Piotr Caban : msvcrt: Import acos from musl.
Alexandre Julliard
julliard at winehq.org
Wed Aug 5 16:05:00 CDT 2020
Module: wine
Branch: master
Commit: 8034d4179c88ae9176ecaae210c30e40084ae29c
URL: https://source.winehq.org/git/wine.git/?a=commit;h=8034d4179c88ae9176ecaae210c30e40084ae29c
Author: Piotr Caban <piotr at codeweavers.com>
Date: Wed Aug 5 17:11:36 2020 +0200
msvcrt: Import acos from musl.
Signed-off-by: Piotr Caban <piotr at codeweavers.com>
Signed-off-by: Alexandre Julliard <julliard at winehq.org>
---
dlls/msvcrt/math.c | 75 +++++++++++++++++++++++++++++++++++++++++++++++-------
1 file changed, 66 insertions(+), 9 deletions(-)
diff --git a/dlls/msvcrt/math.c b/dlls/msvcrt/math.c
index 46af74f09f..06480911af 100644
--- a/dlls/msvcrt/math.c
+++ b/dlls/msvcrt/math.c
@@ -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);
}
/*********************************************************************
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