[Qemu-devel] [PATCH v3] target/mips: Fix minor bug in FPU

[Mateja Marjanovic]

From: Mateja Marjanovic <address@hidden>

Wrong type of NaN was generated for IEEE 754-2008 by MADDF.<D|S> and
MSUBF.<D|S> instructions when the arguments were (inf, zero, nan) or
(zero, inf, nan).
These instructions were tested and the results match with the results
of the machine that has a MIPS64 r6 cpu.

Signed-off-by: Mateja Marjanovic <address@hidden>
---
 fpu/softfloat-specialize.h | 24 ++++++++++++++++--------
 1 file changed, 16 insertions(+), 8 deletions(-)

diff --git a/fpu/softfloat-specialize.h b/fpu/softfloat-specialize.h
index 16c0bcb..7b88957 100644
--- a/fpu/softfloat-specialize.h
+++ b/fpu/softfloat-specialize.h
@@ -495,15 +495,15 @@ static int pickNaNMulAdd(FloatClass a_cls, FloatClass 
b_cls, FloatClass c_cls,
         return 1;
     }
 #elif defined(TARGET_MIPS)
-    /* For MIPS, the (inf,zero,qnan) case sets InvalidOp and returns
-     * the default NaN
-     */
-    if (infzero) {
-        float_raise(float_flag_invalid, status);
-        return 3;
-    }
-
     if (snan_bit_is_one(status)) {
+        /*
+         * For MIPS systems that conform to IEEE754-1985, the (inf,zero,nan)
+         * case sets InvalidOp and returns the default NaN
+         */
+        if (infzero) {
+            float_raise(float_flag_invalid, status);
+            return 3;
+        }
         /* Prefer sNaN over qNaN, in the a, b, c order. */
         if (is_snan(a_cls)) {
             return 0;
@@ -519,6 +519,14 @@ static int pickNaNMulAdd(FloatClass a_cls, FloatClass 
b_cls, FloatClass c_cls,
             return 2;
         }
     } else {
+        /*
+         * For MIPS systems that conform to IEEE754-2008, the (inf,zero,nan)
+         * case sets InvalidOp and returns the input value 'c'
+         */
+        if (infzero) {
+            float_raise(float_flag_invalid, status);
+            return 2;
+        }
         /* Prefer sNaN over qNaN, in the c, a, b order. */
         if (is_snan(c_cls)) {
             return 2;
-- 
2.7.4