msvcrt: Import atanh implementation from musl.

configure

@@ -19616,7 +19616,6 @@ $as_echo "#define HAVE_ISNAN 1" >>confdefs.h
 fi
 
 for ac_func in \
-	atanh \
 	exp2 \
 	exp2f \
 	expm1 \

configure.ac

@@ -2656,7 +2656,6 @@ then
 fi
 
 AC_CHECK_FUNCS(\
-	atanh \
 	exp2 \
 	exp2f \
 	expm1 \

dlls/msvcrt/math.c

@@ -6668,21 +6668,38 @@ float CDECL acoshf(float x)
 
 /*********************************************************************
  *      atanh (MSVCR120.@)
+ *
+ * Copied from musl: src/math/atanh.c
  */
 double CDECL atanh(double x)
 {
-    double ret;
+    UINT64 ux = *(UINT64*)&x;
+    int e = ux >> 52 & 0x7ff;
+    int s = ux >> 63;
 
-    if (x > 1 || x < -1) {
+    /* |x| */
+    ux &= (UINT64)-1 / 2;
+    x = *(double*)&ux;
+
+    if (x > 1) {
         *_errno() = EDOM;
-        /* on Linux atanh returns -NAN in this case */
         feraiseexcept(FE_INVALID);
         return NAN;
     }
-    ret = unix_funcs->atanh( x );
 
-    if (!isfinite(ret)) *_errno() = ERANGE;
-    return ret;
+    if (e < 0x3ff - 1) {
+        if (e < 0x3ff - 32) {
+            fp_barrier(x + 0x1p120f);
+            if (e == 0) /* handle underflow */
+                fp_barrier(x * x);
+        } else { /* |x| < 0.5, up to 1.7ulp error */
+            x = 0.5 * log1p(2 * x + 2 * x * x / (1 - x));
+        }
+    } else { /* avoid overflow */
+        x = 0.5 * log1p(2 * (x / (1 - x)));
+        if (isinf(x)) *_errno() = ERANGE;
+    }
+    return s ? -x : x;
 }
 
 /*********************************************************************

dlls/msvcrt/unixlib.c

@@ -43,19 +43,6 @@
 WINE_DEFAULT_DEBUG_CHANNEL(msvcrt);
 
 /*********************************************************************
- *      atanh
- */
-static double CDECL unix_atanh(double x)
-{
-#ifdef HAVE_ATANH
-    return atanh(x);
-#else
-    if (-1e-6 < x && x < 1e-6) return x + x*x*x/3;
-    else return (log(1+x) - log(1-x)) / 2;
-#endif
-}
-
-/*********************************************************************
  *      cosh
  */
 static double CDECL unix_cosh( double x )
@@ -381,7 +368,6 @@ static float CDECL unix_tgammaf(float x)
 
 static const struct unix_funcs funcs =
 {
-    unix_atanh,
     unix_cosh,
     unix_coshf,
     unix_exp,

dlls/msvcrt/unixlib.h

@@ -23,7 +23,6 @@
 
 struct unix_funcs
 {
-    double          (CDECL *atanh)(double x);
     double          (CDECL *cosh)(double x);
     float           (CDECL *coshf)(float x);
     double          (CDECL *exp)(double x);

include/config.h.in

@@ -31,9 +31,6 @@
 /* Define to 1 if you have the <asm/user.h> header file. */
 #undef HAVE_ASM_USER_H
 
-/* Define to 1 if you have the `atanh' function. */
-#undef HAVE_ATANH
-
 /* Define to 1 if you have the <AudioToolbox/AudioConverter.h> header file. */
 #undef HAVE_AUDIOTOOLBOX_AUDIOCONVERTER_H