Re: [PATCH 12/21] target/sparc: Explicitly set 2-NaN propagation rule

[Mark Cave-Ayland]

On 25/10/2024 15:12, Peter Maydell wrote:

> Set the NaN propagation rule explicitly in the float_status
> words we use.
>
> Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
> ---
>   target/sparc/cpu.c             |  8 ++++++++
>   target/sparc/fop_helper.c      | 10 ++++++++--
>   fpu/softfloat-specialize.c.inc |  6 ++----
>   3 files changed, 18 insertions(+), 6 deletions(-)
>
> diff --git a/target/sparc/cpu.c b/target/sparc/cpu.c
> index e7f4068a162..dd7af86de73 100644
> --- a/target/sparc/cpu.c
> +++ b/target/sparc/cpu.c
> @@ -26,6 +26,7 @@
>   #include "hw/qdev-properties.h"
>   #include "qapi/visitor.h"
>   #include "tcg/tcg.h"
> +#include "fpu/softfloat.h"
>   
>   //#define DEBUG_FEATURES
>   
> @@ -807,6 +808,13 @@ static void sparc_cpu_realizefn(DeviceState *dev, Error **errp)
>       env->version |= env->def.nwindows - 1;
>   #endif
>   
> +    /*
> +     * Prefer SNaN over QNaN, order B then A. It's OK to do this in realize
> +     * rather than reset, because fp_status is after 'end_reset_fields' in
> +     * the CPU state struct so it won't get zeroed on reset.
> +     */
> +    set_float_2nan_prop_rule(float_2nan_prop_s_ba, &env->fp_status);
> +
>       cpu_exec_realizefn(cs, &local_err);
>       if (local_err != NULL) {
>           error_propagate(errp, local_err);
> diff --git a/target/sparc/fop_helper.c b/target/sparc/fop_helper.c
> index b6692382b3b..6f9ccc008a0 100644
> --- a/target/sparc/fop_helper.c
> +++ b/target/sparc/fop_helper.c
> @@ -497,7 +497,10 @@ uint32_t helper_flcmps(float32 src1, float32 src2)
>        * Perform the comparison with a dummy fp environment.
>        */
>       float_status discard = { };
> -    FloatRelation r = float32_compare_quiet(src1, src2, &discard);
> +    FloatRelation r;
> +
> +    set_float_2nan_prop_rule(float_2nan_prop_s_ba, &discard);
> +    r = float32_compare_quiet(src1, src2, &discard);
>   
>       switch (r) {
>       case float_relation_equal:
> @@ -518,7 +521,10 @@ uint32_t helper_flcmps(float32 src1, float32 src2)
>   uint32_t helper_flcmpd(float64 src1, float64 src2)
>   {
>       float_status discard = { };
> -    FloatRelation r = float64_compare_quiet(src1, src2, &discard);
> +    FloatRelation r;
> +
> +    set_float_2nan_prop_rule(float_2nan_prop_s_ba, &discard);
> +    r = float64_compare_quiet(src1, src2, &discard);
>   
>       switch (r) {
>       case float_relation_equal:
> diff --git a/fpu/softfloat-specialize.c.inc b/fpu/softfloat-specialize.c.inc
> index 226632a4d10..8bc95187178 100644
> --- a/fpu/softfloat-specialize.c.inc
> +++ b/fpu/softfloat-specialize.c.inc
> @@ -404,11 +404,9 @@ static int pickNaN(FloatClass a_cls, FloatClass b_cls,
>       || defined(TARGET_RISCV) || defined(TARGET_SH4) \
>       || 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_S390X) || defined(TARGET_PPC) || defined(TARGET_M68K) \
> +    || defined(TARGET_SPARC)
>           g_assert_not_reached();
> -#elif defined(TARGET_SPARC)
> -        /* Prefer SNaN over QNaN, order B then A. */
> -        rule = float_2nan_prop_s_ba;
>   #elif defined(TARGET_XTENSA)
>           /*
>            * Xtensa has two NaN propagation modes.

Acked-by: Mark Cave-Ayland <mark.cave-ayland@ilande.co.uk>


ATB,

Mark.