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Re: [Qemu-devel] [PATCH v2] softfloat: Support float_round_to_odd more p
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From: |
Alex Bennée |
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Subject: |
Re: [Qemu-devel] [PATCH v2] softfloat: Support float_round_to_odd more places |
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Date: |
Fri, 22 Feb 2019 20:07:58 +0000 |
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User-agent: |
mu4e 1.1.0; emacs 26.1 |
Richard Henderson <address@hidden> writes:
> Previously this was only supported for roundAndPackFloat64.
>
> New support in round_canonical, round_to_int, float128_round_to_int,
> roundAndPackFloat32, roundAndPackInt32, roundAndPackInt64,
> roundAndPackUint64. This does not include any of the floatx80 routines,
> as we do not have users for that rounding mode there.
>
> Signed-off-by: Richard Henderson <address@hidden>
Queued to fpu/next, thanks.
> ---
> v2: Convert float128_round_to_int as well. Add fp-test support.
> ---
> fpu/softfloat.c | 64 ++++++++++++++++++++++++++++++++++++++++++----
> tests/fp/fp-test.c | 43 ++++++++++++++++++++++++-------
> 2 files changed, 93 insertions(+), 14 deletions(-)
>
> diff --git a/fpu/softfloat.c b/fpu/softfloat.c
> index 9132d7a0b0..76132d4cd5 100644
> --- a/fpu/softfloat.c
> +++ b/fpu/softfloat.c
> @@ -696,6 +696,7 @@ static FloatParts sf_canonicalize(FloatParts part, const
> FloatFmt *parm,
> static FloatParts round_canonical(FloatParts p, float_status *s,
> const FloatFmt *parm)
> {
> + const uint64_t frac_lsb = parm->frac_lsb;
> const uint64_t frac_lsbm1 = parm->frac_lsbm1;
> const uint64_t round_mask = parm->round_mask;
> const uint64_t roundeven_mask = parm->roundeven_mask;
> @@ -731,6 +732,10 @@ static FloatParts round_canonical(FloatParts p,
> float_status *s,
> inc = p.sign ? round_mask : 0;
> overflow_norm = !p.sign;
> break;
> + case float_round_to_odd:
> + overflow_norm = true;
> + inc = frac & frac_lsb ? 0 : round_mask;
> + break;
> default:
> g_assert_not_reached();
> }
> @@ -778,9 +783,14 @@ static FloatParts round_canonical(FloatParts p,
> float_status *s,
> shift64RightJamming(frac, 1 - exp, &frac);
> if (frac & round_mask) {
> /* Need to recompute round-to-even. */
> - if (s->float_rounding_mode == float_round_nearest_even) {
> + switch (s->float_rounding_mode) {
> + case float_round_nearest_even:
> inc = ((frac & roundeven_mask) != frac_lsbm1
> ? frac_lsbm1 : 0);
> + break;
> + case float_round_to_odd:
> + inc = frac & frac_lsb ? 0 : round_mask;
> + break;
> }
> flags |= float_flag_inexact;
> frac += inc;
> @@ -1988,6 +1998,9 @@ static FloatParts round_to_int(FloatParts a, int rmode,
> case float_round_down:
> one = a.sign;
> break;
> + case float_round_to_odd:
> + one = true;
> + break;
> default:
> g_assert_not_reached();
> }
> @@ -2021,6 +2034,9 @@ static FloatParts round_to_int(FloatParts a, int rmode,
> case float_round_down:
> inc = a.sign ? rnd_mask : 0;
> break;
> + case float_round_to_odd:
> + inc = a.frac & frac_lsb ? 0 : rnd_mask;
> + break;
> default:
> g_assert_not_reached();
> }
> @@ -3314,6 +3330,9 @@ static int32_t roundAndPackInt32(flag zSign, uint64_t
> absZ, float_status *status
> case float_round_down:
> roundIncrement = zSign ? 0x7f : 0;
> break;
> + case float_round_to_odd:
> + roundIncrement = absZ & 0x80 ? 0 : 0x7f;
> + break;
> default:
> abort();
> }
> @@ -3368,6 +3387,9 @@ static int64_t roundAndPackInt64(flag zSign, uint64_t
> absZ0, uint64_t absZ1,
> case float_round_down:
> increment = zSign && absZ1;
> break;
> + case float_round_to_odd:
> + increment = !(absZ0 & 1) && absZ1;
> + break;
> default:
> abort();
> }
> @@ -3424,6 +3446,9 @@ static int64_t roundAndPackUint64(flag zSign, uint64_t
> absZ0,
> case float_round_down:
> increment = zSign && absZ1;
> break;
> + case float_round_to_odd:
> + increment = !(absZ0 & 1) && absZ1;
> + break;
> default:
> abort();
> }
> @@ -3526,6 +3551,8 @@ static float32 roundAndPackFloat32(flag zSign, int
> zExp, uint32_t zSig,
> case float_round_down:
> roundIncrement = zSign ? 0x7f : 0;
> break;
> + case float_round_to_odd:
> + roundIncrement = zSig & 0x80 ? 0 : 0x7f;
> default:
> abort();
> break;
> @@ -3536,8 +3563,10 @@ static float32 roundAndPackFloat32(flag zSign, int
> zExp, uint32_t zSig,
> || ( ( zExp == 0xFD )
> && ( (int32_t) ( zSig + roundIncrement ) < 0 ) )
> ) {
> + bool overflow_to_inf = roundingMode != float_round_to_odd &&
> + roundIncrement != 0;
> float_raise(float_flag_overflow | float_flag_inexact, status);
> - return packFloat32( zSign, 0xFF, - ( roundIncrement == 0 ));
> + return packFloat32(zSign, 0xFF, -!overflow_to_inf);
> }
> if ( zExp < 0 ) {
> if (status->flush_to_zero) {
> @@ -3555,6 +3584,13 @@ static float32 roundAndPackFloat32(flag zSign, int
> zExp, uint32_t zSig,
> if (isTiny && roundBits) {
> float_raise(float_flag_underflow, status);
> }
> + if (roundingMode == float_round_to_odd) {
> + /*
> + * For round-to-odd case, the roundIncrement depends on
> + * zSig which just changed.
