first commit of the new libm!

[musl] / src / math / __rem_pio2f.c

diff --git a/src/math/__rem_pio2f.c b/src/math/__rem_pio2f.c
new file mode 100644 (file)
index 0000000..965dc46
--- /dev/null
+++ b/src/math/__rem_pio2f.c
@@ -0,0 +1,78 @@
+/* origin: FreeBSD /usr/src/lib/msun/src/e_rem_pio2f.c */
+/*
+ * Conversion to float by Ian Lance Taylor, Cygnus Support, ian@cygnus.com.
+ * Debugged and optimized by Bruce D. Evans.
+ */
+/*
+ * ====================================================
+ * 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.
+ * ====================================================
+ */
+/* __rem_pio2f(x,y)
+ *
+ * return the remainder of x rem pi/2 in *y
+ * use double precision for everything except passing x
+ * use __rem_pio2_large() for large x
+ */
+
+#include "libm.h"
+
+/*
+ * invpio2:  53 bits of 2/pi
+ * pio2_1:   first  33 bit of pi/2
+ * pio2_1t:  pi/2 - pio2_1
+ */
+static const double
+invpio2 = 6.36619772367581382433e-01, /* 0x3FE45F30, 0x6DC9C883 */
+pio2_1  = 1.57079631090164184570e+00, /* 0x3FF921FB, 0x50000000 */
+pio2_1t = 1.58932547735281966916e-08; /* 0x3E5110b4, 0x611A6263 */
+
+int __rem_pio2f(float x, double *y)
+{
+       double w,r,fn;
+       double tx[1],ty[1];
+       float z;
+       int32_t e0,n,ix,hx;
+
+       GET_FLOAT_WORD(hx, x);
+       ix = hx & 0x7fffffff;
+       /* 33+53 bit pi is good enough for medium size */
+       if (ix < 0x4dc90fdb) {  /* |x| ~< 2^28*(pi/2), medium size */
+               /* Use a specialized rint() to get fn.  Assume round-to-nearest. */
+               STRICT_ASSIGN(double, fn, x*invpio2 + 0x1.8p52);
+               fn = fn - 0x1.8p52;
+// FIXME
+#ifdef HAVE_EFFICIENT_IRINT
+               n  = irint(fn);
+#else
+               n  = (int32_t)fn;
+#endif
+               r  = x - fn*pio2_1;
+               w  = fn*pio2_1t;
+               *y = r - w;
+               return n;
+       }
+       /*
+        * all other (large) arguments
+        */
+       if(ix>=0x7f800000) {  /* x is inf or NaN */
+               *y = x-x;
+               return 0;
+       }
+       /* set z = scalbn(|x|,ilogb(|x|)-23) */
+       e0 = (ix>>23) - 150;  /* e0 = ilogb(|x|)-23; */
+       SET_FLOAT_WORD(z, ix - ((int32_t)(e0<<23)));
+       tx[0] = z;
+       n  =  __rem_pio2_large(tx,ty,e0,1,0);
+       if (hx < 0) {
+               *y = -ty[0];
+               return -n;
+       }
+       *y = ty[0];
+       return n;
+}