target/arm: Set Float3NaNPropRule explicitly

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

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Message-id: 20241202131347.498124-18-peter.maydell@linaro.org

1 files changed, 5 insertions, 0 deletions

diff --git a/target/arm/cpu.c b/target/arm/cpu.c
index ead3979398..c81f6df3fc 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);
 }