Richard Henderson <richard.hender...@linaro.org> writes:
> Signed-off-by: Richard Henderson <richard.hender...@linaro.org>
> ---
> include/fpu/softfloat.h | 2 +
> fpu/softfloat.c | 416 +++++++++++++++++++++++++++++++++++++++-
> tests/fp/fp-test.c | 2 +-
> tests/fp/wrap.c.inc | 12 ++
> 4 files changed, 430 insertions(+), 2 deletions(-)
>
> diff --git a/include/fpu/softfloat.h b/include/fpu/softfloat.h
> index 78ad5ca738..a38433deb4 100644
> --- a/include/fpu/softfloat.h
> +++ b/include/fpu/softfloat.h
> @@ -1196,6 +1196,8 @@ float128 float128_sub(float128, float128, float_status
> *status);
> float128 float128_mul(float128, float128, float_status *status);
> float128 float128_div(float128, float128, float_status *status);
> float128 float128_rem(float128, float128, float_status *status);
> +float128 float128_muladd(float128, float128, float128, int,
> + float_status *status);
> float128 float128_sqrt(float128, float_status *status);
> FloatRelation float128_compare(float128, float128, float_status *status);
> FloatRelation float128_compare_quiet(float128, float128, float_status
> *status);
> diff --git a/fpu/softfloat.c b/fpu/softfloat.c
> index e038434a07..49de31fec2 100644
> --- a/fpu/softfloat.c
> +++ b/fpu/softfloat.c
> @@ -512,11 +512,19 @@ static inline __attribute__((unused)) bool
> is_qnan(FloatClass c)
>
> typedef struct {
> uint64_t frac;
> - int32_t exp;
> + int32_t exp;
> FloatClass cls;
> bool sign;
> } FloatParts;
>
> +/* Similar for float128. */
> +typedef struct {
> + uint64_t frac0, frac1;
> + int32_t exp;
> + FloatClass cls;
> + bool sign;
> +} FloatParts128;
> +
> #define DECOMPOSED_BINARY_POINT (64 - 2)
> #define DECOMPOSED_IMPLICIT_BIT (1ull << DECOMPOSED_BINARY_POINT)
> #define DECOMPOSED_OVERFLOW_BIT (DECOMPOSED_IMPLICIT_BIT << 1)
> @@ -4574,6 +4582,46 @@ static void
>
> }
>
> +/*----------------------------------------------------------------------------
> +| Returns the parts of floating-point value `a'.
> +*----------------------------------------------------------------------------*/
> +
> +static void float128_unpack(FloatParts128 *p, float128 a, float_status
> *status)
> +{
> + p->sign = extractFloat128Sign(a);
> + p->exp = extractFloat128Exp(a);
> + p->frac0 = extractFloat128Frac0(a);
> + p->frac1 = extractFloat128Frac1(a);
Here we are deviating from the exiting style, it would be nice if we
could separate the raw unpack and have something like:
static const FloatFmt float128_params = {
FLOAT_PARAMS(15, 112)
}
static inline FloatParts128 unpack128_raw(FloatFmt fmt, uint128_t raw)
{
const int sign_pos = fmt.frac_size + fmt.exp_size;
return (FloatParts128) {
.cls = float_class_unclassified,
.sign = extract128(raw, sign_pos, 1),
.exp = extract128(raw, fmt.frac_size, fmt.exp_size),
.frac1 = extract128_lo(raw, 0, fmt.frac_size),
.frac2 = extract128_hi(raw, 0, fmt.frac_size),
};
}
So even if we end up duplicating a chunk of the code the form will be
similar so when we side-by-side the logic we can see it works the same
way.
> +
> + if (p->exp == 0) {
> + if ((p->frac0 | p->frac1) == 0) {
> + p->cls = float_class_zero;
> + } else if (status->flush_inputs_to_zero) {
> + float_raise(float_flag_input_denormal, status);
> + p->cls = float_class_zero;
> + p->frac0 = p->frac1 = 0;
> + } else {
> + normalizeFloat128Subnormal(p->frac0, p->frac1, &p->exp,
> + &p->frac0, &p->frac1);
> + p->exp -= 0x3fff;
> + p->cls = float_class_normal;
> + }
and also we can get avoid introducing the magic numbers into the code.
