altos: Add floating point math functions from newlib

[fw/altos] / src / math / ef_sqrt.c

diff --git a/src/math/ef_sqrt.c b/src/math/ef_sqrt.c
new file mode 100644 (file)
index 0000000..80e7f36
--- /dev/null
+++ b/src/math/ef_sqrt.c
@@ -0,0 +1,89 @@
+/* ef_sqrtf.c -- float version of e_sqrt.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 "fdlibm.h"
+
+#ifdef __STDC__
+static const float     one     = 1.0, tiny=1.0e-30;
+#else
+static float   one     = 1.0, tiny=1.0e-30;
+#endif
+
+#ifdef __STDC__
+       float __ieee754_sqrtf(float x)
+#else
+       float __ieee754_sqrtf(x)
+       float x;
+#endif
+{
+       float z;
+       __uint32_t r,hx;
+       __int32_t ix,s,q,m,t,i;
+
+       GET_FLOAT_WORD(ix,x);
+       hx = ix&0x7fffffff;
+
+    /* take care of Inf and NaN */
+       if(!FLT_UWORD_IS_FINITE(hx))
+           return x*x+x;               /* sqrt(NaN)=NaN, sqrt(+inf)=+inf
+                                          sqrt(-inf)=sNaN */
+    /* take care of zero and -ves */
+       if(FLT_UWORD_IS_ZERO(hx)) return x;/* sqrt(+-0) = +-0 */
+       if(ix<0) return (x-x)/(x-x);            /* sqrt(-ve) = sNaN */
+
+    /* normalize x */
+       m = (ix>>23);
+       if(FLT_UWORD_IS_SUBNORMAL(hx)) {                /* subnormal x */
+           for(i=0;(ix&0x00800000L)==0;i++) ix<<=1;
+           m -= i-1;
+       }
+       m -= 127;       /* unbias exponent */
+       ix = (ix&0x007fffffL)|0x00800000L;
+       if(m&1) /* odd m, double x to make it even */
+           ix += ix;
+       m >>= 1;        /* m = [m/2] */
+
+    /* generate sqrt(x) bit by bit */
+       ix += ix;
+       q = s = 0;              /* q = sqrt(x) */
+       r = 0x01000000L;                /* r = moving bit from right to left */
+
+       while(r!=0) {
+           t = s+r; 
+           if(t<=ix) { 
+               s    = t+r; 
+               ix  -= t; 
+               q   += r; 
+           } 
+           ix += ix;
+           r>>=1;
+       }
+
+    /* use floating add to find out rounding direction */
+       if(ix!=0) {
+           z = one-tiny; /* trigger inexact flag */
+           if (z>=one) {
+               z = one+tiny;
+               if (z>one)
+                   q += 2;
+               else
+                   q += (q&1);
+           }
+       }
+       ix = (q>>1)+0x3f000000L;
+       ix += (m <<23);
+       SET_FLOAT_WORD(z,ix);
+       return z;
+}