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