> + } else if (p->exp == 0x7fff) {
> + if ((p->frac0 | p->frac1) == 0) {
> + p->cls = float_class_inf;
> + } else if (float128_is_signaling_nan(a, status)) {
> + p->cls = float_class_snan;
> + } else {
> + p->cls = float_class_qnan;
> + }
> + } else {
> + /* Add the implicit bit. */
> + p->frac0 |= UINT64_C(0x0001000000000000);
> + p->exp -= 0x3fff;
> + p->cls = float_class_normal;
> + }
> +}
> +
and eventually hold out for compilers smart enough to handle unification
at a later date.
>
> /*----------------------------------------------------------------------------
> | Packs the sign `zSign', the exponent `zExp', and the significand formed
> | by the concatenation of `zSig0' and `zSig1' into a quadruple-precision
> @@ -7205,6 +7253,372 @@ float128 float128_mul(float128 a, float128 b,
> float_status *status)
>
> }
>
> +typedef struct UInt256 {
> + /* Indexed big-endian, to match the rest of softfloat numbering. */
> + uint64_t w[4];
> +} UInt256;
> +
> +static inline uint64_t shl_double(uint64_t h, uint64_t l, unsigned lsh)
> +{
> + return lsh ? (h << lsh) | (l >> (64 - lsh)) : h;
> +}
> +
> +static inline uint64_t shr_double(uint64_t h, uint64_t l, unsigned rsh)
> +{
> + return rsh ? (h << (64 - rsh)) | (l >> rsh) : l;
> +}
> +
> +static void shortShift256Left(UInt256 *p, unsigned lsh)
> +{
> + if (lsh != 0) {
> + p->w[0] = shl_double(p->w[0], p->w[1], lsh);
> + p->w[1] = shl_double(p->w[1], p->w[2], lsh);
> + p->w[2] = shl_double(p->w[2], p->w[3], lsh);
> + p->w[3] <<= lsh;
> + }
> +}
> +
> +static inline void shift256RightJamming(UInt256 *p, unsigned count)
> +{
> + uint64_t out, p0, p1, p2, p3;
> +
> + p0 = p->w[0];
> + p1 = p->w[1];
> + p2 = p->w[2];
> + p3 = p->w[3];
> +
> + if (unlikely(count == 0)) {
> + return;
> + } else if (likely(count < 64)) {
> + out = 0;
> + } else if (likely(count < 256)) {
> + if (count < 128) {
> + out = p3;
> + p3 = p2;
> + p2 = p1;
> + p1 = p0;
> + p0 = 0;
> + } else if (count < 192) {
> + out = p2 | p3;
> + p3 = p1;
> + p2 = p0;
> + p1 = 0;
> + p0 = 0;
> + } else {
> + out = p1 | p2 | p3;
> + p3 = p0;
> + p2 = 0;
> + p1 = 0;
> + p0 = 0;
> + }
> + count &= 63;
> + if (count == 0) {
> + goto done;
> + }
> + } else {
> + out = p0 | p1 | p2 | p3;
> + p3 = 0;
> + p2 = 0;
> + p1 = 0;
> + p0 = 0;
> + goto done;
> + }
> +
> + out |= shr_double(p3, 0, count);
> + p3 = shr_double(p2, p3, count);
> + p2 = shr_double(p1, p2, count);
> + p1 = shr_double(p0, p1, count);
> + p0 = p0 >> count;
> +
> + done:
> + p->w[3] = p3 | (out != 0);
> + p->w[2] = p2;
> + p->w[1] = p1;
> + p->w[0] = p0;
> +}
> +
> +/* R = A - B */
> +static void sub256(UInt256 *r, UInt256 *a, UInt256 *b)
> +{
> + bool borrow = false;
> +
> + for (int i = 3; i >= 0; --i) {
> + uint64_t at = a->w[i];
> + uint64_t bt = b->w[i];
> + uint64_t rt = at - bt;
> +
> + if (borrow) {
> + borrow = at <= bt;
> + rt -= 1;
> + } else {
> + borrow = at < bt;
> + }
> + r->w[i] = rt;
> + }
> +}
> +
> +/* A = -A */
> +static void neg256(UInt256 *a)
> +{
> + /*
> + * Recall that -X - 1 = ~X, and that since this is negation,
> + * once we find a non-zero number, all subsequent words will
> + * have borrow-in, and thus use NOT.
