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softfloat: Move div_floats to softfloat-parts.c.inc

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Rename to parts$N_div.
Implement float128_div with FloatParts128.

Reviewed-by: Alex Bennée <alex.bennee@linaro.org>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
This commit is contained in:
Richard Henderson 2020-11-11 12:50:44 -08:00
parent 463e45dcb4
commit ec961b81b4
2 changed files with 171 additions and 174 deletions
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55
fpu/softfloat-parts.c.inc
View File

@ -539,3 +539,58 @@ static FloatPartsN *partsN(muladd)(FloatPartsN *a, FloatPartsN *b,
parts_default_nan(a, s);
return a;
}
/*
* Returns the result of dividing the floating-point value `a' by the
* corresponding value `b'. The operation is performed according to
* the IEC/IEEE Standard for Binary Floating-Point Arithmetic.
*/
static FloatPartsN *partsN(div)(FloatPartsN *a, FloatPartsN *b,
float_status *s)
{
int ab_mask = float_cmask(a->cls) | float_cmask(b->cls);
bool sign = a->sign ^ b->sign;
if (likely(ab_mask == float_cmask_normal)) {
a->sign = sign;
a->exp -= b->exp + frac_div(a, b);
return a;
}
/* 0/0 or Inf/Inf => NaN */
if (unlikely(ab_mask == float_cmask_zero) ||
unlikely(ab_mask == float_cmask_inf)) {
float_raise(float_flag_invalid, s);
parts_default_nan(a, s);
return a;
}
/* All the NaN cases */
if (unlikely(ab_mask & float_cmask_anynan)) {
return parts_pick_nan(a, b, s);
}
a->sign = sign;
/* Inf / X */
if (a->cls == float_class_inf) {
return a;
}
/* 0 / X */
if (a->cls == float_class_zero) {
return a;
}
/* X / Inf */
if (b->cls == float_class_inf) {
a->cls = float_class_zero;
return a;
}
/* X / 0 => Inf */
g_assert(b->cls == float_class_zero);
float_raise(float_flag_divbyzero, s);
a->cls = float_class_inf;
return a;
}

290
fpu/softfloat.c
View File

@ -803,6 +803,14 @@ static FloatParts128 *parts128_muladd(FloatParts128 *a, FloatParts128 *b,
#define parts_muladd(A, B, C, Z, S) \
PARTS_GENERIC_64_128(muladd, A)(A, B, C, Z, S)
static FloatParts64 *parts64_div(FloatParts64 *a, FloatParts64 *b,
float_status *s);
static FloatParts128 *parts128_div(FloatParts128 *a, FloatParts128 *b,
float_status *s);
#define parts_div(A, B, S) \
PARTS_GENERIC_64_128(div, A)(A, B, S)
/*
* Helper functions for softfloat-parts.c.inc, per-size operations.
*/
@ -895,6 +903,87 @@ static void frac128_clear(FloatParts128 *a)
#define frac_clear(A) FRAC_GENERIC_64_128(clear, A)(A)
static bool frac64_div(FloatParts64 *a, FloatParts64 *b)
{
uint64_t n1, n0, r, q;
bool ret;
/*
* We want a 2*N / N-bit division to produce exactly an N-bit
* result, so that we do not lose any precision and so that we
* do not have to renormalize afterward. If A.frac < B.frac,
* then division would produce an (N-1)-bit result; shift A left
* by one to produce the an N-bit result, and return true to
* decrement the exponent to match.
*
* The udiv_qrnnd algorithm that we're using requires normalization,
* i.e. the msb of the denominator must be set, which is already true.
