convert 32 int to float in Assembler

Question

I have found this code for converting float to int.

int ftoi(float flt)
{
    int i;
    _asm
    {
        mov  eax,flt; //loaded mem to acc
        rcl  eax,1;   //left shift acc to remove the sign
        mov  ebx,eax; //save the acc
        mov  edx,4278190080; //clear reg edx;
        and  eax,edx; //and acc to retrieve the exponent
        shr  eax,24;
        sub  eax,7fh; //subtract 7fh(127) to get the actual power 
        mov  edx,eax; //save acc val power
        mov  eax,ebx; //retrieve from ebx
        rcl  eax,8;     //trim the left 8 bits that contain the power
        mov  ebx,eax; //store
        mov  ecx, 1fh; //subtract 17 h
        sub  ecx,edx; 
        mov  edx,00000000h;
        cmp  ecx,0;
        je   loop2;
        shr  eax,1;
        or   eax,80000000h;        
loop1:    
        shr  eax,1; //shift (total bits - power bits);
        sub  ecx,1;
        add  edx,1;
        cmp  ecx,0;
        ja   loop1;
loop2:  
        mov  i, eax;        

//check sign +/-        
sign:
        mov  eax,flt;
        and  eax,80000000h;
        cmp  eax,80000000h;
        je     putsign;
    }

    return i;

putsign:
    return -i;
}

Do you think that's possible to edit this piece of code to convert 32 Int to float?

If it is could you give me some advice how to do it?

Thank you very much for all suggestions and answers.

Answer 1

My suggestion:

#include <stdio.h>

float itof (int i)
{
    float flt = 0.0;

    _asm
    {
        mov eax, i
        bt eax, 31
        jnc plus

        rcr [flt], 1
        neg eax

        plus:

        mov edx, 0x7F       // Bias

        bsr ebx, eax

        mov ecx, 23
        cmp ebx, ecx
        jbe fit

        // too big:
        sub bl, cl
        mov cl, bl
        shr eax, cl
        setc cl             // to round or not to round
        add eax, ecx
        add edx, ebx
        mov cl, 23

        fit:
        bsr ebx, eax
        btr eax, ebx
        sub cl, bl
        shl eax, cl
        or [flt], eax

        add ebx, edx
        shl ebx, 23
        or [flt], ebx
    }

    return flt;
}

int main ( void )
{
    float flt;
    int i;

    i = 12345678;
//  i = -0x8888888;     // different results, both are right

    flt = (float)i;
    printf("%i  %f\n",i,flt);

    flt = itof (i);
    printf("%i  %f\n",i,flt);

    return 0;
}