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msvcrt: Import acos from musl.

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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 17:11:36 +02:00 committed by Alexandre Julliard
parent d53d42f1ae
commit 8034d4179c
1 changed files with 66 additions and 9 deletions
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75
dlls/msvcrt/math.c
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@ -542,18 +542,75 @@ float CDECL MSVCRT_modff( float x, float *iptr )
/*********************************************************************
* MSVCRT_acos (MSVCRT.@)
*
* Copied from musl: src/math/acos.c
*/
static double acos_R(double z)
{
static const double pS0 = 1.66666666666666657415e-01,
pS1 = -3.25565818622400915405e-01,
pS2 = 2.01212532134862925881e-01,
pS3 = -4.00555345006794114027e-02,
pS4 = 7.91534994289814532176e-04,
pS5 = 3.47933107596021167570e-05,
qS1 = -2.40339491173441421878e+00,
qS2 = 2.02094576023350569471e+00,
qS3 = -6.88283971605453293030e-01,
qS4 = 7.70381505559019352791e-02;
double p, q;
p = z * (pS0 + z * (pS1 + z * (pS2 + z * (pS3 + z * (pS4 + z * pS5)))));
q = 1.0 + z * (qS1 + z * (qS2 + z * (qS3 + z * qS4)));
return p/q;
}
double CDECL MSVCRT_acos( double 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). */
double ret = atan2(sqrt((1 - x) * (1 + x)), x);
if (x < -1.0 || x > 1.0 || !isfinite(x))
return math_error(_DOMAIN, "acos", x, 0, ret);
return ret;
static const double pio2_hi = 1.57079632679489655800e+00,
pio2_lo = 6.12323399573676603587e-17;
double z, w, s, c, df;
unsigned int hx, ix;
ULONGLONG llx;
hx = *(ULONGLONG*)&x >> 32;
ix = hx & 0x7fffffff;
/* |x| >= 1 or nan */
if (ix >= 0x3ff00000) {
unsigned int lx;
lx = *(ULONGLONG*)&x;
if (((ix - 0x3ff00000) | lx) == 0) {
/* acos(1)=0, acos(-1)=pi */
if (hx >> 31)
return 2 * pio2_hi + 7.5231638452626401e-37;
return 0;
}
if (isnan(x)) return x;
return math_error(_DOMAIN, "acos", x, 0, 0 / (x - x));
}
/* |x| < 0.5 */
if (ix < 0x3fe00000) {
if (ix <= 0x3c600000) /* |x| < 2**-57 */
return pio2_hi + 7.5231638452626401e-37;
return pio2_hi - (x - (pio2_lo - x * acos_R(x * x)));
}
/* x < -0.5 */
if (hx >> 31) {
z = (1.0 + x) * 0.5;
s = sqrt(z);
w = acos_R(z) * s - pio2_lo;
return 2 * (pio2_hi - (s + w));
}
/* x > 0.5 */
z = (1.0 - x) * 0.5;
s = sqrt(z);
df = s;
llx = (*(ULONGLONG*)&df >> 32) << 32;
df = *(double*)&llx;
c = (z - df * df) / (s + df);
w = acos_R(z) * s + c;
return 2 * (df + w);
}
/*********************************************************************