softfloat: Add float*_maybe_silence_nan() functions

Add functions float*_maybe_silence_nan() which ensure that a
value is not a signaling NaN by turning it into a quiet NaN.

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Nathan Froyd <froydnj@codesourcery.com>

2 files changed, 40 insertions, 0 deletions

diff --git a/fpu/softfloat-specialize.h b/fpu/softfloat-specialize.h
index 8e6aceb552..07468786f9 100644
--- a/fpu/softfloat-specialize.h
+++ b/fpu/softfloat-specialize.h
@@ -102,6 +102,25 @@ int float32_is_signaling_nan( float32 a_ )
 }
 
 /*----------------------------------------------------------------------------
+| Returns a quiet NaN if the single-precision floating point value `a' is a
+| signaling NaN; otherwise returns `a'.
+*----------------------------------------------------------------------------*/
+
+float32 float32_maybe_silence_nan( float32 a_ )
+{
+    if (float32_is_signaling_nan(a_)) {
+        uint32_t a = float32_val(a_);
+#if SNAN_BIT_IS_ONE
+        a &= ~(1 << 22);
+#else
+        a |= (1 << 22);
+#endif
+        return make_float32(a);
+    }
+    return a_;
+}
+
+/*----------------------------------------------------------------------------
 | Returns the result of converting the single-precision floating-point NaN
 | `a' to the canonical NaN format.  If `a' is a signaling NaN, the invalid
 | exception is raised.
@@ -234,6 +253,25 @@ int float64_is_signaling_nan( float64 a_ )
 }
 
 /*----------------------------------------------------------------------------
+| Returns a quiet NaN if the double-precision floating point value `a' is a
+| signaling NaN; otherwise returns `a'.
+*----------------------------------------------------------------------------*/
+
+float64 float64_maybe_silence_nan( float64 a_ )
+{
+    if (float64_is_signaling_nan(a_)) {
+        bits64 a = float64_val(a_);
+#if SNAN_BIT_IS_ONE
+        a &= ~LIT64( 0x0008000000000000 );
+#else
+        a |= LIT64( 0x0008000000000000 );
+#endif
+        return make_float64(a);
+    }
+    return a_;
+}
+
+/*----------------------------------------------------------------------------
 | Returns the result of converting the double-precision floating-point NaN
 | `a' to the canonical NaN format.  If `a' is a signaling NaN, the invalid
 | exception is raised.
diff --git a/fpu/softfloat.h b/fpu/softfloat.h
index 9bece80d4d..2e651e2605 100644
--- a/fpu/softfloat.h
+++ b/fpu/softfloat.h
@@ -287,6 +287,7 @@ int float32_compare( float32, float32 STATUS_PARAM );
 int float32_compare_quiet( float32, float32 STATUS_PARAM );
 int float32_is_nan( float32 );
 int float32_is_signaling_nan( float32 );
+float32 float32_maybe_silence_nan( float32 );
 float32 float32_scalbn( float32, int STATUS_PARAM );
 
 INLINE float32 float32_abs(float32 a)
@@ -364,6 +365,7 @@ int float64_compare( float64, float64 STATUS_PARAM );
 int float64_compare_quiet( float64, float64 STATUS_PARAM );
 int float64_is_nan( float64 a );
 int float64_is_signaling_nan( float64 );
+float64 float64_maybe_silence_nan( float64 );
 float64 float64_scalbn( float64, int STATUS_PARAM );
 
 INLINE float64 float64_abs(float64 a)