math: rewrite modf.c and clean up modff.c

[musl] / src / math / modf.c

diff --git a/src/math/modf.c b/src/math/modf.c
index cca3b65..de45069 100644 (file)
--- a/src/math/modf.c
+++ b/src/math/modf.c
@@ -1,68 +1,37 @@
-/* origin: FreeBSD /usr/src/lib/msun/src/s_modf.c */
-/*
- * ====================================================
- * 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.
- * ====================================================
- */
-/*
- * modf(double x, double *iptr)
- * return fraction part of x, and return x's integral part in *iptr.
- * Method:
- *      Bit twiddling.
- *
- * Exception:
- *      No exception.
- */
-
-#include "libm.h"
+#include <math.h>
+#include <stdint.h>
 
 double modf(double x, double *iptr)
 {
-       int32_t i0,i1,j0;
-       uint32_t i;
+       union {double x; uint64_t n;} u = {x};
+       uint64_t mask;
+       int e;
 
-       EXTRACT_WORDS(i0, i1, x);
-       j0 = ((i0>>20) & 0x7ff) - 0x3ff; /* exponent of x */
-       if (j0 < 20) {  /* integer part in high x */
-               if (j0 < 0) {  /* |x| < 1 */
-                       INSERT_WORDS(*iptr, i0 & 0x80000000, 0); /* *iptr = +-0 */
-                       return x;
-               }
-               i = 0x000fffff >> j0;
-               if (((i0&i)|i1) == 0) {  /* x is integral */
-                       uint32_t high;
-                       *iptr = x;
-                       GET_HIGH_WORD(high, x);
-                       INSERT_WORDS(x, high & 0x80000000, 0);  /* return +-0 */
-                       return x;
-               }
-               INSERT_WORDS(*iptr, i0&~i, 0);
-               return x - *iptr;
-       } else if (j0 > 51) {  /* no fraction part */
-               uint32_t high;
-               if (j0 == 0x400) {  /* inf/NaN */
-                       *iptr = x;
-                       return 0.0 / x;
-               }
+       e = (int)(u.n>>52 & 0x7ff) - 0x3ff;
+
+       /* no fractional part */
+       if (e >= 52) {
                *iptr = x;
-               GET_HIGH_WORD(high, x);
-               INSERT_WORDS(x, high & 0x80000000, 0);  /* return +-0 */
-               return x;
-       } else {               /* fraction part in low x */
-               i = (uint32_t)0xffffffff >> (j0 - 20);
-               if ((i1&i) == 0) {  /* x is integral */
-                       uint32_t high;
-                       *iptr = x;
-                       GET_HIGH_WORD(high, x);
-                       INSERT_WORDS(x, high & 0x80000000, 0);  /* return +-0 */
+               if (e == 0x400 && u.n<<12 != 0) /* nan */
                        return x;
-               }
-               INSERT_WORDS(*iptr, i0, i1&~i);
-               return x - *iptr;
+               u.n &= (uint64_t)1<<63;
+               return u.x;
+       }
+
+       /* no integral part*/
+       if (e < 0) {
+               u.n &= (uint64_t)1<<63;
+               *iptr = u.x;
+               return x;
+       }
+
+       mask = (uint64_t)-1>>12 >> e;
+       if ((u.n & mask) == 0) {
+               *iptr = x;
+               u.n &= (uint64_t)1<<63;
+               return u.x;
        }
+       u.n &= ~mask;
+       *iptr = u.x;
+       return x - *iptr;
 }