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msvcrt: Import acosf from musl. 

Signed-off-by: Piotr Caban <piotr@codeweavers.com>
Signed-off-by: Alexandre Julliard <julliard@winehq.org>
This commit is contained in:
Piotr Caban 2020-08-05 17:11:20 +02:00 committed by Alexandre Julliard
parent a518975663
commit d53d42f1ae
1 changed files with 54 additions and 9 deletions
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63
dlls/msvcrt/math.c
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@ -219,18 +219,63 @@ INT CDECL MSVCRT__isnanf( float num )
/*********************************************************************
* MSVCRT_acosf (MSVCRT.@)
*
* Copied from musl: src/math/acosf.c
*/
static float acosf_R(float z)
{
static const float pS0 = 1.6666586697e-01,
pS1 = -4.2743422091e-02,
pS2 = -8.6563630030e-03,
qS1 = -7.0662963390e-01;
float p, q;
p = z * (pS0 + z * (pS1 + z * pS2));
q = 1.0f + z * qS1;
return p / q;
}
float CDECL MSVCRT_acosf( float x )
{
/* glibc implements acos() as the FPU equivalent of atan2(sqrt(1 - x ^ 2), x).
* asin() uses a similar construction. This is bad because as x gets nearer to
* 1 the error in the expression "1 - x^2" can get relatively large due to
* cancellation. The sqrt() makes things worse. A safer way to calculate
* acos() is to use atan2(sqrt((1 - x) * (1 + x)), x). */
float ret = atan2f(sqrtf((1 - x) * (1 + x)), x);
if (x < -1.0 || x > 1.0 || !finitef(x))
return math_error(_DOMAIN, "acosf", x, 0, ret);
return ret;
static const float pio2_hi = 1.5707962513e+00,
pio2_lo = 7.5497894159e-08;
float z, w, s, c, df;
unsigned int hx, ix;
hx = *(unsigned int*)&x;
ix = hx & 0x7fffffff;
/* |x| >= 1 or nan */
if (ix >= 0x3f800000) {
if (ix == 0x3f800000) {
if (hx >> 31)
return 2 * pio2_hi + 7.5231638453e-37;
return 0;
}
if (MSVCRT__isnanf(x)) return x;
return math_error(_DOMAIN, "acosf", x, 0, 0 / (x - x));
}
/* |x| < 0.5 */
if (ix < 0x3f000000) {
if (ix <= 0x32800000) /* |x| < 2**-26 */
return pio2_hi + 7.5231638453e-37;
return pio2_hi - (x - (pio2_lo - x * acosf_R(x * x)));
}
/* x < -0.5 */
if (hx >> 31) {
z = (1 + x) * 0.5f;
s = sqrtf(z);
w = acosf_R(z) * s - pio2_lo;
return 2 * (pio2_hi - (s + w));
}
/* x > 0.5 */
z = (1 - x) * 0.5f;
s = sqrtf(z);
hx = *(unsigned int*)&s & 0xfffff000;
df = *(float*)&hx;
c = (z - df * df) / (s + df);
w = acosf_R(z) * s + c;
return 2 * (df + w);
}
/*********************************************************************