\frac{x}{1 + \sqrt{x + 1}}\begin{array}{l}
\mathbf{if}\;\frac{x}{1 + \sqrt{x + 1}} \le 1012629.646108792512677609920501708984375:\\
\;\;\;\;\frac{x}{{1}^{3} + {\left(\sqrt{x + 1}\right)}^{3}} \cdot \left(1 \cdot 1 + \left(\sqrt{x + 1} \cdot \sqrt{x + 1} - 1 \cdot \sqrt{x + 1}\right)\right)\\
\mathbf{else}:\\
\;\;\;\;\frac{\sqrt{x}}{\frac{1 + \sqrt{x + 1}}{\sqrt{x}}}\\
\end{array}double f(double x) {
double r93139 = x;
double r93140 = 1.0;
double r93141 = r93139 + r93140;
double r93142 = sqrt(r93141);
double r93143 = r93140 + r93142;
double r93144 = r93139 / r93143;
return r93144;
}
double f(double x) {
double r93145 = x;
double r93146 = 1.0;
double r93147 = r93145 + r93146;
double r93148 = sqrt(r93147);
double r93149 = r93146 + r93148;
double r93150 = r93145 / r93149;
double r93151 = 1012629.6461087925;
bool r93152 = r93150 <= r93151;
double r93153 = 3.0;
double r93154 = pow(r93146, r93153);
double r93155 = pow(r93148, r93153);
double r93156 = r93154 + r93155;
double r93157 = r93145 / r93156;
double r93158 = r93146 * r93146;
double r93159 = r93148 * r93148;
double r93160 = r93146 * r93148;
double r93161 = r93159 - r93160;
double r93162 = r93158 + r93161;
double r93163 = r93157 * r93162;
double r93164 = sqrt(r93145);
double r93165 = r93149 / r93164;
double r93166 = r93164 / r93165;
double r93167 = r93152 ? r93163 : r93166;
return r93167;
}



Bits error versus x
Results
if (/ x (+ 1.0 (sqrt (+ x 1.0)))) < 1012629.6461087925Initial program 0.0
rmApplied flip3-+0.0
Applied associate-/r/0.0
if 1012629.6461087925 < (/ x (+ 1.0 (sqrt (+ x 1.0)))) Initial program 0.5
rmApplied add-sqr-sqrt0.1
Applied associate-/l*0.0
Final simplification0.0
herbie shell --seed 2019209 +o rules:numerics
(FPCore (x)
:name "Numeric.Log:$clog1p from log-domain-0.10.2.1, B"
:precision binary64
(/ x (+ 1 (sqrt (+ x 1)))))