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Unified Diff: fusl/src/math/atanf.c

Issue 1573973002: Add a "fork" of musl as //fusl. (Closed) Base URL: https://github.com/domokit/mojo.git@master
Patch Set: Created 4 years, 11 months ago
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Index: fusl/src/math/atanf.c
diff --git a/fusl/src/math/atanf.c b/fusl/src/math/atanf.c
new file mode 100644
index 0000000000000000000000000000000000000000..178341b670fa249fa50157d878ac2a66bd7f1843
--- /dev/null
+++ b/fusl/src/math/atanf.c
@@ -0,0 +1,94 @@
+/* origin: FreeBSD /usr/src/lib/msun/src/s_atanf.c */
+/*
+ * Conversion to float by Ian Lance Taylor, Cygnus Support, ian@cygnus.com.
+ */
+/*
+ * ====================================================
+ * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
+ *
+ * Developed at SunPro, a Sun Microsystems, Inc. business.
+ * Permission to use, copy, modify, and distribute this
+ * software is freely granted, provided that this notice
+ * is preserved.
+ * ====================================================
+ */
+
+
+#include "libm.h"
+
+static const float atanhi[] = {
+ 4.6364760399e-01, /* atan(0.5)hi 0x3eed6338 */
+ 7.8539812565e-01, /* atan(1.0)hi 0x3f490fda */
+ 9.8279368877e-01, /* atan(1.5)hi 0x3f7b985e */
+ 1.5707962513e+00, /* atan(inf)hi 0x3fc90fda */
+};
+
+static const float atanlo[] = {
+ 5.0121582440e-09, /* atan(0.5)lo 0x31ac3769 */
+ 3.7748947079e-08, /* atan(1.0)lo 0x33222168 */
+ 3.4473217170e-08, /* atan(1.5)lo 0x33140fb4 */
+ 7.5497894159e-08, /* atan(inf)lo 0x33a22168 */
+};
+
+static const float aT[] = {
+ 3.3333328366e-01,
+ -1.9999158382e-01,
+ 1.4253635705e-01,
+ -1.0648017377e-01,
+ 6.1687607318e-02,
+};
+
+float atanf(float x)
+{
+ float_t w,s1,s2,z;
+ uint32_t ix,sign;
+ int id;
+
+ GET_FLOAT_WORD(ix, x);
+ sign = ix>>31;
+ ix &= 0x7fffffff;
+ if (ix >= 0x4c800000) { /* if |x| >= 2**26 */
+ if (isnan(x))
+ return x;
+ z = atanhi[3] + 0x1p-120f;
+ return sign ? -z : z;
+ }
+ if (ix < 0x3ee00000) { /* |x| < 0.4375 */
+ if (ix < 0x39800000) { /* |x| < 2**-12 */
+ if (ix < 0x00800000)
+ /* raise underflow for subnormal x */
+ FORCE_EVAL(x*x);
+ return x;
+ }
+ id = -1;
+ } else {
+ x = fabsf(x);
+ if (ix < 0x3f980000) { /* |x| < 1.1875 */
+ if (ix < 0x3f300000) { /* 7/16 <= |x| < 11/16 */
+ id = 0;
+ x = (2.0f*x - 1.0f)/(2.0f + x);
+ } else { /* 11/16 <= |x| < 19/16 */
+ id = 1;
+ x = (x - 1.0f)/(x + 1.0f);
+ }
+ } else {
+ if (ix < 0x401c0000) { /* |x| < 2.4375 */
+ id = 2;
+ x = (x - 1.5f)/(1.0f + 1.5f*x);
+ } else { /* 2.4375 <= |x| < 2**26 */
+ id = 3;
+ x = -1.0f/x;
+ }
+ }
+ }
+ /* end of argument reduction */
+ z = x*x;
+ w = z*z;
+ /* break sum from i=0 to 10 aT[i]z**(i+1) into odd and even poly */
+ s1 = z*(aT[0]+w*(aT[2]+w*aT[4]));
+ s2 = w*(aT[1]+w*aT[3]);
+ if (id < 0)
+ return x - x*(s1+s2);
+ z = atanhi[id] - ((x*(s1+s2) - atanlo[id]) - x);
+ return sign ? -z : z;
+}
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