> + */
> + uint64_t t = a->w[3];
> + if (likely(t)) {
> + a->w[3] = -t;
> + goto not2;
> + }
> + t = a->w[2];
> + if (likely(t)) {
> + a->w[2] = -t;
> + goto not1;
> + }
> + t = a->w[1];
> + if (likely(t)) {
> + a->w[1] = -t;
> + goto not0;
> + }
> + a->w[0] = -a->w[0];
> + return;
> + not2:
> + a->w[2] = ~a->w[2];
> + not1:
> + a->w[1] = ~a->w[1];
> + not0:
> + a->w[0] = ~a->w[0];
> +}
> +
> +/* A += B */
> +static void add256(UInt256 *a, UInt256 *b)
> +{
> + bool carry = false;
> +
> + for (int i = 3; i >= 0; --i) {
> + uint64_t bt = b->w[i];
> + uint64_t at = a->w[i] + bt;
> +
> + if (carry) {
> + at += 1;
> + carry = at <= bt;
> + } else {
> + carry = at < bt;
> + }
> + a->w[i] = at;
> + }
> +}
> +
> +float128 float128_muladd(float128 a_f, float128 b_f, float128 c_f,
> + int flags, float_status *status)
> +{
> + bool inf_zero, p_sign, sign_flip;
> + int p_exp, exp_diff, shift, ab_mask, abc_mask;
> + FloatParts128 a, b, c;
> + FloatClass p_cls;
> + UInt256 p_frac, c_frac;
> +
> + float128_unpack(&a, a_f, status);
> + float128_unpack(&b, b_f, status);
> + float128_unpack(&c, c_f, status);
> +
> + ab_mask = float_cmask(a.cls) | float_cmask(b.cls);
> + abc_mask = float_cmask(c.cls) | ab_mask;
> + inf_zero = ab_mask == float_cmask_infzero;
> +
> + /* If any input is a NaN, select the required result. */
> + if (unlikely(abc_mask & float_cmask_anynan)) {
> + if (unlikely(abc_mask & float_cmask_snan)) {
> + float_raise(float_flag_invalid, status);
> + }
> +
> + int which = pickNaNMulAdd(a.cls, b.cls, c.cls, inf_zero, status);
> + if (status->default_nan_mode) {
> + which = 3;
> + }
> + switch (which) {
> + case 0:
> + break;
> + case 1:
> + a_f = b_f;
> + a.cls = b.cls;
> + break;
> + case 2:
> + a_f = c_f;
> + a.cls = c.cls;
> + break;
> + case 3:
> + return float128_default_nan(status);
> + }
> + if (is_snan(a.cls)) {
> + return float128_silence_nan(a_f, status);
> + }
> + return a_f;
> + }
> +
> + /* After dealing with input NaNs, look for Inf * Zero. */
> + if (unlikely(inf_zero)) {
> + float_raise(float_flag_invalid, status);
> + return float128_default_nan(status);
> + }
> +
> + p_sign = a.sign ^ b.sign;
> +
> + if (flags & float_muladd_negate_c) {
> + c.sign ^= 1;
> + }
> + if (flags & float_muladd_negate_product) {
> + p_sign ^= 1;
> + }
> + sign_flip = (flags & float_muladd_negate_result);
> +
> + if (ab_mask & float_cmask_inf) {
> + p_cls = float_class_inf;
> + } else if (ab_mask & float_cmask_zero) {
> + p_cls = float_class_zero;
> + } else {
> + p_cls = float_class_normal;
