Commit 0bcfbcbe authored by Richard Henderson's avatar Richard Henderson
Browse files

fpu/softfloat: Replace float_class_msnan with parts_silence_nan 



With a canonical representation of NaNs, we can silence an SNaN
immediately rather than delay until the final format is known.

Tested-by: default avatarAlex Bennée <alex.bennee@linaro.org>
Reviewed-by: default avatarAlex Bennée <alex.bennee@linaro.org>
Reviewed-by: default avatarPeter Maydell <peter.maydell@linaro.org>
Signed-off-by: default avatarRichard Henderson <richard.henderson@linaro.org>
parent f7e598e2

fpu/softfloat-specialize.h

+23 −0
Original line number Diff line number Diff line
@@ -138,6 +138,29 @@ static FloatParts parts_default_nan(float_status *status) 
    };

}



/*----------------------------------------------------------------------------

| Returns a quiet NaN from a signalling NaN for the deconstructed

| floating-point parts.

*----------------------------------------------------------------------------*/



static FloatParts parts_silence_nan(FloatParts a, float_status *status)

{

#ifdef NO_SIGNALING_NANS

    g_assert_not_reached();

#elif defined(TARGET_HPPA)

    a.frac &= ~(1ULL << (DECOMPOSED_BINARY_POINT - 1));

    a.frac |= 1ULL << (DECOMPOSED_BINARY_POINT - 2);

#else

    if (status->snan_bit_is_one) {

        return parts_default_nan(status);

    } else {

        a.frac |= 1ULL << (DECOMPOSED_BINARY_POINT - 1);

    }

#endif

    a.cls = float_class_qnan;

    return a;

}



/*----------------------------------------------------------------------------

| The pattern for a default generated half-precision NaN.

*----------------------------------------------------------------------------*/

fpu/softfloat.c

+10 −30
Original line number Diff line number Diff line
@@ -188,7 +188,6 @@ typedef enum __attribute__ ((__packed__)) { 
    float_class_inf,

    float_class_qnan,  /* all NaNs from here */

    float_class_snan,

    float_class_msnan, /* maybe silenced */

} FloatClass;



/*
@@ -492,14 +491,7 @@ static FloatParts float16_unpack_canonical(float16 f, float_status *s) 


static float16 float16_round_pack_canonical(FloatParts p, float_status *s)

{

    switch (p.cls) {

    case float_class_msnan:

        p.frac >>= float16_params.frac_shift;

        return float16_maybe_silence_nan(float16_pack_raw(p), s);

    default:

        p = round_canonical(p, s, &float16_params);

        return float16_pack_raw(p);

    }

    return float16_pack_raw(round_canonical(p, s, &float16_params));

}



static FloatParts float32_unpack_canonical(float32 f, float_status *s)
@@ -509,14 +501,7 @@ static FloatParts float32_unpack_canonical(float32 f, float_status *s) 


static float32 float32_round_pack_canonical(FloatParts p, float_status *s)

{

    switch (p.cls) {

    case float_class_msnan:

        p.frac >>= float32_params.frac_shift;

        return float32_maybe_silence_nan(float32_pack_raw(p), s);

    default:

        p = round_canonical(p, s, &float32_params);

        return float32_pack_raw(p);

    }

    return float32_pack_raw(round_canonical(p, s, &float32_params));

}



static FloatParts float64_unpack_canonical(float64 f, float_status *s)
@@ -526,14 +511,7 @@ static FloatParts float64_unpack_canonical(float64 f, float_status *s) 


static float64 float64_round_pack_canonical(FloatParts p, float_status *s)

{

    switch (p.cls) {

    case float_class_msnan:

        p.frac >>= float64_params.frac_shift;

        return float64_maybe_silence_nan(float64_pack_raw(p), s);

    default:

        p = round_canonical(p, s, &float64_params);

        return float64_pack_raw(p);

    }

    return float64_pack_raw(round_canonical(p, s, &float64_params));

}



/* Simple helpers for checking if what NaN we have */
@@ -555,7 +533,7 @@ static FloatParts return_nan(FloatParts a, float_status *s) 
    switch (a.cls) {

    case float_class_snan:

        s->float_exception_flags |= float_flag_invalid;

        a.cls = float_class_msnan;

        a = parts_silence_nan(a, s);

        /* fall through */

    case float_class_qnan:

        if (s->default_nan_mode) {
@@ -584,7 +562,9 @@ static FloatParts pick_nan(FloatParts a, FloatParts b, float_status *s) 
                    (a.frac == b.frac && a.sign < b.sign))) {

            a = b;

        }

        a.cls = float_class_msnan;

        if (is_snan(a.cls)) {

            return parts_silence_nan(a, s);

        }

    }

    return a;

}
@@ -624,8 +604,10 @@ static FloatParts pick_nan_muladd(FloatParts a, FloatParts b, FloatParts c, 
    default:

        g_assert_not_reached();

    }

    a.cls = float_class_msnan;



    if (is_snan(a.cls)) {

        return parts_silence_nan(a, s);

    }

    return a;

}
@@ -1334,7 +1316,6 @@ static int64_t round_to_int_and_pack(FloatParts in, int rmode, 
    switch (p.cls) {

    case float_class_snan:

    case float_class_qnan:

    case float_class_msnan:

        s->float_exception_flags = orig_flags | float_flag_invalid;

        return max;

    case float_class_inf:
@@ -1425,7 +1406,6 @@ static uint64_t round_to_uint_and_pack(FloatParts in, int rmode, uint64_t max, 
    switch (p.cls) {

    case float_class_snan:

    case float_class_qnan:

    case float_class_msnan:

        s->float_exception_flags = orig_flags | float_flag_invalid;

        return max;

    case float_class_inf: