target/xtensa: Explicitly set 2-NaN propagation rule

Set the NaN propagation rule explicitly in xtensa_use_first_nan().

(When we convert the softfloat pickNaNMulAdd routine to also
select a NaN propagation rule at runtime, we will be able to
remove the use_first_nan flag because the propagation rules
will handle everything.)

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Max Filippov <jcmvbkbc@gmail.com>
Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Message-id: 20241025141254.2141506-15-peter.maydell@linaro.org

fpu/softfloat-specialize.c.inc

@@ -405,18 +405,8 @@ static int pickNaN(FloatClass a_cls, FloatClass b_cls,
     || defined(TARGET_TRICORE) || defined(TARGET_ARM) || defined(TARGET_MIPS) \
     || defined(TARGET_LOONGARCH64) || defined(TARGET_HPPA) \
     || defined(TARGET_S390X) || defined(TARGET_PPC) || defined(TARGET_M68K) \
-    || defined(TARGET_SPARC)
+    || defined(TARGET_SPARC) || defined(TARGET_XTENSA)
         g_assert_not_reached();
-#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) {
-            rule = float_2nan_prop_ab;
-        } else {
-            rule = float_2nan_prop_ba;
-        }
 #else
         rule = float_2nan_prop_x87;
 #endif

target/xtensa/fpu_helper.c

@@ -60,6 +60,8 @@ static const struct {
 void xtensa_use_first_nan(CPUXtensaState *env, bool use_first)
 {
     set_use_first_nan(use_first, &env->fp_status);
+    set_float_2nan_prop_rule(use_first ? float_2nan_prop_ab : float_2nan_prop_ba,
+                             &env->fp_status);
 }
 
 void HELPER(wur_fpu2k_fcr)(CPUXtensaState *env, uint32_t v)