+/* The algorithm that must be used to calculate the estimate
+ * is specified by the ARM ARM.
+ */
+static float64 recip_estimate(float64 a, CPUState *env)
+{
+ float_status *s = &env->vfp.standard_fp_status;
+ /* q = (int)(a * 512.0) */
+ float64 q = float64_mul(float64_512, a, s);
+ int64_t q_int = float64_to_int64_round_to_zero(q, s);
+
+ /* r = 1.0 / (((double)q + 0.5) / 512.0) */
+ q = int64_to_float64(q_int, s);
+ q = float64_add(q, float64_half, s);
+ q = float64_div(q, float64_512, s);
+ q = float64_div(float64_one, q, s);
+
+ /* s = (int)(256.0 * r + 0.5) */
+ q = float64_mul(q, float64_256, s);
+ q = float64_add(q, float64_half, s);
+ q_int = float64_to_int64_round_to_zero(q, s);
+
+ /* return (double)s / 256.0 */
+ return float64_div(int64_to_float64(q_int, s), float64_256, s);
+}
+