> + }
> +
> + if (c.cls == float_class_inf) {
> + if (p_cls == float_class_inf && p_sign != c.sign) {
> + /* +Inf + -Inf = NaN */
> + float_raise(float_flag_invalid, status);
> + return float128_default_nan(status);
> + }
> + /* Inf + Inf = Inf of the proper sign; reuse the return below. */
> + p_cls = float_class_inf;
> + p_sign = c.sign;
> + }
> +
> + if (p_cls == float_class_inf) {
> + return packFloat128(p_sign ^ sign_flip, 0x7fff, 0, 0);
> + }
> +
> + if (p_cls == float_class_zero) {
> + if (c.cls == float_class_zero) {
> + if (p_sign != c.sign) {
> + p_sign = status->float_rounding_mode == float_round_down;
> + }
> + return packFloat128(p_sign ^ sign_flip, 0, 0, 0);
> + }
> +
> + if (flags & float_muladd_halve_result) {
> + c.exp -= 1;
> + }
> + return roundAndPackFloat128(c.sign ^ sign_flip,
> + c.exp + 0x3fff - 1,
> + c.frac0, c.frac1, 0, status);
> + }
> +
> + /* a & b should be normals now... */
> + assert(a.cls == float_class_normal && b.cls == float_class_normal);
> +
> + /* Multiply of 2 113-bit numbers produces a 226-bit result. */
> + mul128To256(a.frac0, a.frac1, b.frac0, b.frac1,
> + &p_frac.w[0], &p_frac.w[1], &p_frac.w[2], &p_frac.w[3]);
> +
> + /* Realign the binary point at bit 48 of p_frac[0]. */
> + shift = clz64(p_frac.w[0]) - 15;
> + shortShift256Left(&p_frac, shift);
> + p_exp = a.exp + b.exp - (shift - 16);
> + exp_diff = p_exp - c.exp;
> +
> + /* Extend the fraction part of the addend to 256 bits. */
> + c_frac.w[0] = c.frac0;
> + c_frac.w[1] = c.frac1;
> + c_frac.w[2] = 0;
> + c_frac.w[3] = 0;
> +
> + /* Add or subtract C from the intermediate product. */
> + if (c.cls == float_class_zero) {
> + /* Fall through to rounding after addition (with zero). */
> + } else if (p_sign != c.sign) {
> + /* Subtraction */
> + if (exp_diff < 0) {
> + shift256RightJamming(&p_frac, -exp_diff);
> + sub256(&p_frac, &c_frac, &p_frac);
> + p_exp = c.exp;
> + p_sign ^= 1;
> + } else if (exp_diff > 0) {
> + shift256RightJamming(&c_frac, exp_diff);
> + sub256(&p_frac, &p_frac, &c_frac);
> + } else {
> + /* Low 128 bits of C are known to be zero. */
> + sub128(p_frac.w[0], p_frac.w[1], c_frac.w[0], c_frac.w[1],
> + &p_frac.w[0], &p_frac.w[1]);
> + /*
> + * Since we have normalized to bit 48 of p_frac[0],
> + * a negative result means C > P and we need to invert.
> + */
> + if ((int64_t)p_frac.w[0] < 0) {
> + neg256(&p_frac);
> + p_sign ^= 1;
> + }
> + }
> +
> + /*
> + * Gross normalization of the 256-bit subtraction result.
> + * Fine tuning below shared with addition.