> + */
> + roundIncrement = zSig & 0x80 ? 0 : 0x7f;
> + }
> }
> }
> if (roundBits) {
> @@ -6958,6 +6994,15 @@ float128 float128_round_to_int(float128 a,
> float_status *status)
> add128(z.high, z.low, 0, roundBitsMask, &z.high, &z.low);
> }
> break;
> + case float_round_to_odd:
> + /*
> + * Note that if lastBitMask == 0, the last bit is the lsb
> + * of high, and roundBitsMask == -1.
> + */
> + if ((lastBitMask ? z.low & lastBitMask : z.high & 1) == 0) {
> + add128(z.high, z.low, 0, roundBitsMask, &z.high, &z.low);
> + }
> + break;
> default:
> abort();
> }
> @@ -6969,7 +7014,7 @@ float128 float128_round_to_int(float128 a, float_status
> *status)
> status->float_exception_flags |= float_flag_inexact;
> aSign = extractFloat128Sign( a );
> switch (status->float_rounding_mode) {
> - case float_round_nearest_even:
> + case float_round_nearest_even:
> if ( ( aExp == 0x3FFE )
> && ( extractFloat128Frac0( a )
> | extractFloat128Frac1( a ) )
> @@ -6982,14 +7027,17 @@ float128 float128_round_to_int(float128 a,
> float_status *status)
> return packFloat128(aSign, 0x3FFF, 0, 0);
> }
> break;
> - case float_round_down:
> + case float_round_down:
> return
> aSign ? packFloat128( 1, 0x3FFF, 0, 0 )
> : packFloat128( 0, 0, 0, 0 );
> - case float_round_up:
> + case float_round_up:
> return
> aSign ? packFloat128( 1, 0, 0, 0 )
> : packFloat128( 0, 0x3FFF, 0, 0 );
> +
> + case float_round_to_odd:
> + return packFloat128(aSign, 0x3FFF, 0, 0);
> }
> return packFloat128( aSign, 0, 0, 0 );
> }
> @@ -7022,6 +7070,12 @@ float128 float128_round_to_int(float128 a,
> float_status *status)
> z.high += roundBitsMask;
> }
> break;
> + case float_round_to_odd:
> + if ((z.high & lastBitMask) == 0) {
> + z.high |= (a.low != 0);
> + z.high += roundBitsMask;
> + }
> + break;
> default:
> abort();
> }
> diff --git a/tests/fp/fp-test.c b/tests/fp/fp-test.c
> index 2a35ef601d..471adb862d 100644
> --- a/tests/fp/fp-test.c
> +++ b/tests/fp/fp-test.c
> @@ -125,17 +125,42 @@ static void not_implemented(void)
>
> static bool blacklisted(unsigned op, int rmode)
> {
> - /* odd has only been implemented for a few 128-bit ops */
> + /* odd has not been implemented for any 80-bit ops */
> if (rmode == softfloat_round_odd) {
> switch (op) {
> - case F128_ADD:
> - case F128_SUB:
> - case F128_MUL:
> - case F128_DIV:
> - case F128_TO_F64:
> - case F128_SQRT:
> - return false;
> - default:
> + case EXTF80_TO_UI32:
> + case EXTF80_TO_UI64:
> + case EXTF80_TO_I32:
> + case EXTF80_TO_I64:
> + case EXTF80_TO_UI32_R_MINMAG:
> + case EXTF80_TO_UI64_R_MINMAG:
> + case EXTF80_TO_I32_R_MINMAG:
> + case EXTF80_TO_I64_R_MINMAG:
> + case EXTF80_TO_F16:
> + case EXTF80_TO_F32:
> + case EXTF80_TO_F64:
> + case EXTF80_TO_F128:
> + case EXTF80_ROUNDTOINT:
> + case EXTF80_ADD:
> + case EXTF80_SUB:
> + case EXTF80_MUL:
> + case EXTF80_DIV:
> + case EXTF80_REM:
> + case EXTF80_SQRT:
> + case EXTF80_EQ:
> + case EXTF80_LE:
> + case EXTF80_LT:
> + case EXTF80_EQ_SIGNALING:
> + case EXTF80_LE_QUIET:
> + case EXTF80_LT_QUIET:
> + case UI32_TO_EXTF80:
> + case UI64_TO_EXTF80:
> + case I32_TO_EXTF80:
> + case I64_TO_EXTF80:
> + case F16_TO_EXTF80:
> + case F32_TO_EXTF80:
> + case F64_TO_EXTF80:
> + case F128_TO_EXTF80:
> return true;
> }
> }
--
Alex Bennée