math: nextafter and nexttoward cleanup

[musl] / src / math / nextafter.c

diff --git a/src/math/nextafter.c b/src/math/nextafter.c
index 5e53654..d9e2923 100644 (file)
--- a/src/math/nextafter.c
+++ b/src/math/nextafter.c
@@ -1,79 +1,36 @@
-/* origin: FreeBSD /usr/src/lib/msun/src/s_nextafter.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.
- * ====================================================
- */
-/* IEEE functions
- *      nextafter(x,y)
- *      return the next machine floating-point number of x in the
- *      direction toward y.
- *   Special cases:
- */
-
 #include "libm.h"
 
+#define SIGN ((uint64_t)1<<63)
+
 double nextafter(double x, double y)
 {
-       volatile double t;
-       int32_t hx,hy,ix,iy;
-       uint32_t lx,ly;
-
-       EXTRACT_WORDS(hx, lx, x);
-       EXTRACT_WORDS(hy, ly, y);
-       ix = hx & 0x7fffffff;  /* |x| */
-       iy = hy & 0x7fffffff;  /* |y| */
+       union dshape ux, uy;
+       uint64_t ax, ay;
+       int e;
 
-       if ((ix >= 0x7ff00000 && (ix-0x7ff00000)|lx) != 0 ||   /* x is nan */
-           (iy >= 0x7ff00000 && (iy-0x7ff00000)|ly) != 0)     /* y is nan */
-               return x+y;
-       if (x == y)          /* x == y */
+       if (isnan(x) || isnan(y))
+               return x + y;
+       ux.value = x;
+       uy.value = y;
+       if (ux.bits == uy.bits)
                return y;
-       if ((ix|lx) == 0) {  /* x == 0 */
-               INSERT_WORDS(x, hy&0x80000000, 1);  /* return +-minsubnormal */
-               /* raise underflow flag */
-               t = x*x;
-               if (t == x)
-                       return t;
-               return x;
-       }
-       if (hx >= 0) {  /* x > 0 */
-               if (hx > hy || (hx == hy && lx > ly)) {  /* x > y, x -= ulp */
-                       if (lx == 0)
-                               hx--;
-                       lx--;
-               } else {                                 /* x < y, x += ulp */
-                       lx++;
-                       if (lx == 0)
-                               hx++;
-               }
-       } else {        /* x < 0 */
-               if (hy >= 0 || hx > hy || (hx == hy && lx > ly)) { /* x < y, x -= ulp */
-                       if (lx == 0)
-                               hx--;
-                       lx--;
-               } else {                                 /* x > y, x += ulp */
-                       lx++;
-                       if (lx == 0)
-                               hx++;
-               }
-       }
-       hy = hx & 0x7ff00000;
-       if (hy >= 0x7ff00000)  /* overflow  */
-               return x+x;
-       if (hy < 0x00100000) { /* underflow */
-               /* raise underflow flag */
-               t = x*x;
-               if (t != x) {
-                       INSERT_WORDS(y, hx, lx);
+       ax = ux.bits & ~SIGN;
+       ay = uy.bits & ~SIGN;
+       if (ax == 0) {
+               if (ay == 0)
                        return y;
-               }
+               ux.bits = (uy.bits & SIGN) | 1;
+       } else if (ax > ay || ((ux.bits ^ uy.bits) & SIGN))
+               ux.bits--;
+       else
+               ux.bits++;
+       e = ux.bits >> 52 & 0x7ff;
+       /* raise overflow if ux.value is infinite and x is finite */
+       if (e == 0x7ff)
+               return x + x;
+       /* raise underflow if ux.value is subnormal or zero */
+       if (e == 0) {
+               volatile double z = x*x + ux.value*ux.value;
        }
-       INSERT_WORDS(x, hx, lx);
-       return x;
+       return ux.value;
 }