math: finished cosh.c cleanup

[musl] / src / math / coshl.c

diff --git a/src/math/coshl.c b/src/math/coshl.c
index 3ea56e0..d09070b 100644 (file)
--- a/src/math/coshl.c
+++ b/src/math/coshl.c
@@ -1,35 +1,3 @@
-/* origin: OpenBSD /usr/src/lib/libm/src/ld80/e_coshl.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.
- * ====================================================
- */
-/* coshl(x)
- * Method :
- * mathematically coshl(x) if defined to be (exp(x)+exp(-x))/2
- *      1. Replace x by |x| (coshl(x) = coshl(-x)).
- *      2.
- *                                                      [ exp(x) - 1 ]^2
- *          0        <= x <= ln2/2  :  coshl(x) := 1 + -------------------
- *                                                         2*exp(x)
- *
- *                                                 exp(x) +  1/exp(x)
- *          ln2/2    <= x <= 22     :  coshl(x) := -------------------
- *                                                         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) := inf (overflow)
- *
- * Special cases:
- *      coshl(x) is |x| if x is +INF, -INF, or NaN.
- *      only coshl(0)=1 is exact for finite x.
- */
-
 #include "libm.h"
 
 #if LDBL_MANT_DIG == 53 && LDBL_MAX_EXP == 1024
@@ -45,41 +13,32 @@ long double coshl(long double x)
                struct{uint64_t m; uint16_t se; uint16_t pad;} i;
        } u = {.f = x};
        unsigned ex = u.i.se & 0x7fff;
+       uint32_t w;
        long double t;
-       uint32_t mx,lx;
 
        /* |x| */
        u.i.se = ex;
        x = u.f;
-       mx = u.i.m >> 32;
-       lx = u.i.m;
+       w = u.i.m >> 32;
 
-       /* |x| in [0,0.5*ln2], return 1+expm1l(|x|)^2/(2*expl(|x|)) */
-       if (ex < 0x3fff-2 || (ex == 0x3fff-2 && mx < 0xb17217f7)) {
-               t = expm1l(x);
-               if (ex < 0x3fff-64)
+       /* |x| < log(2) */
+       if (ex < 0x3fff-1 || (ex == 0x3fff-1 && w < 0xb17217f7)) {
+               if (ex < 0x3fff-32) {
+                       FORCE_EVAL(x + 0x1p120f);
                        return 1;
+               }
+               t = expm1l(x);
                return 1 + t*t/(2*(1+t));
        }
 
-       /* |x| in [0.5*ln2,22], return (exp(|x|)+1/exp(|x|)/2; */
-       if (ex < 0x3fff+4 || (ex == 0x3fff+4 && mx < 0xb0000000)) {
+       /* |x| < log(LDBL_MAX) */
+       if (ex < 0x3fff+13 || (ex == 0x3fff+13 && w < 0xb17217f7)) {
                t = expl(x);
-               return 0.5*t + 0.5/t;
-       }
-
-       /* |x| in [22, ln(maxdouble)] return 0.5*exp(|x|) */
-       if (ex < 0x3fff+13 || (ex == 0x3fff+13 && mx < 0xb1700000))
-               return 0.5*expl(x);
-
-       /* |x| in [log(maxdouble), log(2*maxdouble)) */
-       if (ex == 0x3fff+13 && (mx < 0xb174ddc0 ||
-            (mx == 0xb174ddc0 && lx < 0x31aec0eb))) {
-               t = expl(0.5*x);
-               return 0.5*t*t;
+               return 0.5*(t + 1/t);
        }
 
-       /* |x| >= log(2*maxdouble) or nan */
-       return x*0x1p16383L;
+       /* |x| > log(LDBL_MAX) or nan */
+       t = expl(0.5*x);
+       return 0.5*t*t;
 }
 #endif