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| author | Szabolcs Nagy <nsz@port70.net> | 2013-08-15 14:05:19 +0000 |
|---|---|---|
| committer | Szabolcs Nagy <nsz@port70.net> | 2013-08-15 14:05:19 +0000 |
| commit | 6d85096f49fa955e7e1473b7deb30ce55b6c8be0 (patch) | |
| tree | a4254fb4660ce953cdbc2b956a0e6d8fd54d312e /src/math/atan2f.c | |
| parent | 31c5fb80b9eae86f801be4f46025bc6532a554c5 (diff) | |
| download | musl-6d85096f49fa955e7e1473b7deb30ce55b6c8be0.tar.gz musl-6d85096f49fa955e7e1473b7deb30ce55b6c8be0.tar.xz musl-6d85096f49fa955e7e1473b7deb30ce55b6c8be0.zip | |
math: clean up atan2.c
* remove volatile hacks * don't care about inexact flag for now (removed all the +-tiny) * fix atanl to raise underflow properly * remove signed int arithmetics * use pi/2 instead of pi_o_2 (gcc generates the same code, which is not correct, but it does not matter: we mainly care about nearest rounding)
Diffstat (limited to 'src/math/atan2f.c')
| -rw-r--r-- | src/math/atan2f.c | 59 |
1 files changed, 25 insertions, 34 deletions
diff --git a/src/math/atan2f.c b/src/math/atan2f.c index 96839cba..c634d00f 100644 --- a/src/math/atan2f.c +++ b/src/math/atan2f.c @@ -15,72 +15,63 @@ #include "libm.h" -static const volatile float -tiny = 1.0e-30; static const float -pi_o_4 = 7.8539818525e-01, /* 0x3f490fdb */ -pi_o_2 = 1.5707963705e+00, /* 0x3fc90fdb */ -pi = 3.1415927410e+00; /* 0x40490fdb */ -static const volatile float +pi = 3.1415927410e+00, /* 0x40490fdb */ pi_lo = -8.7422776573e-08; /* 0xb3bbbd2e */ float atan2f(float y, float x) { float z; - int32_t k,m,hx,hy,ix,iy; + uint32_t m,ix,iy; - GET_FLOAT_WORD(hx, x); - ix = hx & 0x7fffffff; - GET_FLOAT_WORD(hy, y); - iy = hy & 0x7fffffff; - if (ix > 0x7f800000 || iy > 0x7f800000) /* x or y is NaN */ + if (isnan(x) || isnan(y)) return x+y; - if (hx == 0x3f800000) /* x=1.0 */ + GET_FLOAT_WORD(ix, x); + GET_FLOAT_WORD(iy, y); + if (ix == 0x3f800000) /* x=1.0 */ return atanf(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 &= 0x7fffffff; + iy &= 0x7fffffff; /* when y = 0 */ if (iy == 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 == 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 == 0x7f800000) { if (iy == 0x7f800000) { 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 3.0f*pi_o_4+tiny; /*atan(+INF,-INF)*/ - case 3: return -3.0f*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 0.0f; /* atan(+...,+INF) */ case 1: return -0.0f; /* atan(-...,+INF) */ - case 2: return pi+tiny; /* atan(+...,-INF) */ - case 3: return -pi-tiny; /* atan(-...,-INF) */ + case 2: return pi; /* atan(+...,-INF) */ + case 3: return -pi; /* atan(-...,-INF) */ } } } - /* when y is INF */ - if (iy == 0x7f800000) - return hy < 0 ? -pi_o_2-tiny : pi_o_2+tiny; + /* |y/x| > 0x1p26 */ + if (ix+(26<<23) < iy || iy == 0x7f800000) + return m&1 ? -pi/2 : pi/2; - /* compute y/x */ - k = (iy-ix)>>23; - if (k > 26) { /* |y/x| > 2**26 */ - z = pi_o_2 + 0.5f*pi_lo; - m &= 1; - } else if (k < -26 && hx < 0) /* 0 > |y|/x > -2**-26 */ + /* z = atan(|y/x|) with correct underflow */ + if ((m&2) && iy+(26<<23) < ix) /*|y/x| < 0x1p-26, x < 0 */ z = 0.0; - else /* safe to do y/x */ + else z = atanf(fabsf(y/x)); switch (m) { case 0: return z; /* atan(+,+) */ |