target/m68k: implement fatanh

Using a local m68k floatx80_atanh()
[copied from previous:
Written by Andreas Grabher for Previous, NeXT Computer Emulator.]

Signed-off-by: Laurent Vivier <laurent@vivier.eu>
Message-Id: <20180312202728.23790-9-laurent@vivier.eu>

1 files changed, 65 insertions, 0 deletions

diff --git a/target/m68k/softfloat.c b/target/m68k/softfloat.c
index 3d66f6946f..5ce8413e96 100644
--- a/target/m68k/softfloat.c
+++ b/target/m68k/softfloat.c
@@ -2302,3 +2302,68 @@ floatx80 floatx80_acos(floatx80 a, float_status *status)
 
     return a;
 }
+
+/*----------------------------------------------------------------------------
+ | Hyperbolic arc tangent
+ *----------------------------------------------------------------------------*/
+
+floatx80 floatx80_atanh(floatx80 a, float_status *status)
+{
+    flag aSign;
+    int32_t aExp;
+    uint64_t aSig;
+
+    int8_t user_rnd_mode, user_rnd_prec;
+
+    int32_t compact;
+    floatx80 fp0, fp1, fp2, one;
+
+    aSig = extractFloatx80Frac(a);
+    aExp = extractFloatx80Exp(a);
+    aSign = extractFloatx80Sign(a);
+
+    if (aExp == 0x7FFF && (uint64_t) (aSig << 1)) {
+        return propagateFloatx80NaNOneArg(a, status);
+    }
+
+    if (aExp == 0 && aSig == 0) {
+        return packFloatx80(aSign, 0, 0);
+    }
+
+    compact = floatx80_make_compact(aExp, aSig);
+
+    if (compact >= 0x3FFF8000) { /* |X| >= 1 */
+        if (aExp == one_exp && aSig == one_sig) { /* |X| == 1 */
+            float_raise(float_flag_divbyzero, status);
+            return packFloatx80(aSign, floatx80_infinity.high,
+                                floatx80_infinity.low);
+        } else { /* |X| > 1 */
+            float_raise(float_flag_invalid, status);
+            return floatx80_default_nan(status);
+        }
+    } /* |X| < 1 */
+
+    user_rnd_mode = status->float_rounding_mode;
+    user_rnd_prec = status->floatx80_rounding_precision;
+    status->float_rounding_mode = float_round_nearest_even;
+    status->floatx80_rounding_precision = 80;
+
+    one = packFloatx80(0, one_exp, one_sig);
+    fp2 = packFloatx80(aSign, 0x3FFE, one_sig); /* SIGN(X) * (1/2) */
+    fp0 = packFloatx80(0, aExp, aSig); /* Y = |X| */
+    fp1 = packFloatx80(1, aExp, aSig); /* -Y */
+    fp0 = floatx80_add(fp0, fp0, status); /* 2Y */
+    fp1 = floatx80_add(fp1, one, status); /* 1-Y */
+    fp0 = floatx80_div(fp0, fp1, status); /* Z = 2Y/(1-Y) */
+    fp0 = floatx80_lognp1(fp0, status); /* LOG1P(Z) */
+
+    status->float_rounding_mode = user_rnd_mode;
+    status->floatx80_rounding_precision = user_rnd_prec;
+
+    a = floatx80_mul(fp0, fp2,
+                     status); /* ATANH(X) = SIGN(X) * (1/2) * LOG1P(Z) */
+
+    float_raise(float_flag_inexact, status);
+
+    return a;
+}