softfloat: pass float_status pointer to pickNaN

Pass float_status structure pointer to the pickNaN so that
machine-specific settings are available to NaN selection code.
Add use_first_nan property to float_status and use it in Xtensa-specific
pickNaN.

Cc: Peter Maydell <peter.maydell@linaro.org>
Cc: "Alex Bennée" <alex.bennee@linaro.org>
Reviewed-by: Alex Bennée <alex.bennee@linaro.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Signed-off-by: Max Filippov <jcmvbkbc@gmail.com>

fpu/softfloat-specialize.c.inc

@@ -380,7 +380,7 @@ static float32 commonNaNToFloat32(commonNaNT a, float_status *status)
 *----------------------------------------------------------------------------*/
 
 static int pickNaN(FloatClass a_cls, FloatClass b_cls,
-                   bool aIsLargerSignificand)
+                   bool aIsLargerSignificand, float_status *status)
 {
 #if defined(TARGET_ARM) || defined(TARGET_MIPS) || defined(TARGET_HPPA)
     /* ARM mandated NaN propagation rules (see FPProcessNaNs()), take
@@ -413,7 +413,7 @@ static int pickNaN(FloatClass a_cls, FloatClass b_cls,
     } else {
         return 1;
     }
-#elif defined(TARGET_PPC) || defined(TARGET_XTENSA) || defined(TARGET_M68K)
+#elif defined(TARGET_PPC) || defined(TARGET_M68K)
     /* PowerPC propagation rules:
      *  1. A if it sNaN or qNaN
      *  2. B if it sNaN or qNaN
@@ -438,6 +438,24 @@ static int pickNaN(FloatClass a_cls, FloatClass b_cls,
     } else {
         return 1;
     }
+#elif defined(TARGET_XTENSA)
+    /*
+     * Xtensa has two NaN propagation modes.
+     * Which one is active is controlled by float_status::use_first_nan.
+     */
+    if (status->use_first_nan) {
+        if (is_nan(a_cls)) {
+            return 0;
+        } else {
+            return 1;
+        }
+    } else {
+        if (is_nan(b_cls)) {
+            return 1;
+        } else {
+            return 0;
+        }
+    }
 #else
     /* This implements x87 NaN propagation rules:
      * SNaN + QNaN => return the QNaN
@@ -625,7 +643,7 @@ static float32 propagateFloat32NaN(float32 a, float32 b, float_status *status)
         aIsLargerSignificand = (av < bv) ? 1 : 0;
     }
 
-    if (pickNaN(a_cls, b_cls, aIsLargerSignificand)) {
+    if (pickNaN(a_cls, b_cls, aIsLargerSignificand, status)) {
         if (is_snan(b_cls)) {
             return float32_silence_nan(b, status);
         }
@@ -763,7 +781,7 @@ static float64 propagateFloat64NaN(float64 a, float64 b, float_status *status)
         aIsLargerSignificand = (av < bv) ? 1 : 0;
     }
 
-    if (pickNaN(a_cls, b_cls, aIsLargerSignificand)) {
+    if (pickNaN(a_cls, b_cls, aIsLargerSignificand, status)) {
         if (is_snan(b_cls)) {
             return float64_silence_nan(b, status);
         }
@@ -927,7 +945,7 @@ floatx80 propagateFloatx80NaN(floatx80 a, floatx80 b, float_status *status)
         aIsLargerSignificand = (a.high < b.high) ? 1 : 0;
     }
 
-    if (pickNaN(a_cls, b_cls, aIsLargerSignificand)) {
+    if (pickNaN(a_cls, b_cls, aIsLargerSignificand, status)) {
         if (is_snan(b_cls)) {
             return floatx80_silence_nan(b, status);
         }
@@ -1075,7 +1093,7 @@ static float128 propagateFloat128NaN(float128 a, float128 b,
         aIsLargerSignificand = (a.high < b.high) ? 1 : 0;
     }
 
-    if (pickNaN(a_cls, b_cls, aIsLargerSignificand)) {
+    if (pickNaN(a_cls, b_cls, aIsLargerSignificand, status)) {
         if (is_snan(b_cls)) {
             return float128_silence_nan(b, status);
         }

fpu/softfloat.c

@@ -881,7 +881,7 @@ static FloatParts pick_nan(FloatParts a, FloatParts b, float_status *s)
     } else {
         if (pickNaN(a.cls, b.cls,
                     a.frac > b.frac ||
-                    (a.frac == b.frac && a.sign < b.sign))) {
+                    (a.frac == b.frac && a.sign < b.sign), s)) {
             a = b;
         }
         if (is_snan(a.cls)) {

include/fpu/softfloat-helpers.h

@@ -95,6 +95,11 @@ static inline void set_snan_bit_is_one(bool val, float_status *status)
     status->snan_bit_is_one = val;
 }
 
+static inline void set_use_first_nan(bool val, float_status *status)
+{
+    status->use_first_nan = val;
+}
+
 static inline void set_no_signaling_nans(bool val, float_status *status)
 {
     status->no_signaling_nans = val;

include/fpu/softfloat-types.h

@@ -171,6 +171,7 @@ typedef struct float_status {
      * softfloat-specialize.inc.c)
      */
     bool snan_bit_is_one;
+    bool use_first_nan;
     bool no_signaling_nans;
 } float_status;