first commit of the new libm!

[musl] / src / math / fmodf.c

diff --git a/src/math/fmodf.c b/src/math/fmodf.c
new file mode 100644 (file)
index 0000000..4b50a3d
--- /dev/null
+++ b/src/math/fmodf.c
@@ -0,0 +1,105 @@
+/* origin: FreeBSD /usr/src/lib/msun/src/e_fmodf.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.
+ * ====================================================
+ */
+/*
+ * fmodf(x,y)
+ * Return x mod y in exact arithmetic
+ * Method: shift and subtract
+ */
+
+#include "libm.h"
+
+static const float one = 1.0, Zero[] = {0.0, -0.0,};
+
+float fmodf(float x, float y)
+{
+       int32_t n,hx,hy,hz,ix,iy,sx,i;
+
+       GET_FLOAT_WORD(hx, x);
+       GET_FLOAT_WORD(hy, y);
+       sx = hx & 0x80000000;  /* sign of x */
+       hx ^= sx;              /* |x| */
+       hy &= 0x7fffffff;      /* |y| */
+
+       /* purge off exception values */
+       if (hy == 0 || hx >= 0x7f800000 ||  /* y=0,or x not finite */
+           hy > 0x7f800000)                /* or y is NaN */
+               return (x*y)/(x*y);
+       if (hx < hy)                        /* |x| < |y| */
+               return x;
+       if (hx == hy)                       /* |x| = |y|, return x*0 */
+               return Zero[(uint32_t)sx>>31];
+
+       /* determine ix = ilogb(x) */
+       if (hx < 0x00800000) {     /* subnormal x */
+               for (ix = -126, i = hx<<8; i > 0; i <<= 1)
+                       ix -= 1;
+       } else
+               ix = (hx>>23) - 127;
+
+       /* determine iy = ilogb(y) */
+       if (hy < 0x00800000) {     /* subnormal y */
+               for (iy = -126, i = hy<<8; i >= 0; i <<= 1)
+                       iy -= 1;
+       } else
+               iy = (hy>>23) - 127;
+
+       /* set up {hx,lx}, {hy,ly} and align y to x */
+       if (ix >= -126)
+               hx = 0x00800000|(0x007fffff&hx);
+       else {          /* subnormal x, shift x to normal */
+               n = -126-ix;
+               hx = hx<<n;
+       }
+       if (iy >= -126)
+               hy = 0x00800000|(0x007fffff&hy);
+       else {          /* subnormal y, shift y to normal */
+               n = -126-iy;
+               hy = hy<<n;
+       }
+
+       /* fix point fmod */
+       n = ix - iy;
+       while (n--) {
+               hz = hx-hy;
+               if (hz<0)
+                       hx = hx+hx;
+               else {
+                       if(hz == 0)   /* return sign(x)*0 */
+                               return Zero[(uint32_t)sx>>31];
+                       hx = hz+hz;
+               }
+       }
+       hz = hx-hy;
+       if (hz >= 0)
+               hx = hz;
+
+       /* convert back to floating value and restore the sign */
+       if (hx == 0)               /* return sign(x)*0 */
+               return Zero[(uint32_t)sx>>31];
+       while (hx < 0x00800000) {  /* normalize x */
+               hx = hx+hx;
+               iy -= 1;
+       }
+       if (iy >= -126) {          /* normalize output */
+               hx = ((hx-0x00800000)|((iy+127)<<23));
+               SET_FLOAT_WORD(x, hx|sx);
+       } else {                   /* subnormal output */
+               n = -126 - iy;
+               hx >>= n;
+               SET_FLOAT_WORD(x, hx|sx);
+               x *= one;          /* create necessary signal */
+       }
+       return x;  /* exact output */
+}