From dbe4d53a590f5689772b683984588b3cf6df163e Mon Sep 17 00:00:00 2001 From: =?UTF-8?q?Alex=20Benn=C3=A9e?= Date: Wed, 29 Nov 2017 10:21:25 +0000 Subject: [PATCH] fpu/softfloat: re-factor round_to_int MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit We can now add float16_round_to_int and use the common round_decomposed and canonicalize functions to have a single implementation for float16/32/64 round_to_int functions. Signed-off-by: Alex Bennée Signed-off-by: Richard Henderson Reviewed-by: Peter Maydell --- fpu/softfloat.c | 319 ++++++++++++++++++---------------------- include/fpu/softfloat.h | 1 + 2 files changed, 146 insertions(+), 174 deletions(-) diff --git a/fpu/softfloat.c b/fpu/softfloat.c index ae4ba6de51..616c6cef07 100644 --- a/fpu/softfloat.c +++ b/fpu/softfloat.c @@ -560,6 +560,25 @@ static bool is_qnan(FloatClass c) return c == float_class_qnan; } +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; + /* fall through */ + case float_class_qnan: + if (s->default_nan_mode) { + a.cls = float_class_dnan; + } + break; + + default: + g_assert_not_reached(); + } + return a; +} + static FloatParts pick_nan(FloatParts a, FloatParts b, float_status *s) { if (is_snan(a.cls) || is_snan(b.cls)) { @@ -1175,6 +1194,132 @@ float64 float64_div(float64 a, float64 b, float_status *status) return float64_round_pack_canonical(pr, status); } +/* + * Rounds the floating-point value `a' to an integer, and returns the + * result as a floating-point value. The operation is performed + * according to the IEC/IEEE Standard for Binary Floating-Point + * Arithmetic. + */ + +static FloatParts round_to_int(FloatParts a, int rounding_mode, float_status *s) +{ + if (is_nan(a.cls)) { + return return_nan(a, s); + } + + switch (a.cls) { + case float_class_zero: + case float_class_inf: + case float_class_qnan: + /* already "integral" */ + break; + case float_class_normal: + if (a.exp >= DECOMPOSED_BINARY_POINT) { + /* already integral */ + break; + } + if (a.exp < 0) { + bool one; + /* all fractional */ + s->float_exception_flags |= float_flag_inexact; + switch (rounding_mode) { + case float_round_nearest_even: + one = a.exp == -1 && a.frac > DECOMPOSED_IMPLICIT_BIT; + break; + case float_round_ties_away: + one = a.exp == -1 && a.frac >= DECOMPOSED_IMPLICIT_BIT; + break; + case float_round_to_zero: + one = false; + break; + case float_round_up: + one = !a.sign; + break; + case float_round_down: + one = a.sign; + break; + default: + g_assert_not_reached(); + } + + if (one) { + a.frac = DECOMPOSED_IMPLICIT_BIT; + a.exp = 0; + } else { + a.cls = float_class_zero; + } + } else { + uint64_t frac_lsb = DECOMPOSED_IMPLICIT_BIT >> a.exp; + uint64_t frac_lsbm1 = frac_lsb >> 1; + uint64_t rnd_even_mask = (frac_lsb - 1) | frac_lsb; + uint64_t rnd_mask = rnd_even_mask >> 1; + uint64_t inc; + + switch (rounding_mode) { + case float_round_nearest_even: + inc = ((a.frac & rnd_even_mask) != frac_lsbm1 ? frac_lsbm1 : 0); + break; + case float_round_ties_away: + inc = frac_lsbm1; + break; + case float_round_to_zero: + inc = 0; + break; + case float_round_up: + inc = a.sign ? 