From d9e561ab2aacacd26edc19fd45e48e4635be7a2f Mon Sep 17 00:00:00 2001
From: Max Filippov <jcmvbkbc@gmail.com>
Date: Fri, 26 Feb 2021 12:16:49 -0500
Subject: [PATCH] softfloat: add xtensa specialization for pickNaNMulAdd

pickNaNMulAdd logic on Xtensa is to apply pickNaN to the inputs of the
expression (a * b) + c. However if default NaN is produces as a result
of (a * b) calculation it is not considered when c is NaN.
So with two pickNaN variants there must be two pickNaNMulAdd variants.
In addition the invalid flag is always set when (a * b) produces NaN.

Backports commit fbcc38e4cb1b539b8615ec9b0adc285351d77628 from qemu
---
 qemu/fpu/softfloat-specialize.inc.c | 26 ++++++++++++++++++++++++++
 1 file changed, 26 insertions(+)

diff --git a/qemu/fpu/softfloat-specialize.inc.c b/qemu/fpu/softfloat-specialize.inc.c
index 28b6865a..0964a542 100644
--- a/qemu/fpu/softfloat-specialize.inc.c
+++ b/qemu/fpu/softfloat-specialize.inc.c
@@ -578,6 +578,32 @@ static int pickNaNMulAdd(FloatClass a_cls, FloatClass b_cls, FloatClass c_cls,
     } else {
         return 1;
     }
+#elif defined(TARGET_XTENSA)
+    /*
+     * For Xtensa, the (inf,zero,nan) case sets InvalidOp and returns
+     * an input NaN if we have one (ie c).
+     */
+    if (infzero) {
+        float_raise(float_flag_invalid, status);
+        return 2;
+    }
+    if (status->use_first_nan) {
+        if (is_nan(a_cls)) {
+            return 0;
+        } else if (is_nan(b_cls)) {
+            return 1;
+        } else {
+            return 2;
+        }
+    } else {
+        if (is_nan(c_cls)) {
+            return 2;
+        } else if (is_nan(b_cls)) {
+            return 1;
+        } else {
+            return 0;
+        }
+    }
 #else
     /* A default implementation: prefer a to b to c.
      * This is unlikely to actually match any real implementation.