simple floating point question

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zolkefli

Joined: 05 Mar 2005
Posts: 12

zolkefli 29 Mar 2006, 07:18

I look in FAQ but can find. This is a very simple why.
I try to use 64bit floating point. so I declare

var dq 0.0

then when I try to use the variable like this

MOV qword[var],123.3454

Its error. Where I done wrong.

29 Mar 2006, 07:18

vid
Verbosity in development

Joined: 05 Sep 2003
Posts: 7105
Location: Slovakia

vid 29 Mar 2006, 07:21

there just isn't such instruction. processor doesn't have one.

29 Mar 2006, 07:21

Reverend

Joined: 24 Aug 2004
Posts: 408
Location: Poland

Reverend 29 Mar 2006, 09:17

in 32-bit procedure you can move immediately only one dword. But you can try:

Code:

pushq 123.3454
movq mm0, qword [esp]
movq qword [var], mm0
add esp, 8

; or
pushq 123.3454
fld qword [esp]
fstp qword [var]
add esp, 8

It is also possible to create macro which will convert such mov with qword as operand to two movs.

29 Mar 2006, 09:17

zolkefli

Joined: 05 Mar 2005
Posts: 12

zolkefli 29 Mar 2006, 10:05

thanks

29 Mar 2006, 10:05

zolkefli

Joined: 05 Mar 2005
Posts: 12

zolkefli 29 Mar 2006, 11:27

I try

pushq 123.345

error pushq not valid instruction

29 Mar 2006, 11:27

vid
Verbosity in development

Joined: 05 Sep 2003
Posts: 7105
Location: Slovakia

vid 29 Mar 2006, 13:23

you can use more advanced features:

Code:

macro movq destptr, value
{
   local ..LO, ..HO
   virtual at 0
      dq 123.456
      load ..LO dword from 0
      load ..HO dword from 4
   end virtual
   mov ptr dest, ..LO
   mov ptr dest+4, ..HO
}
dq var
...
movq var, 123.456

(not tested, but idea is there)

29 Mar 2006, 13:23

UCM

Joined: 25 Feb 2005
Posts: 285
Location: Canada

UCM 29 Mar 2006, 21:29

vid wrote:

you can use more advanced features:

Code:

macro movq destptr, value
{
   local ..LO, ..HO
   virtual at 0
      dq 123.456
      load ..LO dword from 0
      load ..HO dword from 4
   end virtual
   mov ptr dest, ..LO
   mov ptr dest+4, ..HO
}
dq var
...
movq var, 123.456

(not tested, but idea is there)

you mean:

Code:

macro movq destptr, value
{
   local ..LO, ..HO
   virtual at 0
      dq value ;not 123.456
      load ..LO dword from 0
      load ..HO dword from 4
   end virtual
   mov [dest], ..LO
   mov [dest+4], ..HO
}
dq var
...
movq var, 123.456

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29 Mar 2006, 21:29

vid
Verbosity in development

Joined: 05 Sep 2003
Posts: 7105
Location: Slovakia

vid 30 Mar 2006, 00:54

yup, that's it. And i think ptr would work too Wink

30 Mar 2006, 00:54

Reverend

Joined: 24 Aug 2004
Posts: 408
Location: Poland

Reverend 30 Mar 2006, 22:03

Yes, that's a great idea, but don't forget that movq is an instruction and your macro overloads it making original one unachievable (eg. movq mm0, qword [esp])

pushq works similar as the movq macro above. I thought it was in official win32ax include, but maybe I'm wrong

30 Mar 2006, 22:03

RedGhost

Joined: 18 May 2005
Posts: 443
Location: BC, Canada

RedGhost 31 Mar 2006, 05:56

Reverend wrote:

Yes, that's a great idea, but don't forget that movq is an instruction and your macro overloads it making original one unachievable (eg. movq mm0, qword [esp])

pushq works similar as the movq macro above. I thought it was in official win32ax include, but maybe I'm wrong

Code:

match pushd =double num,pushd value \{ \local ..high,..low
   virtual at 0
    dq num
    load ..low dword from 0
    load ..high dword from 4
   end virtual
   push ..high
   push ..low
   pushd equ \}

and

Code:

 match pushd =double =ptr var,pushd value \{
   push dword [var+4]
   push dword [var]
   pushd equ \}

are both from win32ax, so you are indeed correct

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31 Mar 2006, 05:56

vid
Verbosity in development

Joined: 05 Sep 2003
Posts: 7105
Location: Slovakia

vid 31 Mar 2006, 07:55

Reverend: you are right, i forgot there is a movq instruction, i don't play with MMX/SSE stuff a lot. This macro should have another name.

31 Mar 2006, 07:55

Reverend

Joined: 24 Aug 2004
Posts: 408
Location: Poland

Reverend 31 Mar 2006, 13:42

zolkefli: According to RedGhost's post and FASM macro, you don't write 'pushq 123.345' but 'push double 123.345' instead.

31 Mar 2006, 13:42

UCM

Joined: 25 Feb 2005
Posts: 285
Location: Canada

UCM 01 Apr 2006, 02:23

or... pushd double 123.345

01 Apr 2006, 02:23

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