*/
ret = a->frac < b->frac;
if (ret) {
n0 = a->frac;
n1 = 0;
} else {
n0 = a->frac >> 1;
n1 = a->frac << 63;
}
q = udiv_qrnnd(&r, n0, n1, b->frac);
/* Set lsb if there is a remainder, to set inexact. */
a->frac = q | (r != 0);
return ret;
}
static bool frac128_div(FloatParts128 *a, FloatParts128 *b)
{
uint64_t q0, q1, a0, a1, b0, b1;
uint64_t r0, r1, r2, r3, t0, t1, t2, t3;
bool ret = false;
a0 = a->frac_hi, a1 = a->frac_lo;
b0 = b->frac_hi, b1 = b->frac_lo;
ret = lt128(a0, a1, b0, b1);
if (!ret) {
a1 = shr_double(a0, a1, 1);
a0 = a0 >> 1;
}
/* Use 128/64 -> 64 division as estimate for 192/128 -> 128 division. */
q0 = estimateDiv128To64(a0, a1, b0);
/*
* Estimate is high because B1 was not included (unless B1 == 0).
* Reduce quotient and increase remainder until remainder is non-negative.
* This loop will execute 0 to 2 times.
*/
mul128By64To192(b0, b1, q0, &t0, &t1, &t2);
sub192(a0, a1, 0, t0, t1, t2, &r0, &r1, &r2);
while (r0 != 0) {
q0--;
add192(r0, r1, r2, 0, b0, b1, &r0, &r1, &r2);
}
/* Repeat using the remainder, producing a second word of quotient. */
q1 = estimateDiv128To64(r1, r2, b0);
mul128By64To192(b0, b1, q1, &t1, &t2, &t3);
sub192(r1, r2, 0, t1, t2, t3, &r1, &r2, &r3);
while (r1 != 0) {
q1--;
add192(r1, r2, r3, 0, b0, b1, &r1, &r2, &r3);
}
/* Any remainder indicates inexact; set sticky bit. */
q1 |= (r2 | r3) != 0;
a->frac_hi = q0;
a->frac_lo = q1;
return ret;
}
#define frac_div(A, B) FRAC_GENERIC_64_128(div, A)(A, B)
static bool frac64_eqz(FloatParts64 *a)
{
return a->frac == 0;
@ -1821,110 +1910,42 @@ float128 QEMU_FLATTEN float128_muladd(float128 a, float128 b, float128 c,
}
/*
* Returns the result of dividing the floating-point value `a' by the
* corresponding value `b'. The operation is performed according to
* the IEC/IEEE Standard for Binary Floating-Point Arithmetic.
* Division
*/
static FloatParts64 div_floats(FloatParts64 a, FloatParts64 b, float_status *s)
{
bool sign = a.sign ^ b.sign;
if (a.cls == float_class_normal && b.cls == float_class_normal) {
uint64_t n0, n1, q, r;
int exp = a.exp - b.exp;
/*
* We want a 2*N / N-bit division to produce exactly an N-bit
* result, so that we do not lose any precision and so that we
* do not have to renormalize afterward. If A.frac < B.frac,
* then division would produce an (N-1)-bit result; shift A left
* by one to produce the an N-bit result, and decrement the
* exponent to match.
*
* The udiv_qrnnd algorithm that we're using requires normalization,
* i.e. the msb of the denominator must be set, which is already true.
