PUSH-ing FPU constant...

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AsmGuru62

Joined: 28 Jan 2004
Posts: 1617
Location: Toronto, Canada

AsmGuru62 16 Mar 2012, 21:13

Hi,

I just tried the following code:

Code:

push 0.15

and it actually worked!! I am blown away!
FASM pushes the DWORD (4 byte FLOAT type) onto stack, which is FPU representation of 0.15.
Is it possible to do the same with the QWORD (8 bytes DOUBLE type)?
I tried few things, like:

Code:

pushq 0.15
push qword 0.15

but these did not work.

Well, even if DOUBLE constants can't be PUSH-ed - I am OK to use DWORDs, but precision may be not the same.

So, anyone knows how to do it with DOUBLEs?

P.S. I love FASM!
Now I do not need to waste data section for FPU constants.
And instruction to access stack is coded in less bytes that access the same in data section.
Very cool!!

16 Mar 2012, 21:13

LocoDelAssembly
Your code has a bug

Joined: 06 May 2005
Posts: 4624
Location: Argentina

LocoDelAssembly 16 Mar 2012, 22:36

Code:

macro pushDouble value*
{
local v
  v = value

  push v shr 32 and $FFFF'FFFF
  push v and $FFFF'FFFF
}

If you want to "overload" the PUSH instruction then you could inspect invoke and the macros it depends on and see you double parameters are implemented (I haven't looked into them when writing the code above so it would be a good idea to do it even if you don't want to "overload" PUSH)

16 Mar 2012, 22:36

revolution
When all else fails, read the source

Joined: 24 Aug 2004
Posts: 20292
Location: In your JS exploiting you and your system

revolution 17 Mar 2012, 01:34

This also works:

Code:

use64
mov rax,2.7182818284590452353602874713527
push rax

17 Mar 2012, 01:34

AsmGuru62

Joined: 28 Jan 2004
Posts: 1617
Location: Toronto, Canada

AsmGuru62 18 Mar 2012, 12:57

Cool!
Thanks.

18 Mar 2012, 12:57

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