diff options
Diffstat (limited to 'fpu/softfloat.c')
| -rw-r--r-- | fpu/softfloat.c | 488 |
1 files changed, 118 insertions, 370 deletions
diff --git a/fpu/softfloat.c b/fpu/softfloat.c index 64e1ad4f98..55e6701f26 100644 --- a/fpu/softfloat.c +++ b/fpu/softfloat.c @@ -114,15 +114,6 @@ static inline int extractFloat16Exp(float16 a) } /*---------------------------------------------------------------------------- -| Returns the sign bit of the single-precision floating-point value `a'. -*----------------------------------------------------------------------------*/ - -static inline flag extractFloat16Sign(float16 a) -{ - return float16_val(a)>>15; -} - -/*---------------------------------------------------------------------------- | Returns the fraction bits of the single-precision floating-point value `a'. *----------------------------------------------------------------------------*/ @@ -254,6 +245,11 @@ static const FloatFmt float16_params = { FLOAT_PARAMS(5, 10) }; +static const FloatFmt float16_params_ahp = { + FLOAT_PARAMS(5, 10), + .arm_althp = true +}; + static const FloatFmt float32_params = { FLOAT_PARAMS(8, 23) }; @@ -497,14 +493,27 @@ static FloatParts round_canonical(FloatParts p, float_status *s, return p; } +/* Explicit FloatFmt version */ +static FloatParts float16a_unpack_canonical(float16 f, float_status *s, + const FloatFmt *params) +{ + return canonicalize(float16_unpack_raw(f), params, s); +} + static FloatParts float16_unpack_canonical(float16 f, float_status *s) { - return canonicalize(float16_unpack_raw(f), &float16_params, s); + return float16a_unpack_canonical(f, s, &float16_params); +} + +static float16 float16a_round_pack_canonical(FloatParts p, float_status *s, + const FloatFmt *params) +{ + return float16_pack_raw(round_canonical(p, s, params)); } static float16 float16_round_pack_canonical(FloatParts p, float_status *s) { - return float16_pack_raw(round_canonical(p, s, &float16_params)); + return float16a_round_pack_canonical(p, s, &float16_params); } static FloatParts float32_unpack_canonical(float32 f, float_status *s) @@ -1182,6 +1191,104 @@ float64 float64_div(float64 a, float64 b, float_status *status) } /* + * Float to Float conversions + * + * Returns the result of converting one float format to another. The + * conversion is performed according to the IEC/IEEE Standard for + * Binary Floating-Point Arithmetic. + * + * The float_to_float helper only needs to take care of raising + * invalid exceptions and handling the conversion on NaNs. + */ + +static FloatParts float_to_float(FloatParts a, const FloatFmt *dstf, + float_status *s) +{ + if (dstf->arm_althp) { + switch (a.cls) { + case float_class_qnan: + case float_class_snan: + /* There is no NaN in the destination format. Raise Invalid + * and return a zero with the sign of the input NaN. + */ + s->float_exception_flags |= float_flag_invalid; + a.cls = float_class_zero; + a.frac = 0; + a.exp = 0; + break; + + case float_class_inf: + /* There is no Inf in the destination format. Raise Invalid + * and return the maximum normal with the correct sign. + */ + s->float_exception_flags |= float_flag_invalid; + a.cls = float_class_normal; + a.exp = dstf->exp_max; + a.frac = ((1ull << dstf->frac_size) - 1) << dstf->frac_shift; + break; + + default: + break; + } + } else if (is_nan(a.cls)) { + if (is_snan(a.cls)) { + s->float_exception_flags |= float_flag_invalid; + a = parts_silence_nan(a, s); + } + if (s->default_nan_mode) { + return parts_default_nan(s); + } + } + return a; +} + +float32 float16_to_float32(float16 a, bool ieee, float_status *s) +{ + const FloatFmt *fmt16 = ieee ? &float16_params : &float16_params_ahp; + FloatParts p = float16a_unpack_canonical(a, s, fmt16); + FloatParts pr = float_to_float(p, &float32_params, s); + return float32_round_pack_canonical(pr, s); +} + +float64 float16_to_float64(float16 a, bool ieee, float_status *s) +{ + const FloatFmt *fmt16 = ieee ? &float16_params : &float16_params_ahp; + FloatParts p = float16a_unpack_canonical(a, s, fmt16); + FloatParts pr = float_to_float(p, &float64_params, s); + return float64_round_pack_canonical(pr, s); +} + +float16 float32_to_float16(float32 a, bool ieee, float_status *s) +{ + const FloatFmt *fmt16 = ieee ? &float16_params : &float16_params_ahp; + FloatParts p = float32_unpack_canonical(a, s); + FloatParts pr = float_to_float(p, fmt16, s); + return float16a_round_pack_canonical(pr, s, fmt16); +} + +float64 float32_to_float64(float32 a, float_status *s) +{ + FloatParts p = float32_unpack_canonical(a, s); + FloatParts pr = float_to_float(p, &float64_params, s); + return float64_round_pack_canonical(pr, s); +} + +float16 float64_to_float16(float64 a, bool ieee, float_status *s) +{ + const FloatFmt *fmt16 = ieee ? &float16_params : &float16_params_ahp; + FloatParts p = float64_unpack_canonical(a, s); + FloatParts pr = float_to_float(p, fmt16, s); + return float16a_round_pack_canonical(pr, s, fmt16); +} + +float32 float64_to_float32(float64 a, float_status *s) +{ + FloatParts p = float64_unpack_canonical(a, s); + FloatParts pr = float_to_float(p, &float32_params, s); + return float32_round_pack_canonical(pr, s); +} + +/* * 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 @@ -3124,41 +3231,6 @@ float128 uint64_to_float128(uint64_t a, float_status *status) return normalizeRoundAndPackFloat128(0, 0x406E, 0, a, status); } - - - -/*---------------------------------------------------------------------------- -| Returns the result of converting the single-precision floating-point value -| `a' to the double-precision floating-point format. The conversion is -| performed according to the IEC/IEEE Standard for Binary Floating-Point -| Arithmetic. -*----------------------------------------------------------------------------*/ - -float64 float32_to_float64(float32 a, float_status *status) -{ - flag aSign; - int aExp; - uint32_t aSig; - a = float32_squash_input_denormal(a, status); - - aSig = extractFloat32Frac( a ); - aExp = extractFloat32Exp( a ); - aSign = extractFloat32Sign( a ); - if ( aExp == 0xFF ) { - if (aSig) { - return commonNaNToFloat64(float32ToCommonNaN(a, status), status); - } - return packFloat64( aSign, 0x7FF, 0 ); - } - if ( aExp == 0 ) { - if ( aSig == 0 ) return packFloat64( aSign, 0, 0 ); - normalizeFloat32Subnormal( aSig, &aExp, &aSig ); - --aExp; - } - return packFloat64( aSign, aExp + 0x380, ( (uint64_t) aSig )<<29 ); - -} - /*---------------------------------------------------------------------------- | Returns the result of converting the single-precision floating-point value | `a' to the extended double-precision floating-point format. The conversion @@ -3677,173 +3749,6 @@ int float32_unordered_quiet(float32 a, float32 b, float_status *status) return 0; } - -/*---------------------------------------------------------------------------- -| Returns the result of converting the double-precision floating-point value -| `a' to the single-precision floating-point format. The conversion is -| performed according to the IEC/IEEE Standard for Binary Floating-Point -| Arithmetic. -*----------------------------------------------------------------------------*/ - -float32 float64_to_float32(float64 a, float_status *status) -{ - flag aSign; - int aExp; - uint64_t aSig; - uint32_t zSig; - a = float64_squash_input_denormal(a, status); - - aSig = extractFloat64Frac( a ); - aExp = extractFloat64Exp( a ); - aSign = extractFloat64Sign( a ); - if ( aExp == 0x7FF ) { - if (aSig) { - return commonNaNToFloat32(float64ToCommonNaN(a, status), status); - } - return packFloat32( aSign, 0xFF, 0 ); - } - shift64RightJamming( aSig, 22, &aSig ); - zSig = aSig; - if ( aExp || zSig ) { - zSig |= 0x40000000; - aExp -= 0x381; - } - return roundAndPackFloat32(aSign, aExp, zSig, status); - -} - - -/*---------------------------------------------------------------------------- -| Packs the sign `zSign', exponent `zExp', and significand `zSig' into a -| half-precision floating-point value, returning the result. After being -| shifted into the proper positions, the three fields are simply added -| together to form the result. This means that any integer portion of `zSig' -| will be added into the exponent. Since a properly normalized significand -| will have an integer portion equal to 1, the `zExp' input should be 1 less -| than the desired result exponent whenever `zSig' is a complete, normalized -| significand. -*----------------------------------------------------------------------------*/ -static float16 packFloat16(flag zSign, int zExp, uint16_t