0 : rnd_mask; + break; + case float_round_down: + inc = a.sign ? rnd_mask : 0; + break; + default: + g_assert_not_reached(); + } + + if (a.frac & rnd_mask) { + s->float_exception_flags |= float_flag_inexact; + a.frac += inc; + a.frac &= ~rnd_mask; + if (a.frac & DECOMPOSED_OVERFLOW_BIT) { + a.frac >>= 1; + a.exp++; + } + } + } + break; + default: + g_assert_not_reached(); + } + return a; +} + +float16 float16_round_to_int(float16 a, float_status *s) +{ + FloatParts pa = float16_unpack_canonical(a, s); + FloatParts pr = round_to_int(pa, s->float_rounding_mode, s); + return float16_round_pack_canonical(pr, s); +} + +float32 float32_round_to_int(float32 a, float_status *s) +{ + FloatParts pa = float32_unpack_canonical(a, s); + FloatParts pr = round_to_int(pa, s->float_rounding_mode, s); + return float32_round_pack_canonical(pr, s); +} + +float64 float64_round_to_int(float64 a, float_status *s) +{ + FloatParts pa = float64_unpack_canonical(a, s); + FloatParts pr = round_to_int(pa, s->float_rounding_mode, s); + return float64_round_pack_canonical(pr, s); +} + +float64 float64_trunc_to_int(float64 a, float_status *s) +{ + FloatParts pa = float64_unpack_canonical(a, s); + FloatParts pr = round_to_int(pa, float_round_to_zero, s); + return float64_round_pack_canonical(pr, s); +} + /*---------------------------------------------------------------------------- | Takes a 64-bit fixed-point value `absZ' with binary point between bits 6 | and 7, and returns the properly rounded 32-bit integer corresponding to the @@ -2905,87 +3050,6 @@ float128 float32_to_float128(float32 a, float_status *status) } -/*---------------------------------------------------------------------------- -| Rounds the single-precision floating-point value `a' to an integer, and -| returns the result as a single-precision floating-point value. The -| operation is performed according to the IEC/IEEE Standard for Binary -| Floating-Point Arithmetic. -*----------------------------------------------------------------------------*/ - -float32 float32_round_to_int(float32 a, float_status *status) -{ - flag aSign; - int aExp; - uint32_t lastBitMask, roundBitsMask; - uint32_t z; - a = float32_squash_input_denormal(a, status); - - aExp = extractFloat32Exp( a ); - if ( 0x96 <= aExp ) { - if ( ( aExp == 0xFF ) && extractFloat32Frac( a ) ) { - return propagateFloat32NaN(a, a, status); - } - return a; - } - if ( aExp <= 0x7E ) { - if ( (uint32_t) ( float32_val(a)<<1 ) == 0 ) return a; - status->float_exception_flags |= float_flag_inexact; - aSign = extractFloat32Sign( a ); - switch (status->float_rounding_mode) { - case float_round_nearest_even: - if ( ( aExp == 0x7E ) && extractFloat32Frac( a ) ) { - return packFloat32( aSign, 0x7F, 0 ); - } - break; - case float_round_ties_away: - if (aExp == 0x7E) { - return packFloat32(aSign, 0x7F, 0); - } - break; - case float_round_down: - return make_float32(aSign ? 0xBF800000 : 0); - case float_round_up: - return make_float32(aSign ? 0x80000000 : 0x3F800000); - } - return packFloat32( aSign, 0, 0 ); - } - lastBitMask = 1; - lastBitMask <<= 0x96 - aExp; - roundBitsMask = lastBitMask - 1; - z = float32_val(a); - switch (status->float_rounding_mode) { - case float_round_nearest_even: - z += lastBitMask>>1; - if ((z & roundBitsMask) == 0) { - z &= ~lastBitMask; - } - break; - case float_round_ties_away: - z += lastBitMask >> 1; - break; - case float_round_to_zero: - break; - case float_round_up: - if (!extractFloat32Sign(make_float32(z))) { - z += roundBitsMask; - } - break; - case float_round_down: - if (extractFloat32Sign(make_float32(z))) { - z += roundBitsMask; - } - break; - default: - abort(); - } - z &= ~ roundBitsMask; - if (z != float32_val(a)) { - status->float_exception_flags |= float_flag_inexact; - } - return make_float32(z); - -} - /*---------------------------------------------------------------------------- | Returns the remainder of the