[Qemu-devel] [PATCH 2/2] ARM: Implement correct NaN propagation rules

[Peter Maydell <peter.maydell@linaro.org>]

Implement the correct NaN propagation rules for ARM targets by
providing an appropriate pickNaN function.

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
---
 fpu/softfloat-specialize.h |   23 +++++++++++++++++++++++
 1 files changed, 23 insertions(+), 0 deletions(-)

diff --git a/fpu/softfloat-specialize.h b/fpu/softfloat-specialize.h
index 3015480..fd1b114 100644
--- a/fpu/softfloat-specialize.h
+++ b/fpu/softfloat-specialize.h
@@ -149,6 +149,28 @@ static float32 commonNaNToFloat32( commonNaNT a )
 | tie-break rule.
 *----------------------------------------------------------------------------*/
 
+#if defined(TARGET_ARM)
+static int pickNaN(flag aIsQNaN, flag aIsSNaN, flag bIsQNaN, flag bIsSNaN,
+                    flag aIsLargerSignificand)
+{
+    /* ARM mandated NaN propagation rules: take the first of:
+     *  1. A if it is signaling
+     *  2. B if it is signaling
+     *  3. A (quiet)
+     *  4. B (quiet)
+     * A signaling NaN is always quietened before returning it.
+     */
+    if (aIsSNaN) {
+        return 0;
+    } else if (bIsSNaN) {
+        return 1;
+    } else if (aIsQNaN) {
+        return 0;
+    } else {
+        return 1;
+    }
+}
+#else
 static int pickNaN(flag aIsQNaN, flag aIsSNaN, flag bIsQNaN, flag bIsSNaN,
                     flag aIsLargerSignificand)
 {
@@ -178,6 +200,7 @@ static int pickNaN(flag aIsQNaN, flag aIsSNaN, flag bIsQNaN, flag bIsSNaN,
         return 1;
     }
 }
+#endif
 
 /*----------------------------------------------------------------------------
 | Takes two single-precision floating-point values `a' and `b', one of which
-- 
1.6.3.3