*/
if (a.frac < b.frac) {
exp -= 1;
shift128Left(0, a.frac, DECOMPOSED_BINARY_POINT + 1, &n1, &n0);
} else {
shift128Left(0, a.frac, DECOMPOSED_BINARY_POINT, &n1, &n0);
}
q = udiv_qrnnd(&r, n1, n0, b.frac);
/* Set lsb if there is a remainder, to set inexact. */
a.frac = q | (r != 0);
a.sign = sign;
a.exp = exp;
return a;
}
/* handle all the NaN cases */
if (is_nan(a.cls) || is_nan(b.cls)) {
return *parts_pick_nan(&a, &b, s);
}
/* 0/0 or Inf/Inf */
if (a.cls == b.cls
&&
(a.cls == float_class_inf || a.cls == float_class_zero)) {
float_raise(float_flag_invalid, s);
parts_default_nan(&a, s);
return a;
}
/* Inf / x or 0 / x */
if (a.cls == float_class_inf || a.cls == float_class_zero) {
a.sign = sign;
return a;
}
/* Div 0 => Inf */
if (b.cls == float_class_zero) {
float_raise(float_flag_divbyzero, s);
a.cls = float_class_inf;
a.sign = sign;
return a;
}
/* Div by Inf */
if (b.cls == float_class_inf) {
a.cls = float_class_zero;
a.sign = sign;
return a;
}
g_assert_not_reached();
}
float16 float16_div(float16 a, float16 b, float_status *status)
{
FloatParts64 pa, pb, pr;
FloatParts64 pa, pb, *pr;
float16_unpack_canonical(&pa, a, status);
float16_unpack_canonical(&pb, b, status);
pr = div_floats(pa, pb, status);
pr = parts_div(&pa, &pb, status);
return float16_round_pack_canonical(&pr, status);
return float16_round_pack_canonical(pr, status);
}
static float32 QEMU_SOFTFLOAT_ATTR
soft_f32_div(float32 a, float32 b, float_status *status)
{
FloatParts64 pa, pb, pr;
FloatParts64 pa, pb, *pr;
float32_unpack_canonical(&pa, a, status);
float32_unpack_canonical(&pb, b, status);
pr = div_floats(pa, pb, status);
pr = parts_div(&pa, &pb, status);
return float32_round_pack_canonical(&pr, status);
return float32_round_pack_canonical(pr, status);
}
static float64 QEMU_SOFTFLOAT_ATTR
soft_f64_div(float64 a, float64 b, float_status *status)
{
FloatParts64 pa, pb, pr;
FloatParts64 pa, pb, *pr;
float64_unpack_canonical(&pa, a, status);
float64_unpack_canonical(&pb, b, status);
pr = div_floats(pa, pb, status);
pr = parts_div(&pa, &pb, status);
return float64_round_pack_canonical(&pr, status);
return float64_round_pack_canonical(pr, status);
}
static float hard_f32_div(float a, float b)
@ -1985,20 +2006,28 @@ float64_div(float64 a, float64 b, float_status *s)
f64_div_pre, f64_div_post);
}
/*
* Returns the result of dividing the bfloat16
* value `a' by the corresponding value `b'.
*/
bfloat16 bfloat16_div(bfloat16 a, bfloat16 b, float_status *status)
bfloat16 QEMU_FLATTEN
bfloat16_div(bfloat16 a, bfloat16 b, float_status *status)
{
FloatParts64 pa, pb, pr;
FloatParts64 pa, pb, *pr;
bfloat16_unpack_canonical(&pa, a, status);
bfloat16_unpack_canonical(&pb, b, status);
pr = div_floats(pa, pb, status);
pr = parts_div(&pa, &pb, status);
return bfloat16_round_pack_canonical(&pr, status);
return bfloat16_round_pack_canonical(pr, status);
}
float128 QEMU_FLATTEN
float128_div(float128 a, float128 b, float_status *status)
{
FloatParts128 pa, pb, *pr;
float128_unpack_canonical(&pa, a, status);
float128_unpack_canonical(&pb, b, status);
pr = parts_div(&pa, &pb, status);
return float128_round_pack_canonical(pr, status);
}
/*
@ -7123,93 +7152,6 @@ float128 float128_round_to_int(float128 a, float_status *status)
}
/*----------------------------------------------------------------------------
| Returns the result of dividing the quadruple-precision floating-point value
| `a' by the corresponding value `b'. The operation is performed according to
| the IEC/IEEE Standard for Binary Floating-Point Arithmetic.
