math: cosh cleanup

[musl] / src / math / coshl.c

diff --git a/src/math/coshl.c b/src/math/coshl.c
index 36b52c0..3ea56e0 100644 (file)
--- a/src/math/coshl.c
+++ b/src/math/coshl.c
@@ -23,7 +23,7 @@
  *                                                         2
  *          22       <= x <= lnovft :  coshl(x) := expl(x)/2
  *          lnovft   <= x <= ln2ovft:  coshl(x) := expl(x/2)/2 * expl(x/2)
- *          ln2ovft  <  x           :  coshl(x) := huge*huge (overflow)
+ *          ln2ovft  <  x           :  coshl(x) := inf (overflow)
  *
  * Special cases:
  *      coshl(x) is |x| if x is +INF, -INF, or NaN.
@@ -38,49 +38,48 @@ long double coshl(long double x)
        return cosh(x);
 }
 #elif LDBL_MANT_DIG == 64 && LDBL_MAX_EXP == 16384
-static const long double huge = 1.0e4900L;
-
 long double coshl(long double x)
 {
-       long double t,w;
-       int32_t ex;
+       union {
+               long double f;
+               struct{uint64_t m; uint16_t se; uint16_t pad;} i;
+       } u = {.f = x};
+       unsigned ex = u.i.se & 0x7fff;
+       long double t;
        uint32_t mx,lx;
 
-       /* High word of |x|. */
-       GET_LDOUBLE_WORDS(ex, mx, lx, x);
-       ex &= 0x7fff;
-
-       /* x is INF or NaN */
-       if (ex == 0x7fff) return x*x;
+       /* |x| */
+       u.i.se = ex;
+       x = u.f;
+       mx = u.i.m >> 32;
+       lx = u.i.m;
 
        /* |x| in [0,0.5*ln2], return 1+expm1l(|x|)^2/(2*expl(|x|)) */
-       if (ex < 0x3ffd || (ex == 0x3ffd && mx < 0xb17217f7u)) {
-               t = expm1l(fabsl(x));
-               w = 1.0 + t;
-               if (ex < 0x3fbc) return w;    /* cosh(tiny) = 1 */
-               return 1.0+(t*t)/(w+w);
+       if (ex < 0x3fff-2 || (ex == 0x3fff-2 && mx < 0xb17217f7)) {
+               t = expm1l(x);
+               if (ex < 0x3fff-64)
+                       return 1;
+               return 1 + t*t/(2*(1+t));
        }
 
        /* |x| in [0.5*ln2,22], return (exp(|x|)+1/exp(|x|)/2; */
-       if (ex < 0x4003 || (ex == 0x4003 && mx < 0xb0000000u)) {
-               t = expl(fabsl(x));
+       if (ex < 0x3fff+4 || (ex == 0x3fff+4 && mx < 0xb0000000)) {
+               t = expl(x);
                return 0.5*t + 0.5/t;
        }
 
        /* |x| in [22, ln(maxdouble)] return 0.5*exp(|x|) */
-       if (ex < 0x400c || (ex == 0x400c && mx < 0xb1700000u))
-               return 0.5*expl(fabsl(x));
+       if (ex < 0x3fff+13 || (ex == 0x3fff+13 && mx < 0xb1700000))
+               return 0.5*expl(x);
 
        /* |x| in [log(maxdouble), log(2*maxdouble)) */
-       if (ex == 0x400c && (mx < 0xb174ddc0u ||
-            (mx == 0xb174ddc0u && lx < 0x31aec0ebu)))
-       {
-               w = expl(0.5*fabsl(x));
-               t = 0.5*w;
-               return t*w;
+       if (ex == 0x3fff+13 && (mx < 0xb174ddc0 ||
+            (mx == 0xb174ddc0 && lx < 0x31aec0eb))) {
+               t = expl(0.5*x);
+               return 0.5*t*t;
        }
 
-       /* |x| >= log(2*maxdouble), cosh(x) overflow */
-       return huge*huge;
+       /* |x| >= log(2*maxdouble) or nan */
+       return x*0x1p16383L;
 }
 #endif