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softfloat: Convert float128_silence_nan to parts
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This is the minimal change that also introduces float128_params,
float128_unpack_raw, and float128_pack_raw without running into
unused symbol Werrors.

Reviewed-by: Alex Bennée <alex.bennee@linaro.org>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
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@rth7680
rth7680 committed May 16, 2021
1 parent 4109b9e commit 0018b1f
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Showing 2 changed files with 89 additions and 32 deletions.
25 changes: 6 additions & 19 deletions fpu/softfloat-specialize.c.inc
View file
Expand Up @@ -197,6 +197,12 @@ static void parts64_silence_nan(FloatParts64 *p, float_status *status)
p->cls = float_class_qnan;
}

static void parts128_silence_nan(FloatParts128 *p, float_status *status)
{
p->frac_hi = parts_silence_nan_frac(p->frac_hi, status);
p->cls = float_class_qnan;
}

/*----------------------------------------------------------------------------
| The pattern for a default generated extended double-precision NaN.
*----------------------------------------------------------------------------*/
Expand Down Expand Up @@ -1062,25 +1068,6 @@ bool float128_is_signaling_nan(float128 a, float_status *status)
}
}

/*----------------------------------------------------------------------------
| Returns a quiet NaN from a signalling NaN for the quadruple-precision
| floating point value `a'.
*----------------------------------------------------------------------------*/

float128 float128_silence_nan(float128 a, float_status *status)
{
if (no_signaling_nans(status)) {
g_assert_not_reached();
} else {
if (snan_bit_is_one(status)) {
return float128_default_nan(status);
} else {
a.high |= UINT64_C(0x0000800000000000);
return a;
}
}
}

/*----------------------------------------------------------------------------
| Returns the result of converting the quadruple-precision floating-point NaN
| `a' to the canonical NaN format. If `a' is a signaling NaN, the invalid
Expand Down
96 changes: 83 additions & 13 deletions fpu/softfloat.c
View file
Expand Up @@ -500,14 +500,12 @@ static inline __attribute__((unused)) bool is_qnan(FloatClass c)
}

/*
* Structure holding all of the decomposed parts of a float. The
* exponent is unbiased and the fraction is normalized. All
* calculations are done with a 64 bit fraction and then rounded as
* appropriate for the final format.
* Structure holding all of the decomposed parts of a float.
* The exponent is unbiased and the fraction is normalized.
*
* Thanks to the packed FloatClass a decent compiler should be able to
* fit the whole structure into registers and avoid using the stack
* for parameter passing.
* The fraction words are stored in big-endian word ordering,
* so that truncation from a larger format to a smaller format
* can be done simply by ignoring subsequent elements.
*/

typedef struct {
Expand All @@ -527,6 +525,15 @@ typedef struct {
};
} FloatParts64;

typedef struct {
FloatClass cls;
bool sign;
int32_t exp;
uint64_t frac_hi;
uint64_t frac_lo;
} FloatParts128;

/* These apply to the most significant word of each FloatPartsN. */
#define DECOMPOSED_BINARY_POINT 63
#define DECOMPOSED_IMPLICIT_BIT (1ull << DECOMPOSED_BINARY_POINT)

Expand Down Expand Up @@ -562,11 +569,11 @@ typedef struct {
.exp_bias = ((1 << E) - 1) >> 1, \
.exp_max = (1 << E) - 1, \
.frac_size = F, \
.frac_shift = DECOMPOSED_BINARY_POINT - F, \
.frac_lsb = 1ull << (DECOMPOSED_BINARY_POINT - F), \
.frac_lsbm1 = 1ull << ((DECOMPOSED_BINARY_POINT - F) - 1), \
.round_mask = (1ull << (DECOMPOSED_BINARY_POINT - F)) - 1, \
.roundeven_mask = (2ull << (DECOMPOSED_BINARY_POINT - F)) - 1
.frac_shift = (-F - 1) & 63, \
.frac_lsb = 1ull << ((-F - 1) & 63), \
.frac_lsbm1 = 1ull << ((-F - 2) & 63), \
.round_mask = (1ull << ((-F - 1) & 63)) - 1, \
.roundeven_mask = (2ull << ((-F - 1) & 63)) - 1

static const FloatFmt float16_params = {
FLOAT_PARAMS(5, 10)
Expand All @@ -589,6 +596,10 @@ static const FloatFmt float64_params = {
FLOAT_PARAMS(11, 52)
};

static const FloatFmt float128_params = {
FLOAT_PARAMS(15, 112)
};

/* Unpack a float to parts, but do not canonicalize. */
static void unpack_raw64(FloatParts64 *r, const FloatFmt *fmt, uint64_t raw)
{
Expand Down Expand Up @@ -623,6 +634,20 @@ static inline void float64_unpack_raw(FloatParts64 *p, float64 f)
unpack_raw64(p, &float64_params, f);
}

static void float128_unpack_raw(FloatParts128 *p, float128 f)
{
const int f_size = float128_params.frac_size - 64;
const int e_size = float128_params.exp_size;

*p = (FloatParts128) {
.cls = float_class_unclassified,
.sign = extract64(f.high, f_size + e_size, 1),
.exp = extract64(f.high, f_size, e_size),
.frac_hi = extract64(f.high, 0, f_size),
.frac_lo = f.low,
};
}

/* Pack a float from parts, but do not canonicalize. */
static uint64_t pack_raw64(const FloatParts64 *p, const FloatFmt *fmt)
{
Expand Down Expand Up @@ -656,6 +681,18 @@ static inline float64 float64_pack_raw(const FloatParts64 *p)
return make_float64(pack_raw64(p, &float64_params));
}

static float128 float128_pack_raw(const FloatParts128 *p)
{
const int f_size = float128_params.frac_size - 64;
const int e_size = float128_params.exp_size;
uint64_t hi;

hi = (uint64_t)p->sign << (f_size + e_size);
hi = deposit64(hi, f_size, e_size, p->exp);
hi = deposit64(hi, 0, f_size, p->frac_hi);
return make_float128(hi, p->frac_lo);
}

/*----------------------------------------------------------------------------
| Functions and definitions to determine: (1) whether tininess for underflow
| is detected before or after rounding by default, (2) what (if anything)
Expand All @@ -666,8 +703,30 @@ static inline float64 float64_pack_raw(const FloatParts64 *p)
*----------------------------------------------------------------------------*/
#include "softfloat-specialize.c.inc"

#define PARTS_GENERIC_64_128(NAME, P) \
QEMU_GENERIC(P, (FloatParts128 *, parts128_##NAME), parts64_##NAME)

#define parts_default_nan parts64_default_nan
#define parts_silence_nan parts64_silence_nan
#define parts_silence_nan(P, S) PARTS_GENERIC_64_128(silence_nan, P)(P, S)


/*
* Helper functions for softfloat-parts.c.inc, per-size operations.
*/

static void frac128_shl(FloatParts128 *a, int c)
{
shift128Left(a->frac_hi, a->frac_lo, c, &a->frac_hi, &a->frac_lo);
}

#define frac_shl(A, C) frac128_shl(A, C)

static void frac128_shr(FloatParts128 *a, int c)
{
shift128Right(a->frac_hi, a->frac_lo, c, &a->frac_hi, &a->frac_lo);
}

#define frac_shr(A, C) frac128_shr(A, C)

/* Canonicalize EXP and FRAC, setting CLS. */
static FloatParts64 sf_canonicalize(FloatParts64 part, const FloatFmt *parm,
Expand Down Expand Up @@ -3851,6 +3910,17 @@ bfloat16 bfloat16_silence_nan(bfloat16 a, float_status *status)
return bfloat16_pack_raw(&p);
}

float128 float128_silence_nan(float128 a, float_status *status)
{
FloatParts128 p;

float128_unpack_raw(&p, a);
frac_shl(&p, float128_params.frac_shift);
parts_silence_nan(&p, status);
frac_shr(&p, float128_params.frac_shift);
return float128_pack_raw(&p);
}

/*----------------------------------------------------------------------------
| If `a' is denormal and we are in flush-to-zero mode then set the
| input-denormal exception and return zero. Otherwise just return the value.
Expand Down

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