Set the Float3NaNPropRule explicitly for Arm, and remove the
ifdef from pickNaNMulAdd().

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
---
 target/arm/cpu.c               | 5 +++++
 fpu/softfloat-specialize.c.inc | 8 +-------
 2 files changed, 6 insertions(+), 7 deletions(-)

diff --git a/target/arm/cpu.c b/target/arm/cpu.c
index ead39793985..c81f6df3fca 100644
--- a/target/arm/cpu.c
+++ b/target/arm/cpu.c
@@ -173,6 +173,10 @@ void arm_register_el_change_hook(ARMCPU *cpu, ARMELChangeHookFn *hook,
  *  * tininess-before-rounding
  *  * 2-input NaN propagation prefers SNaN over QNaN, and then
  *    operand A over operand B (see FPProcessNaNs() pseudocode)
+ *  * 3-input NaN propagation prefers SNaN over QNaN, and then
+ *    operand C over A over B (see FPProcessNaNs3() pseudocode,
+ *    but note that for QEMU muladd is a * b + c, whereas for
+ *    the pseudocode function the arguments are in the order c, a, b.
  *  * 0 * Inf + NaN returns the default NaN if the input NaN is quiet,
  *    and the input NaN if it is signalling
  */
@@ -180,6 +184,7 @@ static void arm_set_default_fp_behaviours(float_status *s)
 {
     set_float_detect_tininess(float_tininess_before_rounding, s);
     set_float_2nan_prop_rule(float_2nan_prop_s_ab, s);
+    set_float_3nan_prop_rule(float_3nan_prop_s_cab, s);
     set_float_infzeronan_rule(float_infzeronan_dnan_if_qnan, s);
 }
 
diff --git a/fpu/softfloat-specialize.c.inc b/fpu/softfloat-specialize.c.inc
index d7c0c90ea65..9b5243c9529 100644
--- a/fpu/softfloat-specialize.c.inc
+++ b/fpu/softfloat-specialize.c.inc
@@ -502,13 +502,7 @@ static int pickNaNMulAdd(FloatClass a_cls, FloatClass b_cls, FloatClass c_cls,
     }
 
     if (rule == float_3nan_prop_none) {
-#if defined(TARGET_ARM)
-        /*
-         * This looks different from the ARM ARM pseudocode, because the ARM ARM
-         * puts the operands to a fused mac operation (a*b)+c in the order c,a,b
-         */
-        rule = float_3nan_prop_s_cab;
-#elif defined(TARGET_MIPS)
+#if defined(TARGET_MIPS)
         if (snan_bit_is_one(status)) {
             rule = float_3nan_prop_s_abc;
         } else {
-- 
2.34.1

On 11/28/24 04:43, Peter Maydell wrote:
> Set the Float3NaNPropRule explicitly for Arm, and remove the
> ifdef from pickNaNMulAdd().
> 
> Signed-off-by: Peter Maydell<peter.maydell@linaro.org>
> ---
>   target/arm/cpu.c               | 5 +++++
>   fpu/softfloat-specialize.c.inc | 8 +-------
>   2 files changed, 6 insertions(+), 7 deletions(-)

Reviewed-by: Richard Henderson <richard.henderson@linaro.org>

r~