flat assembler - [Help] - Saving xmm register

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ctl3d32

Joined: 30 Dec 2009
Posts: 204
Location: Brazil

ctl3d32

Hi Folks!

Need help to save xmm register state. Is it possible?

Something like:

Code:

push xmm3 ;save xmm3 value
stdcall something ;proc something will change xmm3 register value
pop xmm3 ;restore xmm3 value

Thanks in advance,
ctl3d32

10 Jan 2011, 03:09

idle

Joined: 06 Jan 2011
Posts: 359
Location: Ukraine

idle

Code:

movaps [esp] ;if destination aligned
movups [esp] ;if destination !aligned

10 Jan 2011, 07:15

ctl3d32

Joined: 30 Dec 2009
Posts: 204
Location: Brazil

ctl3d32

I can't do this:

Code:

proc LUsolve a,l,u
   locals
            lij dq ?
             i dd ?
             j dd ?
   endl
   mov     [i],1
   mov     [j],1
   stdcall getLij,[a],[l],[u],[i],[j]
   movsd   [lij],xmm0
   stdcall setMatrixElem,[l],[i],[j],lij
endp

Only works if lij is declared at .bss or .data section.

Code:

proc LUsolve a,l,u
   locals
             i dd ?
             j dd ?
   endl
   mov     [i],1
   mov     [j],1
   stdcall getLij,[a],[l],[u],[i],[j]
   movsd   [lij],xmm0
   stdcall setMatrixElem,[l],[i],[j],lij
endp

section '.bss' ...
align 16
lij dq ?

Why?

Thanks

10 Jan 2011, 13:41

revolution
When all else fails, read the source

Joined: 24 Aug 2004
Posts: 17467
Location: In your JS exploiting you and your system

revolution

ctl3d32 wrote:

I can't do this:

Code:

proc LUsolve a,l,u
   locals
            lij dq ?
             i dd ?
             j dd ?
   endl
   mov     [i],1
   mov     [j],1
   stdcall getLij,[a],[l],[u],[i],[j]
   movsd   [lij],xmm0
   stdcall setMatrixElem,[l],[i],[j],lij
endp

Only works if lij is declared at .bss or .data section.

Code:

proc LUsolve a,l,u
   locals
             i dd ?
             j dd ?
   endl
   mov     [i],1
   mov     [j],1
   stdcall getLij,[a],[l],[u],[i],[j]
   movsd   [lij],xmm0
   stdcall setMatrixElem,[l],[i],[j],lij
endp

section '.bss' ...
align 16
lij dq ?

Why?

Thanks

The reason is alignment. Use movupd to store to unaligned locations.

Also you need to use addr lij

Code:

stdcall setMatrixElem,[l],[i],[j],addr lij

12 Jan 2011, 08:13

ctl3d32

Joined: 30 Dec 2009
Posts: 204
Location: Brazil

ctl3d32

Can i make local variables aligned 16 like in .data or .bss section?

Thanks

12 Jan 2011, 11:59

edfed

Joined: 20 Feb 2006
Posts: 4240
Location: 2018

edfed

yes, you can.

with align16 directive.

remember that every instructions and directives are designed to be alone, then, they can be inserted anywhere.

12 Jan 2011, 12:27

revolution
When all else fails, read the source

Joined: 24 Aug 2004
Posts: 17467
Location: In your JS exploiting you and your system

revolution

ctl3d32 wrote:

Can i make local variables aligned 16 like in .data or .bss section?

Thanks

Short answer: No.

Long answer: Yes, but ... it requires extra either 1) extra code at function entry to force stack alignment at runtime, or 2) your whole application must be made stack alignment compliant everywhere.

12 Jan 2011, 13:31

rugxulo

Joined: 09 Aug 2005
Posts: 2341
Location: Usono (aka, USA)

rugxulo

fxsave / fxrstor ??

19 Jan 2011, 22:36

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