help with inline Assembler

[llueveYescampa]

Hi all,

A couple of years ago, working with OpenWatcom for Windows, I was
able to wrote the inline assembly code shown below. I spent a while
reading and by trail an error I made it work.

I was trying to test the efficiency of the "inner_product()" function
in C++.

Now I am working in Linux and I would like to compile it with g++.

Is the inline assembly of g++ similar?
Can some of this code be reused in g++?

I like to thank all of you in advance for your comments.

Edgar Black

+++++++++++++++++++++++++++++++++++++++++++++++++
double dot_product(double *array1, double *array1End, double *array2)

{

double result;

const unsigned int n = array1End-array1;

_asm {

fldz

mov ecx, n

cmp ecx,0

jz finish

mov esi,array1

mov edi,array2

more:

fld qword ptr [esi]

fmul qword ptr [edi]

faddp st(1),st(0)

add esi,8

add edi,8

loop more

finish:

fstp qword ptr result

} // end asm //

return (result);

} // end of dot_product//
+++++++++++++++++++++++++++++++++++++++++++++++++

[Sebastian Waschik]

Hello,
llueveYescampa <edgar...@gmail.com> writes:

> Hi all,
>
> A couple of years ago, working with OpenWatcom for Windows, I was
> able to wrote the inline assembly code shown below. I spent a while
> reading and by trail an error I made it work.
>
> I was trying to test the efficiency of the "inner_product()" function
> in C++.
>
> Now I am working in Linux and I would like to compile it with g++.
>
> Is the inline assembly of g++ similar?
> Can some of this code be reused in g++?

inline assembler of gcc is different. For example all register are
prefixed by "%". All constants are prefixed by "$".

See: http://www.ibiblio.org/gferg/ldp/GCC-Inline-Assembly-HOWTO.html

Here a simple example
#include <iostream>

int function(void)
{
int result;
asm(
"mov $0x2, %%eax\n\t"
"mov $3, %%ebx\n\t"
"add %%ebx, %%eax\n\t"
"mov %%eax, %0\n\t"
: "=r"(result)
:
: "%eax", "%ebx"
);
return result;
}

int main(void)
{
std::cout << function() << std::endl;
return 0;
}

Viele Grￜￜe
Sebastian Waschik