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Inline assembler inside a member function.

Started by farmersckn Sep 28, 2000 at 4:35 PM 7 replies 200+ views

Original Post

Sep 28, 2000 at 4:35 PM

I''ve tried to use the inline assembler in the member function of a class, but unless i make a local variable and set it to the value of the member it is an alias of, i can''t use members of classes in the inline assembler. Does anyone know how to get access using the inline assembler? I''ve already thought about using globals and using them as aliases for the members, but that will require a little bit of a speed decrease every time i call the methods. etc. etc. plz help. thanks Yesterday is the past, tomorrow is the future. Today is a gift, that is why we call it the present.

Jumpster

Sep 28, 2000 at 5:03 PM

Here''s the code to my Normalize() method...

    
class pt
{
  double x;
  double y;
  double z;

  void Normalize();
}

void pt::Normalize () 
{
  double l = Length ();
  if (l > 0.0) // can never be negative

  {
    //**************************************************

    // In essence, this is what we are doing...
    // The assembly makes the math faster, about 30%
    // x = x*l;

    // y = y*l;

    // z = z*l;

    l = 1.0 / l;
    _asm
    {
      // x = x * l;

      mov           eax, dword ptr [this]
      fld           qword ptr [eax]
      fmul          qword ptr [l]
      fstp          qword ptr [eax]

      // y = y * l;

      fld           qword ptr [eax+8]
      fmul          qword ptr [l]
      fstp          qword ptr [eax+8]

      // z = z * l;

      fld           qword ptr [eax+16]
      fmul          qword ptr [l]
      fstp          qword ptr [eax+16]
    }
  } 
  else 
  {
    Clear ();
  }
}

Regards,
Jumpster

Semper Fi

farmersckn

Sep 29, 2000 at 7:50 PM

I think i got it. Thanks a lot!
farmersckn

Yesterday is the past, tomorrow is the future. Today is a gift, that is why
we call it the present.

Prosper/LOADED

Sep 29, 2000 at 8:21 PM

Notice that it can be tricky. With inheritance, classe''s data can sometimes begin after the ''this'' pointer. It depends on the compiler i think.

I''m not sur thought...

Shannon Barber

Sep 29, 2000 at 10:01 PM

Can''t you replace this with x?
eax+8 with y?
eax+16 with z?

davepermen

Oct 1, 2000 at 7:41 AM

ive tried your source with the _asm insert. it compiles fine, but when i try to start it, there is a messagebox from vc++, "programm could not be executed"...
what should i do?!

(im asking here because i know you made it yet

)

we wanna play, not watch the pictures

Jumpster

Oct 2, 2000 at 8:55 AM

davepermen - Don't forget, you still need a main()/winmain() function. Without it, the program won't start...

Also, don't forget a Length() and Clear() method. Normalize() uses both.


pt::Clear() {x=y=z=0.0;}
pt::Length() {return sqrt(x*x+y*y+z*z); }

BTW - That's not originally even my code. I got it from Mickey Kowacks book.

Regards,
Jumpster

Semper Fi

Edited by - Jumpster on October 2, 2000 9:58:47 AM

davepermen

Oct 2, 2000 at 12:39 PM

it was none of your tips, im sorry.. it was my fault

trick was, i changed the folder for the exe, so that it wasnt in the release-folder anymore, but let vc++ executeing it from the release-folder anyway... ...i was so stupid..

we wanna play, not watch the pictures

Serge K

Oct 6, 2000 at 1:37 AM

quote:
Original post by farmersckn

I''ve tried to use the inline assembler in the member function of a class, but unless i make a local variable and set it to the value of the member it is an alias of, i can''t use members of classes in the inline assembler. Does anyone know how to get access using the inline assembler?

    

class SomeClass
{
  int m_SomeMemberVariable;

  int InlineFunction( int x )
  {
    // inline functions does not receive "this" in ECX

    __asm  mov edx, this
    __asm  mov eax, x
    __asm  add eax, [edx]this.m_SomeMemberVariable
  }
};

int SomeClass::RegularFunction( int x )
{
  __asm  mov eax, x
  // ECX already contains "this"

  __asm  add eax, [ecx]this.m_SomeMemberVariable
}

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