softfloat: Set 2-NaN propagation rule in float_status, not at compile time

[PATCH 14/21] target/xtensa: Explicitly set 2-NaN propagation rule

Posted by Peter Maydell 4 weeks, 1 day ago

Set the NaN propagation rule explicitly in xtensa_use_first_nan().

(When we convert the softfloat pickNaNMulAdd routine to also
select a NaN propagation rule at runtime, we will be able to
remove the use_first_nan flag because the propagation rules
will handle everything.)

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
---
 target/xtensa/fpu_helper.c     |  2 ++
 fpu/softfloat-specialize.c.inc | 12 +-----------
 2 files changed, 3 insertions(+), 11 deletions(-)

diff --git a/target/xtensa/fpu_helper.c b/target/xtensa/fpu_helper.c
index 50a5efa65e2..f2d212d05df 100644
--- a/target/xtensa/fpu_helper.c
+++ b/target/xtensa/fpu_helper.c
@@ -60,6 +60,8 @@ static const struct {
 void xtensa_use_first_nan(CPUXtensaState *env, bool use_first)
 {
     set_use_first_nan(use_first, &env->fp_status);
+    set_float_2nan_prop_rule(use_first ? float_2nan_prop_ab : float_2nan_prop_ba,
+                             &env->fp_status);
 }
 
 void HELPER(wur_fpu2k_fcr)(CPUXtensaState *env, uint32_t v)
diff --git a/fpu/softfloat-specialize.c.inc b/fpu/softfloat-specialize.c.inc
index 8bc95187178..b050c5eb04a 100644
--- a/fpu/softfloat-specialize.c.inc
+++ b/fpu/softfloat-specialize.c.inc
@@ -405,18 +405,8 @@ static int pickNaN(FloatClass a_cls, FloatClass b_cls,
     || defined(TARGET_TRICORE) || defined(TARGET_ARM) || defined(TARGET_MIPS) \
     || defined(TARGET_LOONGARCH64) || defined(TARGET_HPPA) \
     || defined(TARGET_S390X) || defined(TARGET_PPC) || defined(TARGET_M68K) \
-    || defined(TARGET_SPARC)
+    || defined(TARGET_SPARC) || defined(TARGET_XTENSA)
         g_assert_not_reached();
-#elif defined(TARGET_XTENSA)
-        /*
-         * Xtensa has two NaN propagation modes.
-         * Which one is active is controlled by float_status::use_first_nan.
-         */
-        if (status->use_first_nan) {
-            rule = float_2nan_prop_ab;
-        } else {
-            rule = float_2nan_prop_ba;
-        }
 #else
         rule = float_2nan_prop_x87;
 #endif
-- 
2.34.1

Re: [PATCH 14/21] target/xtensa: Explicitly set 2-NaN propagation rule

Posted by Richard Henderson 3 weeks, 5 days ago

On 10/25/24 15:12, Peter Maydell wrote:
> Set the NaN propagation rule explicitly in xtensa_use_first_nan().
> 
> (When we convert the softfloat pickNaNMulAdd routine to also
> select a NaN propagation rule at runtime, we will be able to
> remove the use_first_nan flag because the propagation rules
> will handle everything.)
> 
> Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
> ---
>   target/xtensa/fpu_helper.c     |  2 ++
>   fpu/softfloat-specialize.c.inc | 12 +-----------
>   2 files changed, 3 insertions(+), 11 deletions(-)

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


r~

Re: [PATCH 14/21] target/xtensa: Explicitly set 2-NaN propagation rule

Posted by Philippe Mathieu-Daudé 4 weeks ago

On 25/10/24 11:12, Peter Maydell wrote:
> Set the NaN propagation rule explicitly in xtensa_use_first_nan().
> 
> (When we convert the softfloat pickNaNMulAdd routine to also
> select a NaN propagation rule at runtime, we will be able to
> remove the use_first_nan flag because the propagation rules
> will handle everything.)
> 
> Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
> ---
>   target/xtensa/fpu_helper.c     |  2 ++
>   fpu/softfloat-specialize.c.inc | 12 +-----------
>   2 files changed, 3 insertions(+), 11 deletions(-)

Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>

Re: [PATCH 14/21] target/xtensa: Explicitly set 2-NaN propagation rule

Posted by Max Filippov 4 weeks, 1 day ago

On Fri, Oct 25, 2024 at 7:13 AM Peter Maydell <peter.maydell@linaro.org> wrote:
>
> Set the NaN propagation rule explicitly in xtensa_use_first_nan().
>
> (When we convert the softfloat pickNaNMulAdd routine to also
> select a NaN propagation rule at runtime, we will be able to
> remove the use_first_nan flag because the propagation rules
> will handle everything.)
>
> Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
> ---
>  target/xtensa/fpu_helper.c     |  2 ++
>  fpu/softfloat-specialize.c.inc | 12 +-----------
>  2 files changed, 3 insertions(+), 11 deletions(-)

Reviewed-by: Max Filippov <jcmvbkbc@gmail.com>

-- 
Thanks.
-- Max