elf.h: add ELFCOMPRESS_ZSTD

[musl] / src / math / atan2.c

diff --git a/src/math/atan2.c b/src/math/atan2.c
index 143c383..5a1903c 100644 (file)
--- a/src/math/atan2.c
+++ b/src/math/atan2.c
@@ -39,74 +39,63 @@
 
 #include "libm.h"
 
-static const volatile double
-tiny  = 1.0e-300;
 static const double
-pi_o_4 = 7.8539816339744827900E-01, /* 0x3FE921FB, 0x54442D18 */
-pi_o_2 = 1.5707963267948965580E+00, /* 0x3FF921FB, 0x54442D18 */
-pi     = 3.1415926535897931160E+00; /* 0x400921FB, 0x54442D18 */
-static const volatile double
+pi     = 3.1415926535897931160E+00, /* 0x400921FB, 0x54442D18 */
 pi_lo  = 1.2246467991473531772E-16; /* 0x3CA1A626, 0x33145C07 */
 
 double atan2(double y, double x)
 {
        double z;
-       int32_t k,m,hx,hy,ix,iy;
-       uint32_t lx,ly;
+       uint32_t m,lx,ly,ix,iy;
 
-       EXTRACT_WORDS(hx, lx, x);
-       ix = hx & 0x7fffffff;
-       EXTRACT_WORDS(hy, ly, y);
-       iy = hy & 0x7fffffff;
-       if ((ix|((lx|-lx)>>31)) > 0x7ff00000 ||
-           (iy|((ly|-ly)>>31)) > 0x7ff00000)  /* x or y is NaN */
+       if (isnan(x) || isnan(y))
                return x+y;
-       if ((hx-0x3ff00000 | lx) == 0)  /* x = 1.0 */
+       EXTRACT_WORDS(ix, lx, x);
+       EXTRACT_WORDS(iy, ly, y);
+       if ((ix-0x3ff00000 | lx) == 0)  /* x = 1.0 */
                return atan(y);
-       m = ((hy>>31)&1) | ((hx>>30)&2);  /* 2*sign(x)+sign(y) */
+       m = ((iy>>31)&1) | ((ix>>30)&2);  /* 2*sign(x)+sign(y) */
+       ix = ix & 0x7fffffff;
+       iy = iy & 0x7fffffff;
 
        /* when y = 0 */
        if ((iy|ly) == 0) {
                switch(m) {
                case 0:
-               case 1: return y;        /* atan(+-0,+anything)=+-0 */
-               case 2: return  pi+tiny; /* atan(+0,-anything) = pi */
-               case 3: return -pi-tiny; /* atan(-0,-anything) =-pi */
+               case 1: return y;   /* atan(+-0,+anything)=+-0 */
+               case 2: return  pi; /* atan(+0,-anything) = pi */
+               case 3: return -pi; /* atan(-0,-anything) =-pi */
                }
        }
        /* when x = 0 */
        if ((ix|lx) == 0)
-               return hy < 0 ? -pi_o_2-tiny : pi_o_2+tiny;
+               return m&1 ? -pi/2 : pi/2;
        /* when x is INF */
        if (ix == 0x7ff00000) {
                if (iy == 0x7ff00000) {
                        switch(m) {
-                       case 0: return  pi_o_4+tiny; /* atan(+INF,+INF) */
-                       case 1: return -pi_o_4-tiny; /* atan(-INF,+INF) */
-                       case 2: return  3.0*pi_o_4+tiny; /* atan(+INF,-INF) */
-                       case 3: return -3.0*pi_o_4-tiny; /* atan(-INF,-INF) */
+                       case 0: return  pi/4;   /* atan(+INF,+INF) */
+                       case 1: return -pi/4;   /* atan(-INF,+INF) */
+                       case 2: return  3*pi/4; /* atan(+INF,-INF) */
+                       case 3: return -3*pi/4; /* atan(-INF,-INF) */
                        }
                } else {
                        switch(m) {
-                       case 0: return  0.0;     /* atan(+...,+INF) */
-                       case 1: return -0.0;     /* atan(-...,+INF) */
-                       case 2: return  pi+tiny; /* atan(+...,-INF) */
-                       case 3: return -pi-tiny; /* atan(-...,-INF) */
+                       case 0: return  0.0; /* atan(+...,+INF) */
+                       case 1: return -0.0; /* atan(-...,+INF) */
+                       case 2: return  pi;  /* atan(+...,-INF) */
+                       case 3: return -pi;  /* atan(-...,-INF) */
                        }
                }
        }
-       /* when y is INF */
-       if (iy == 0x7ff00000)
-               return hy < 0 ? -pi_o_2-tiny : pi_o_2+tiny;
+       /* |y/x| > 0x1p64 */
+       if (ix+(64<<20) < iy || iy == 0x7ff00000)
+               return m&1 ? -pi/2 : pi/2;
 
-       /* compute y/x */
-       k = (iy-ix)>>20;
-       if (k > 60) {                  /* |y/x| >  2**60 */
-               z = pi_o_2+0.5*pi_lo;
-               m &= 1;
-       } else if (hx < 0 && k < -60)  /* 0 > |y|/x > -2**-60 */
-               z = 0.0;
-       else                           /* safe to do y/x */
+       /* z = atan(|y/x|) without spurious underflow */
+       if ((m&2) && iy+(64<<20) < ix)  /* |y/x| < 0x1p-64, x<0 */
+               z = 0;
+       else
                z = atan(fabs(y/x));
        switch (m) {
        case 0: return z;              /* atan(+,+) */