newlib-cygwin/winsup/mingw/mingwex/math/acosf.c

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/*
* Written by J.T. Conklin <jtc@netbsd.org>.
* Public domain.
*/
#include <math.h>
float
acosf (float x)
{
float res;
/* acosl = atanl (sqrtl(1 - x^2) / x) */
asm ( "fld %%st\n\t"
"fmul %%st(0)\n\t" /* x^2 */
"fld1\n\t"
"fsubp\n\t" /* 1 - x^2 */
"fsqrt\n\t" /* sqrtl (1 - x^2) */
"fxch %%st(1)\n\t"
"fpatan"
: "=t" (res) : "0" (x) : "st(1)");
return res;
}