softfloat: Correctly handle NaNs in float16_to_float32()

Correctly handle NaNs in float16_to_float32(), by defining and
using a float16ToCommonNaN() function, as we do with the other formats.

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Aurelien Jarno <aurelien@aurel32.net>

2 files changed, 18 insertions, 3 deletions

diff --git a/fpu/softfloat-specialize.h b/fpu/softfloat-specialize.h
index 1c0b12b573..2d025bfa36 100644
--- a/fpu/softfloat-specialize.h
+++ b/fpu/softfloat-specialize.h
@@ -120,6 +120,23 @@ float16 float16_maybe_silence_nan(float16 a_)
 }
 
 /*----------------------------------------------------------------------------
+| Returns the result of converting the half-precision floating-point NaN
+| `a' to the canonical NaN format.  If `a' is a signaling NaN, the invalid
+| exception is raised.
+*----------------------------------------------------------------------------*/
+
+static commonNaNT float16ToCommonNaN( float16 a STATUS_PARAM )
+{
+    commonNaNT z;
+
+    if ( float16_is_signaling_nan( a ) ) float_raise( float_flag_invalid STATUS_VAR );
+    z.sign = float16_val(a) >> 15;
+    z.low = 0;
+    z.high = ((bits64) float16_val(a))<<54;
+    return z;
+}
+
+/*----------------------------------------------------------------------------
 | Returns the result of converting the canonical NaN `a' to the half-
 | precision floating-point format.
 *----------------------------------------------------------------------------*/
diff --git a/fpu/softfloat.c b/fpu/softfloat.c
index 80d8cc4894..3abd1708e4 100644
--- a/fpu/softfloat.c
+++ b/fpu/softfloat.c
@@ -2761,9 +2761,7 @@ float32 float16_to_float32(float16 a, flag ieee STATUS_PARAM)
 
     if (aExp == 0x1f && ieee) {
         if (aSig) {
-            /* Make sure correct exceptions are raised.  */
-            float32ToCommonNaN(a STATUS_VAR);
-            aSig |= 0x200;
+            return commonNaNToFloat32(float16ToCommonNaN(a STATUS_VAR) STATUS_VAR);
         }
         return packFloat32(aSign, 0xff, aSig << 13);
     }