single-precision floating-point value `a' | with respect to the corresponding value `b'. The operation is performed @@ -4129,99 +4193,6 @@ float128 float64_to_float128(float64 a, float_status *status) } -/*---------------------------------------------------------------------------- -| Rounds the double-precision floating-point value `a' to an integer, and -| returns the result as a double-precision floating-point value. The -| operation is performed according to the IEC/IEEE Standard for Binary -| Floating-Point Arithmetic. -*----------------------------------------------------------------------------*/ - -float64 float64_round_to_int(float64 a, float_status *status) -{ - flag aSign; - int aExp; - uint64_t lastBitMask, roundBitsMask; - uint64_t z; - a = float64_squash_input_denormal(a, status); - - aExp = extractFloat64Exp( a ); - if ( 0x433 <= aExp ) { - if ( ( aExp == 0x7FF ) && extractFloat64Frac( a ) ) { - return propagateFloat64NaN(a, a, status); - } - return a; - } - if ( aExp < 0x3FF ) { - if ( (uint64_t) ( float64_val(a)<<1 ) == 0 ) return a; - status->float_exception_flags |= float_flag_inexact; - aSign = extractFloat64Sign( a ); - switch (status->float_rounding_mode) { - case float_round_nearest_even: - if ( ( aExp == 0x3FE ) && extractFloat64Frac( a ) ) { - return packFloat64( aSign, 0x3FF, 0 ); - } - break; - case float_round_ties_away: - if (aExp == 0x3FE) { - return packFloat64(aSign, 0x3ff, 0); - } - break; - case float_round_down: - return make_float64(aSign ? LIT64( 0xBFF0000000000000 ) : 0); - case float_round_up: - return make_float64( - aSign ? LIT64( 0x8000000000000000 ) : LIT64( 0x3FF0000000000000 )); - } - return packFloat64( aSign, 0, 0 ); - } - lastBitMask = 1; - lastBitMask <<= 0x433 - aExp; - roundBitsMask = lastBitMask - 1; - z = float64_val(a); - switch (status->float_rounding_mode) { - case float_round_nearest_even: - z += lastBitMask >> 1; - if ((z & roundBitsMask) == 0) { - z &= ~lastBitMask; - } - break; - case float_round_ties_away: - z += lastBitMask >> 1; - break; - case float_round_to_zero: - break; - case float_round_up: - if (!extractFloat64Sign(make_float64(z))) { - z += roundBitsMask; - } - break; - case float_round_down: - if (extractFloat64Sign(make_float64(z))) { - z += roundBitsMask; - } - break; - default: - abort(); - } - z &= ~ roundBitsMask; - if (z != float64_val(a)) { - status->float_exception_flags |= float_flag_inexact; - } - return make_float64(z); - -} - -float64 float64_trunc_to_int(float64 a, float_status *status) -{ - int oldmode; - float64 res; - oldmode = status->float_rounding_mode; - status->float_rounding_mode = float_round_to_zero; - res = float64_round_to_int(a, status); - status->float_rounding_mode = oldmode; - return res; -} - /*---------------------------------------------------------------------------- | Returns the remainder of the double-precision floating-point value `a' diff --git a/include/fpu/softfloat.h b/include/fpu/softfloat.h index 65bc7442d2..4650758c23 100644 --- a/include/fpu/softfloat.h +++ b/include/fpu/softfloat.h @@ -237,6 +237,7 @@ float64 float16_to_float64(float16 a, flag ieee, float_status *status); | Software half-precision operations. *----------------------------------------------------------------------------*/ +float16 float16_round_to_int(float16, float_status *status); float16 float16_add(float16, float16, float_status *status); float16 float16_sub(float16, float16, float_status *status); float16 float16_mul(float16, float16, float_status *status);