.
http://www.ray.masmcode.com/downloads/SimplyFPU1-6.zip

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18 Oct 2011, 19:25

edfed

Joined: 20 Feb 2006
Posts: 4350
Location: Now

edfed 18 Oct 2011, 21:08

simple example:

compute ebx=eax*1.32456

Code:

example1:
push dword 1.32456 eax ;preload in stack
finit     ;init the fpu
fld [ss:esp+4] ;load float 1.32456
fimul [ss:esp] ;mul by eax value
fistp [ss:esp+4] ;store in second pop
pop eax eax ;pop two times, free the stack
ret ;quit

compute eax=eax*sin(eax*pi)

Code:

example2:
push eax
finit
fldpi ;load pi value
fimul [ss:esp] ;mul by eax
fsin ;sinus of st0 in st0
fimul [ss:esp]
fistp [ss:esp]
pop eax
ret

the fpu is simple in fact.

18 Oct 2011, 21:08

me239

Joined: 06 Jan 2011
Posts: 200

me239 19 Oct 2011, 03:51

edfed wrote:

simple example:

compute ebx=eax*1.32456

Code:

example1:
push dword 1.32456 eax ;preload in stack
finit     ;init the fpu
fld [ss:esp+4] ;load float 1.32456
fimul [ss:esp] ;mul by eax value
fistp [ss:esp+4] ;store in second pop
pop eax eax ;pop two times, free the stack
ret ;quit

compute eax=eax*sin(eax*pi)

Code:

example2:
push eax
finit
fldpi ;load pi value
fimul [ss:esp] ;mul by eax
fsin ;sinus of st0 in st0
fimul [ss:esp]
fistp [ss:esp]
pop eax
ret

the fpu is simple in fact.

now how would I print one of those values to the prompt?

19 Oct 2011, 03:51

emc

Joined: 20 Aug 2011
Posts: 90
Location: France

emc 22 Oct 2011, 06:49

You can use printf with a formatted string (with %f) to print floating values.

22 Oct 2011, 06:49

me239

Joined: 06 Jan 2011
Posts: 200

me239 22 Oct 2011, 23:16

emc wrote:

You can use printf with a formatted string (with %f) to print floating values.

I'm using DOS

22 Oct 2011, 23:16

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