> + */
> + if (p_frac.w[0] != 0) {
> + /* nothing to do */
> + } else if (p_frac.w[1] != 0) {
> + p_exp -= 64;
> + p_frac.w[0] = p_frac.w[1];
> + p_frac.w[1] = p_frac.w[2];
> + p_frac.w[2] = p_frac.w[3];
> + p_frac.w[3] = 0;
> + } else if (p_frac.w[2] != 0) {
> + p_exp -= 128;
> + p_frac.w[0] = p_frac.w[2];
> + p_frac.w[1] = p_frac.w[3];
> + p_frac.w[2] = 0;
> + p_frac.w[3] = 0;
> + } else if (p_frac.w[3] != 0) {
> + p_exp -= 192;
> + p_frac.w[0] = p_frac.w[3];
> + p_frac.w[1] = 0;
> + p_frac.w[2] = 0;
> + p_frac.w[3] = 0;
> + } else {
> + /* Subtraction was exact: result is zero. */
> + p_sign = status->float_rounding_mode == float_round_down;
> + return packFloat128(p_sign ^ sign_flip, 0, 0, 0);
> + }
> + } else {
> + /* Addition */
> + if (exp_diff <= 0) {
> + shift256RightJamming(&p_frac, -exp_diff);
> + /* Low 128 bits of C are known to be zero. */
> + add128(p_frac.w[0], p_frac.w[1], c_frac.w[0], c_frac.w[1],
> + &p_frac.w[0], &p_frac.w[1]);
> + p_exp = c.exp;
> + } else {
> + shift256RightJamming(&c_frac, exp_diff);
> + add256(&p_frac, &c_frac);
> + }
> + }
> +
> + /* Fine normalization of the 256-bit result: p_frac[0] != 0. */
> + shift = clz64(p_frac.w[0]) - 15;
> + if (shift < 0) {
> + shift256RightJamming(&p_frac, -shift);
> + } else if (shift > 0) {
> + shortShift256Left(&p_frac, shift);
> + }
> + p_exp -= shift;
> +
> + if (flags & float_muladd_halve_result) {
> + p_exp -= 1;
> + }
> + return roundAndPackFloat128(p_sign ^ sign_flip,
> + p_exp + 0x3fff - 1,
> + p_frac.w[0], p_frac.w[1],
> + p_frac.w[2] | (p_frac.w[3] != 0),
> + status);
> +}
> +
>
> /*----------------------------------------------------------------------------
> | Returns the result of dividing the quadruple-precision floating-point value
> | `a' by the corresponding value `b'. The operation is performed according
> to
> diff --git a/tests/fp/fp-test.c b/tests/fp/fp-test.c
> index 06ffebd6db..9bbb0dba67 100644
> --- a/tests/fp/fp-test.c
> +++ b/tests/fp/fp-test.c
> @@ -717,7 +717,7 @@ static void do_testfloat(int op, int rmode, bool exact)
> test_abz_f128(true_abz_f128M, subj_abz_f128M);
> break;
> case F128_MULADD:
> - not_implemented();
> + test_abcz_f128(slow_f128M_mulAdd, qemu_f128_mulAdd);
> break;
> case F128_SQRT:
> test_az_f128(slow_f128M_sqrt, qemu_f128M_sqrt);
> diff --git a/tests/fp/wrap.c.inc b/tests/fp/wrap.c.inc
> index 0cbd20013e..65a713deae 100644
> --- a/tests/fp/wrap.c.inc
> +++ b/tests/fp/wrap.c.inc
> @@ -574,6 +574,18 @@ WRAP_MULADD(qemu_f32_mulAdd, float32_muladd, float32)
> WRAP_MULADD(qemu_f64_mulAdd, float64_muladd, float64)
> #undef WRAP_MULADD
>
> +static void qemu_f128_mulAdd(const float128_t *ap, const float128_t *bp,
> + const float128_t *cp, float128_t *res)
> +{
> + float128 a, b, c, ret;
> +
> + a = soft_to_qemu128(*ap);
> + b = soft_to_qemu128(*bp);
> + c = soft_to_qemu128(*cp);
> + ret = float128_muladd(a, b, c, 0, &qsf);
> + *res = qemu_to_soft128(ret);
> +}
> +
> #define WRAP_CMP16(name, func, retcond) \
> static bool name(float16_t a, float16_t b) \
> { \
--
Alex Bennée
