forked from KolibriOS/kolibrios
68 lines
2.1 KiB
C
68 lines
2.1 KiB
C
|
/* examples for interoperability with assembler
|
||
|
|
|
||
|
|
1. Calling assembler code from .c : see in libc\math any .asm file
|
||
|
|
2. Using inline assembler: see \include\kos32sys1.h and libc\math\fmod.c
|
||
|
|
- https://gcc.gnu.org/onlinedocs/gcc-4.8.5/gcc/Extended-Asm.html
|
||
|
|
- not all constraints from gcc are supported, no "f" or "t" for example
|
||
|
|
- not supported clobberring st registers, must manual add "fstp %%st" at end or similar
|
||
|
|
- need full suffixes for opcodes, fstpl but not fstp
|
||
|
|
|
||
|
|
3. Calling c functions from .asm: see \libc\start\start.asm:99
|
||
|
|
Remember:
|
||
|
|
- small ints always passed as int32, floating point params as 64-bit
|
||
|
|
- returned structs passed on stack with additional hidden 1st param
|
||
|
|
- c functions can use EAX, ECX, EDX without warnings
|
||
|
|
- .c default is cdecl calling convention https://en.wikipedia.org/wiki/X86_calling_conventions
|
||
|
|
- dont use fastcall calling convention, tinycc realized it non-conformant way
|
||
|
|
- tinycc supports only ELF object files
|
||
|
|
|
||
|
|
tcc can be used as a linker
|
||
|
|
*/
|
||
|
|
|
||
|
|
|
||
|
|
|
||
|
|
|
||
|
|
#include <stdio.h>
|
||
|
|
#include <math.h>
|
||
|
|
|
||
|
|
|
||
|
|
main()
|
||
|
|
{
|
||
|
|
int i;
|
||
|
|
for (i = 0; i < 20; i++)
|
||
|
|
{
|
||
|
|
printf("------------------------------------------------------\n");
|
||
|
|
printf ( "remainder of 5.3 / 2 is %f\n", remainder (5.3,2) );
|
||
|
|
printf ( "remainder of 18.5 / 4.2 is %f\n", remainder (18.5,4.2) );
|
||
|
|
//remainder of 5.3 / 2 is -0.700000
|
||
|
|
//remainder of 18.5 / 4.2 is 1.700000
|
||
|
|
|
||
|
|
printf ( "fmod of 5.3 / 2 is %f\n", fmod (5.3,2) );
|
||
|
|
printf ( "fmod of 18.5 / 4.2 is %f\n", fmod (18.5,4.2) );
|
||
|
|
// fmod of 5.3 / 2 is 1.300000
|
||
|
|
// fmod of 18.5 / 4.2 is 1.700000
|
||
|
|
|
||
|
|
double param, fractpart, intpart, result;
|
||
|
|
int n;
|
||
|
|
|
||
|
|
param = 3.14159265;
|
||
|
|
fractpart = modf (param , &intpart);
|
||
|
|
printf ("%f = %f + %f \n", param, intpart, fractpart);
|
||
|
|
//3.141593 = 3.000000 + 0.141593
|
||
|
|
|
||
|
|
param = 0.95;
|
||
|
|
n = 4;
|
||
|
|
result = ldexp (param , n);
|
||
|
|
printf ("%f * 2^%d = %f\n", param, n, result);
|
||
|
|
//0.950000 * 2^4 = 15.200000
|
||
|
|
|
||
|
|
param = 8.0;
|
||
|
|
result = frexp (param , &n);
|
||
|
|
printf ("%f = %f * 2^%d\n", param, result, n);
|
||
|
|
//8.000000 = 0.500000 * 2^4
|
||
|
|
param = 50;
|
||
|
|
result = frexp (param , &n);
|
||
|
|
printf ("%f = %f * 2^%d\n", param, result, n);
|
||
|
|
|
||
|
|
}
|
||
|
|
}
|