*----------------------------------------------------------------------------*/
float128 float128_div(float128 a, float128 b, float_status *status)
{
bool aSign, bSign, zSign;
int32_t aExp, bExp, zExp;
uint64_t aSig0, aSig1, bSig0, bSig1, zSig0, zSig1, zSig2;
uint64_t rem0, rem1, rem2, rem3, term0, term1, term2, term3;
aSig1 = extractFloat128Frac1( a );
aSig0 = extractFloat128Frac0( a );
aExp = extractFloat128Exp( a );
aSign = extractFloat128Sign( a );
bSig1 = extractFloat128Frac1( b );
bSig0 = extractFloat128Frac0( b );
bExp = extractFloat128Exp( b );
bSign = extractFloat128Sign( b );
zSign = aSign ^ bSign;
if ( aExp == 0x7FFF ) {
if (aSig0 | aSig1) {
return propagateFloat128NaN(a, b, status);
}
if ( bExp == 0x7FFF ) {
if (bSig0 | bSig1) {
return propagateFloat128NaN(a, b, status);
}
goto invalid;
}
return packFloat128( zSign, 0x7FFF, 0, 0 );
}
if ( bExp == 0x7FFF ) {
if (bSig0 | bSig1) {
return propagateFloat128NaN(a, b, status);
}
return packFloat128( zSign, 0, 0, 0 );
}
if ( bExp == 0 ) {
if ( ( bSig0 | bSig1 ) == 0 ) {
if ( ( aExp | aSig0 | aSig1 ) == 0 ) {
invalid:
float_raise(float_flag_invalid, status);
return float128_default_nan(status);
}
float_raise(float_flag_divbyzero, status);
return packFloat128( zSign, 0x7FFF, 0, 0 );
}
normalizeFloat128Subnormal( bSig0, bSig1, &bExp, &bSig0, &bSig1 );
}
if ( aExp == 0 ) {
if ( ( aSig0 | aSig1 ) == 0 ) return packFloat128( zSign, 0, 0, 0 );
normalizeFloat128Subnormal( aSig0, aSig1, &aExp, &aSig0, &aSig1 );
}
zExp = aExp - bExp + 0x3FFD;
shortShift128Left(
aSig0 | UINT64_C(0x0001000000000000), aSig1, 15, &aSig0, &aSig1 );
shortShift128Left(
bSig0 | UINT64_C(0x0001000000000000), bSig1, 15, &bSig0, &bSig1 );
if ( le128( bSig0, bSig1, aSig0, aSig1 ) ) {
shift128Right( aSig0, aSig1, 1, &aSig0, &aSig1 );
++zExp;
}
zSig0 = estimateDiv128To64( aSig0, aSig1, bSig0 );
mul128By64To192( bSig0, bSig1, zSig0, &term0, &term1, &term2 );
sub192( aSig0, aSig1, 0, term0, term1, term2, &rem0, &rem1, &rem2 );
while ( (int64_t) rem0 < 0 ) {
--zSig0;
add192( rem0, rem1, rem2, 0, bSig0, bSig1, &rem0, &rem1, &rem2 );
}
zSig1 = estimateDiv128To64( rem1, rem2, bSig0 );
if ( ( zSig1 & 0x3FFF ) <= 4 ) {
mul128By64To192( bSig0, bSig1, zSig1, &term1, &term2, &term3 );
sub192( rem1, rem2, 0, term1, term2, term3, &rem1, &rem2, &rem3 );
while ( (int64_t) rem1 < 0 ) {
--zSig1;
add192( rem1, rem2, rem3, 0, bSig0, bSig1, &rem1, &rem2, &rem3 );
}
zSig1 |= ( ( rem1 | rem2 | rem3 ) != 0 );
}
shift128ExtraRightJamming( zSig0, zSig1, 0, 15, &zSig0, &zSig1, &zSig2 );
return roundAndPackFloat128(zSign, zExp, zSig0, zSig1, zSig2, status);
}
/*----------------------------------------------------------------------------
| Returns the remainder of the quadruple-precision floating-point value `a'
| with respect to the corresponding value `b'. The operation is performed