math: nextafter and nexttoward cleanup

[musl] / src / math / nexttoward.c

diff --git a/src/math/nexttoward.c b/src/math/nexttoward.c
index e150eaa..741b6b5 100644 (file)
--- a/src/math/nexttoward.c
+++ b/src/math/nexttoward.c
@@ -1,15 +1,3 @@
-/* origin: FreeBSD /usr/src/lib/msun/src/s_nexttoward.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.
- * ====================================================
- */
-
 #include "libm.h"
 
 #if LDBL_MANT_DIG == 53 && LDBL_MAX_EXP == 1024
@@ -17,52 +5,42 @@ double nexttoward(double x, long double y)
 {
        return nextafter(x, y);
 }
-#elif (LDBL_MANT_DIG == 64 || LDBL_MANT_DIG == 113) && LDBL_MAX_EXP == 16384
+#else
+#define SIGN ((uint64_t)1<<63)
+
 double nexttoward(double x, long double y)
 {
-       union IEEEl2bits uy;
-       volatile double t;
-       int32_t hx,ix;
-       uint32_t lx;
+       union dshape ux;
+       int e;
 
-       EXTRACT_WORDS(hx, lx, x);
-       ix = hx & 0x7fffffff;
-       uy.e = y;
-
-       if ((ix >= 0x7ff00000 && ((ix-0x7ff00000)|lx) != 0) ||
-           (uy.bits.exp == 0x7fff && ((uy.bits.manh&~LDBL_NBIT)|uy.bits.manl) != 0))
-               return x + y;  /* x or y is nan */
+       if (isnan(x) || isnan(y))
+               return x + y;
        if (x == y)
-               return (double)y;
-       if (x == 0.0) {
-               INSERT_WORDS(x, uy.bits.sign<<31, 1);  /* return +-minsubnormal */
-               /* raise underflow */
-               t = x * x;
-               if (t == x)
-                       return t;
-               return x;
-       }
-       if (hx > 0.0 ^ x < y) {  /* x -= ulp */
-               if (lx == 0)
-                       hx--;
-               lx--;
-       } else {                 /* x += ulp */
-               lx++;
-               if (lx == 0)
-                       hx++;
+               return y;
+       ux.value = x;
+       if (x == 0) {
+               ux.bits = 1;
+               if (signbit(y))
+                       ux.bits |= SIGN;
+       } else if (x < y) {
+               if (signbit(x))
+                       ux.bits--;
+               else
+                       ux.bits++;
+       } else {
+               if (signbit(x))
+                       ux.bits++;
+               else
+                       ux.bits--;
        }
-       ix = hx & 0x7ff00000;
-       if (ix >= 0x7ff00000)   /* overflow  */
+       e = ux.bits>>52 & 0x7ff;
+       /* raise overflow if ux.value is infinite and x is finite */
+       if (e == 0x7ff)
                return x + x;
-       if (ix < 0x00100000) {  /* underflow */
-               /* raise underflow flag */
-               t = x * x;
-               if (t != x) {
-                       INSERT_WORDS(x, hx, lx);
-                       return x;
-               }
+       /* raise underflow if ux.value is subnormal or zero */
+       if (e == 0) {
+               volatile float z = x*x + ux.value*ux.value;
        }
-       INSERT_WORDS(x, hx, lx);
-       return x;
+       return ux.value;
 }
 #endif