Assembler Function in VC++

Hi !

I am a programming assembler beginner and i have never implemented an Assembler program in VC++.
Recently i found a program which i assume to be an assembler function. I'd like to test this function in VC++ but i absolutly don't know how to use an assembler code in VC++. It would be great if somebody would show me a way to make this prog run in VC++.
Thank you ! :confused:

code:

--------------------------------------------------------------------------------------------------------------

;extern "C" long double _cdecl exp (double x)
_asm
{
_exp PROC NEAR
PUBLIC _exp
FLDL2E
FLD QWORD PTR ; x
FMUL ; z = x*log2(e)
FIST DWORD PTR ; round(z)
SUB ESP, 12
MOV DWORD PTR , 0
MOV DWORD PTR , 80000000H
FISUB DWORD PTR ; z - round(z)
MOV EAX,
ADD EAX,3FFFH
MOV ,EAX
JLE SHORT UNDERFLOW
CMP EAX,8000H
JGE SHORT OVERFLOW
F2XM1
FLD1
FADD ; 2^(z-round(z))
FLD TBYTE PTR ; 2^(round(z))
ADD ESP,12
FMUL ; 2^z = e^x
RET

UNDERFLOW:
FSTP ST
FLDZ ; return 0
ADD ESP,12
RET

OVERFLOW:
PUSH 07F800000H ; +infinity
FSTP ST
FLD DWORD PTR ; return infinity
ADD ESP,16
RET

_exp ENDP

-----------------------------------------------------------------------------------------------------------------------------------
:confused:

Posted on 2003-05-02 05:03:26 by jack37a

Try this.

[size=12]__declspec(naked) long double _cdecl exp( double x )

{

    __asm

    {

        fldl2e

        fld qword ptr [esp+4]    // x

        fmul                     // z = x*log2(e)

        fist dword ptr [esp+4]   // round(z)

        sub esp, 12

        mov dword ptr [esp], 0

        mov dword ptr [esp+4], 0x80000000

        fisub dword ptr [esp+16] // z - round(z)

        mov eax, [esp+16]

        add eax, 0x3fff

        mov [esp+8], eax

        jle UNDERFLOW

        cmp eax, 0x8000

        jge OVERFLOW

        f2xm1

        fld1

        fadd                     // 2^(z-round(z))

        fld tbyte ptr [esp]      // 2^(round(z))

        add esp, 12

        fmul                     // 2^z = e^x

        ret



    UNDERFLOW:

        fstp st

        fldz                     // return 0

        add esp, 12 

        ret



    OVERFLOW:

        push 0x7F800000          // +infinity

        fstp st

        fld dword ptr [esp]      // return infinity

        add esp, 16

        ret

    }

}[/size]

Posted on 2003-05-02 09:59:37 by iblis

Assembler Function in VC++

HI !

thanks, i tried that and the compiler complains about dword and qword. Maybe I have to include some windows header files but which one. Does anybody have an assembler VC++ tutorial for me ?

Posted on 2003-05-02 16:32:46 by jack37a

Assembler Function in VC++

The Function works in VC++ but the inline compiler complains about

error C2400: Inline-Assembler: Syntaxfehler in 'Erster Operand'; 'constant' gefunden

JLE SHORT UNDERFLOW

error C2400: Inline-Assembler: Syntaxfehler in 'Erster Operand'; 'constant' gefunden

JGE SHORT OVERFLOW

error C2400: Inline-Assembler: Syntaxfehler in 'Opcode'; 'constant' gefunden

UNDERFLOW:
FSTP ST
FLDZ //; return 0
ADD ESP,12
RET

error C2400: Inline-Assembler: Syntaxfehler in 'Opcode'; 'constant' gefunden

OVERFLOW:
PUSH 07F800000H //; +infinity
FSTP ST
FLD DWORD PTR //; return infinity
ADD ESP,16
RET

Who can help me ?

Posted on 2003-05-06 17:55:08 by jack37a

Assembler Function in VC++

what vc++ version are you using?

Posted on 2003-05-06 19:57:15 by arkane

Assembler Function in VC++

I tried it and it compiled fine.

Posted on 2003-05-06 22:46:47 by iblis

Assembler Function in VC++

Thanks to all !

It works ! And the function is extremly fast ....
My mistake was that i had a second function and i had included MATH.h in my program.
Without Math.h it compiled fine .....

Thanks again !

Posted on 2003-05-07 05:30:42 by jack37a

Assembler Function in VC++

Hi !

Can I export this function as an C Objectfile (*.obj) or is an assembler function C++ specific.
If it is possibe, how do I do it ?

Thanks !

Posted on 2003-05-09 04:37:26 by jack37a

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