softfloat: Convert float128_silence_nan to parts

This is the minimal change that also introduces float128_params,
float128_unpack_raw, and float128_pack_raw without running into
unused symbol Werrors.

Reviewed-by: Alex Bennée <alex.bennee@linaro.org>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
diff --git a/fpu/softfloat-specialize.c.inc b/fpu/softfloat-specialize.c.inc
index 4038955..5b85b84 100644
--- a/fpu/softfloat-specialize.c.inc
+++ b/fpu/softfloat-specialize.c.inc
@@ -197,6 +197,12 @@
     p->cls = float_class_qnan;
 }
 
+static void parts128_silence_nan(FloatParts128 *p, float_status *status)
+{
+    p->frac_hi = parts_silence_nan_frac(p->frac_hi, status);
+    p->cls = float_class_qnan;
+}
+
 /*----------------------------------------------------------------------------
 | The pattern for a default generated extended double-precision NaN.
 *----------------------------------------------------------------------------*/
@@ -1063,25 +1069,6 @@
 }
 
 /*----------------------------------------------------------------------------
-| Returns a quiet NaN from a signalling NaN for the quadruple-precision
-| floating point value `a'.
-*----------------------------------------------------------------------------*/
-
-float128 float128_silence_nan(float128 a, float_status *status)
-{
-    if (no_signaling_nans(status)) {
-        g_assert_not_reached();
-    } else {
-        if (snan_bit_is_one(status)) {
-            return float128_default_nan(status);
-        } else {
-            a.high |= UINT64_C(0x0000800000000000);
-            return a;
-        }
-    }
-}
-
-/*----------------------------------------------------------------------------
 | Returns the result of converting the quadruple-precision floating-point NaN
 | `a' to the canonical NaN format.  If `a' is a signaling NaN, the invalid
 | exception is raised.