libm/math: Update atanh FE_INEXACT code

Replace the code that is there to generate FE_INEXACT with __math_inexact.

Author: futog

newlib/libm/math/s_atanh.c

@@ -34,9 +34,7 @@
 
 #ifdef _NEED_FLOAT64
 
-static const __float64 one = _F_64(1.0), huge = _F_64(1e300);
-
-static const __float64 zero = _F_64(0.0);
+static const __float64 one = _F_64(1.0);
 
 __float64
 atanh64(__float64 x)
@@ -50,8 +48,8 @@ atanh64(__float64 x)
         return __math_invalid(x);
     if (ix == 0x3ff00000)
         return __math_divzero(x < 0);
-    if (ix < 0x3e300000 && (huge + x) > zero)
-        return x; /* x<2**-28 */
+    if (ix < 0x3e300000) /* x<2**-28 */
+        return __math_inexact64(x);
     SET_HIGH_WORD(x, ix);
     if (ix < 0x3fe00000) { /* x < 0.5 */
         t = x + x;

newlib/libm/math/sf_atanh.c

@@ -16,9 +16,7 @@
 
 #include "fdlibm.h"
 
-static const float one = 1.0, huge = 1e30;
-
-static const float zero = 0.0;
+static const float one = 1.0;
 
 float
 atanhf(float x)
@@ -31,8 +29,8 @@ atanhf(float x)
         return __math_invalidf(x);
     if (ix == 0x3f800000)
         return __math_divzerof(x < 0);
-    if (ix < 0x31800000 && (huge + x) > zero)
-        return x; /* x<2**-28 */
+    if (ix < 0x31800000) /* x<2**-28 */
+        return __math_inexactf(x);
     SET_FLOAT_WORD(x, ix);
     if (ix < 0x3f000000) { /* x < 0.5 */
         t = x + x;