Re: [PATCH 2/4] target/i386: introduce function to set rounding mode from FPCW or MXCSR bits

[Philippe Mathieu-Daudé]

On 19/10/22 17:06, Paolo Bonzini wrote:
> VROUND, FSTCW and STMXCSR all have to perform the same conversion from
> x86 rounding modes to softfloat constants.  Since the ISA is consistent
> on the meaning of the two-bit rounding modes, extract the common code
> into a wrapper for set_float_rounding_mode.
>
> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
> ---
>   target/i386/ops_sse.h        | 60 +++---------------------------------
>   target/i386/tcg/fpu_helper.c | 60 +++++++++++++-----------------------
>   2 files changed, 25 insertions(+), 95 deletions(-)

> diff --git a/target/i386/tcg/fpu_helper.c b/target/i386/tcg/fpu_helper.c
> index a6a90a1817..6f3741b635 100644
> --- a/target/i386/tcg/fpu_helper.c
> +++ b/target/i386/tcg/fpu_helper.c
> @@ -32,7 +32,8 @@
>   #define ST(n)  (env->fpregs[(env->fpstt + (n)) & 7].d)
>   #define ST1    ST(1)
>   
> -#define FPU_RC_MASK         0xc00
> +#define FPU_RC_SHIFT        10
> +#define FPU_RC_MASK         (3 << FPU_RC_SHIFT)
>   #define FPU_RC_NEAR         0x000
>   #define FPU_RC_DOWN         0x400
>   #define FPU_RC_UP           0x800
> @@ -685,28 +686,26 @@ uint32_t helper_fnstcw(CPUX86State *env)
>       return env->fpuc;
>   }
>   
> +static void set_x86_rounding_mode(unsigned mode, float_status *status)
> +{
> +    static FloatRoundMode x86_round_mode[4] = {

static const, otherwise:

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

> +        float_round_nearest_even,
> +        float_round_down,
> +        float_round_up,
> +        float_round_to_zero
> +    };
> +    assert(mode < ARRAY_SIZE(x86_round_mode));
> +    set_float_rounding_mode(x86_round_mode[mode], status);
> +}