zSig) -{ - return make_float16( - (((uint32_t)zSign) << 15) + (((uint32_t)zExp) << 10) + zSig); -} - -/*---------------------------------------------------------------------------- -| Takes an abstract floating-point value having sign `zSign', exponent `zExp', -| and significand `zSig', and returns the proper half-precision floating- -| point value corresponding to the abstract input. Ordinarily, the abstract -| value is simply rounded and packed into the half-precision format, with -| the inexact exception raised if the abstract input cannot be represented -| exactly. However, if the abstract value is too large, the overflow and -| inexact exceptions are raised and an infinity or maximal finite value is -| returned. If the abstract value is too small, the input value is rounded to -| a subnormal number, and the underflow and inexact exceptions are raised if -| the abstract input cannot be represented exactly as a subnormal half- -| precision floating-point number. -| The `ieee' flag indicates whether to use IEEE standard half precision, or -| ARM-style "alternative representation", which omits the NaN and Inf -| encodings in order to raise the maximum representable exponent by one. -| The input significand `zSig' has its binary point between bits 22 -| and 23, which is 13 bits to the left of the usual location. This shifted -| significand must be normalized or smaller. If `zSig' is not normalized, -| `zExp' must be 0; in that case, the result returned is a subnormal number, -| and it must not require rounding. In the usual case that `zSig' is -| normalized, `zExp' must be 1 less than the ``true'' floating-point exponent. -| Note the slightly odd position of the binary point in zSig compared with the -| other roundAndPackFloat functions. This should probably be fixed if we -| need to implement more float16 routines than just conversion. -| The handling of underflow and overflow follows the IEC/IEEE Standard for -| Binary Floating-Point Arithmetic. -*----------------------------------------------------------------------------*/ - -static float16 roundAndPackFloat16(flag zSign, int zExp, - uint32_t zSig, flag ieee, - float_status *status) -{ - int maxexp = ieee ? 29 : 30; - uint32_t mask; - uint32_t increment; - bool rounding_bumps_exp; - bool is_tiny = false; - - /* Calculate the mask of bits of the mantissa which are not - * representable in half-precision and will be lost. - */ - if (zExp < 1) { - /* Will be denormal in halfprec */ - mask = 0x00ffffff; - if (zExp >= -11) { - mask >>= 11 + zExp; - } - } else { - /* Normal number in halfprec */ - mask = 0x00001fff; - } - - switch (status->float_rounding_mode) { - case float_round_nearest_even: - increment = (mask + 1) >> 1; - if ((zSig & mask) == increment) { - increment = zSig & (increment << 1); - } - break; - case float_round_ties_away: - increment = (mask + 1) >> 1; - break; - case float_round_up: - increment = zSign ? 0 : mask; - break; - case float_round_down: - increment = zSign ? mask : 0; - break; - default: /* round_to_zero */ - increment = 0; - break; - } - - rounding_bumps_exp = (zSig + increment >= 0x01000000); - - if (zExp > maxexp || (zExp == maxexp && rounding_bumps_exp)) { - if (ieee) { - float_raise(float_flag_overflow | float_flag_inexact, status); - return packFloat16(zSign, 0x1f, 0); - } else { - float_raise(float_flag_invalid, status); - return packFloat16(zSign, 0x1f, 0x3ff); - } - } - - if (zExp < 0) { - /* Note that flush-to-zero does not affect half-precision results */ - is_tiny = - (status->float_detect_tininess == float_tininess_before_rounding) - || (zExp < -1) - || (!rounding_bumps_exp); - } - if (zSig & mask) { - float_raise(float_flag_inexact, status); - if (is_tiny) { - float_raise(float_flag_underflow, status); - } - } - - zSig += increment; - if (rounding_bumps_exp) { - zSig >>= 1; - zExp++; - } - - if (zExp < -10) { - return packFloat16(zSign, 0, 0); - } - if (zExp < 0) { - zSig >>= -zExp; - zExp = 0; - } - return packFloat16(zSign, zExp, zSig >> 13); -} - /*---------------------------------------------------------------------------- | 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. @@ -3859,163 +3764,6 @@ float16 float16_squash_input_denormal(float16 a, float_status *status) return a; } -static