🚀 go-pugleaf

jwromei@cs.vu.nl (Romein JW) writes:

>I wrote a function 

>>>> #if defined __GNUC__ && defined mc68000
>>>> 
>>>> inline static double sin(double angle)
>>>> {
>>>>     double result;
>>>>     asm ("fsinx %1,%0" : "=f" (result) : "f" (angle));
>>>>     return result;
>>>> }
>>>>
>>>> #endif

>and I understand what it is doing, but how should I replace the asm line
>so that it works on a i486 or i386 with FPU ?  I could not find any example
>that used the floating point stack in the documentation.

You have to go into the config directory, and search things like i386.c
and i386.h for the meaning of registers.

I believe that t was the register name for top of stack, and something
was there for the next element (say u for under, but this is possibly wrong).
so the above would be something like
   asm("fsin" : "=t" (result) : "0" (angle))
iff the fsin takes top and delivers top.
Note however, that there is NO WAY to specify a floating variable with
10 bytes of precision, so I do not know whether the above will have
coproc accuracy or not. A pity.