void normalizeFloat16Subnormal(uint32_t aSig, int *zExpPtr, - uint32_t *zSigPtr) -{ - int8_t shiftCount = countLeadingZeros32(aSig) - 21; - *zSigPtr = aSig << shiftCount; - *zExpPtr = 1 - shiftCount; -} - -/* Half precision floats come in two formats: standard IEEE and "ARM" format. - The latter gains extra exponent range by omitting the NaN/Inf encodings. */ - -float32 float16_to_float32(float16 a, flag ieee, float_status *status) -{ - flag aSign; - int aExp; - uint32_t aSig; - - aSign = extractFloat16Sign(a); - aExp = extractFloat16Exp(a); - aSig = extractFloat16Frac(a); - - if (aExp == 0x1f && ieee) { - if (aSig) { - return commonNaNToFloat32(float16ToCommonNaN(a, status), status); - } - return packFloat32(aSign, 0xff, 0); - } - if (aExp == 0) { - if (aSig == 0) { - return packFloat32(aSign, 0, 0); - } - - normalizeFloat16Subnormal(aSig, &aExp, &aSig); - aExp--; - } - return packFloat32( aSign, aExp + 0x70, aSig << 13); -} - -float16 float32_to_float16(float32 a, flag ieee, float_status *status) -{ - flag aSign; - int aExp; - uint32_t aSig; - - a = float32_squash_input_denormal(a, status); - - aSig = extractFloat32Frac( a ); - aExp = extractFloat32Exp( a ); - aSign = extractFloat32Sign( a ); - if ( aExp == 0xFF ) { - if (aSig) { - /* Input is a NaN */ - if (!ieee) { - float_raise(float_flag_invalid, status); - return packFloat16(aSign, 0, 0); - } - return commonNaNToFloat16( - float32ToCommonNaN(a, status), status); - } - /* Infinity */ - if (!ieee) { - float_raise(float_flag_invalid, status); - return packFloat16(aSign, 0x1f, 0x3ff); - } - return packFloat16(aSign, 0x1f, 0); - } - if (aExp == 0 && aSig == 0) { - return packFloat16(aSign, 0, 0); - } - /* Decimal point between bits 22 and 23. Note that we add the 1 bit - * even if the input is denormal; however this is harmless because - * the largest possible single-precision denormal is still smaller - * than the smallest representable half-precision denormal, and so we - * will end up ignoring aSig and returning via the "always return zero" - * codepath. - */ - aSig |= 0x00800000; - aExp -= 0x71; - - return roundAndPackFloat16(aSign, aExp, aSig, ieee, status); -} - -float64 float16_to_float64(float16 a, flag ieee, float_status *status) -{ - flag aSign; - int aExp; - uint32_t aSig; - - aSign = extractFloat16Sign(a); - aExp = extractFloat16Exp(a); - aSig = extractFloat16Frac(a); - - if (aExp == 0x1f && ieee) { - if (aSig) { - return commonNaNToFloat64( - float16ToCommonNaN(a, status), status); - } - return packFloat64(aSign, 0x7ff, 0); - } - if (aExp == 0) { - if (aSig == 0) { - return packFloat64(aSign, 0, 0); - } - - normalizeFloat16Subnormal(aSig, &aExp, &aSig); - aExp--; - } - return packFloat64(aSign, aExp + 0x3f0, ((uint64_t)aSig) << 42); -} - -float16 float64_to_float16(float64 a, flag ieee, float_status *status) -{ - flag aSign; - int aExp; - uint64_t aSig; - uint32_t zSig; - - a = float64_squash_input_denormal(a, status); - - aSig = extractFloat64Frac(a); - aExp = extractFloat64Exp(a); - aSign = extractFloat64Sign(a); - if (aExp == 0x7FF) { - if (aSig) { - /* Input is a NaN */ - if (!ieee) { - float_raise(float_flag_invalid, status); - return packFloat16(aSign, 0, 0); - } - return commonNaNToFloat16( - float64ToCommonNaN(a, status), status); - } - /* Infinity */ - if (!ieee) { - float_raise(float_flag_invalid, status); - return packFloat16(aSign, 0x1f, 0x3ff); - } - return packFloat16(aSign, 0x1f, 0); - } - shift64RightJamming(aSig, 29, &aSig); - zSig = aSig; - if (aExp == 0 && zSig == 0) { - return packFloat16(aSign, 0, 0); - } - /* Decimal point between bits 22 and 23. Note that we add the 1 bit - * even if the input is denormal; however this is harmless because - * the largest possible single-precision denormal is still smaller - * than the smallest representable half-precision denormal, and so we - * will end up ignoring aSig and returning via the "always return zero" - * codepath. - */ - zSig |= 0x00800000; - aExp -= 0x3F1; - - return roundAndPackFloat16(aSign, aExp, zSig, ieee, status); -} - /*---------------------------------------------------------------------------- | Returns the result of converting the double-precision floating-point value | `a' to the extended double-precision floating-point format. The conversion |