diff options
| -rw-r--r-- | fpu/softfloat.c | 105 |
1 files changed, 66 insertions, 39 deletions
diff --git a/fpu/softfloat.c b/fpu/softfloat.c index dbda61bc8e..6a6b6567d7 100644 --- a/fpu/softfloat.c +++ b/fpu/softfloat.c @@ -3046,6 +3046,10 @@ float16 float32_to_float16(float32 a, flag ieee STATUS_PARAM) uint32_t mask; uint32_t increment; int8 roundingMode; + int maxexp = ieee ? 15 : 16; + bool rounding_bumps_exp; + bool is_tiny = false; + a = float32_squash_input_denormal(a STATUS_VAR); aSig = extractFloat32Frac( a ); @@ -3054,11 +3058,12 @@ float16 float32_to_float16(float32 a, flag ieee STATUS_PARAM) if ( aExp == 0xFF ) { if (aSig) { /* Input is a NaN */ - float16 r = commonNaNToFloat16( float32ToCommonNaN( a STATUS_VAR ) STATUS_VAR ); if (!ieee) { + float_raise(float_flag_invalid STATUS_VAR); return packFloat16(aSign, 0, 0); } - return r; + return commonNaNToFloat16( + float32ToCommonNaN(a STATUS_VAR) STATUS_VAR); } /* Infinity */ if (!ieee) { @@ -3070,58 +3075,80 @@ float16 float32_to_float16(float32 a, flag ieee STATUS_PARAM) if (aExp == 0 && aSig == 0) { return packFloat16(aSign, 0, 0); } - /* Decimal point between bits 22 and 23. */ + /* 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 -= 0x7f; + /* Calculate the mask of bits of the mantissa which are not + * representable in half-precision and will be lost. + */ if (aExp < -14) { + /* Will be denormal in halfprec */ mask = 0x00ffffff; if (aExp >= -24) { mask >>= 25 + aExp; } } else { + /* Normal number in halfprec */ mask = 0x00001fff; } - if (aSig & mask) { - float_raise( float_flag_underflow STATUS_VAR ); - roundingMode = STATUS(float_rounding_mode); - switch (roundingMode) { - case float_round_nearest_even: - increment = (mask + 1) >> 1; - if ((aSig & mask) == increment) { - increment = aSig & (increment << 1); - } - break; - case float_round_up: - increment = aSign ? 0 : mask; - break; - case float_round_down: - increment = aSign ? mask : 0; - break; - default: /* round_to_zero */ - increment = 0; - break; - } - aSig += increment; - if (aSig >= 0x01000000) { - aSig >>= 1; - aExp++; - } - } else if (aExp < -14 - && STATUS(float_detect_tininess) == float_tininess_before_rounding) { - float_raise( float_flag_underflow STATUS_VAR); - } - if (ieee) { - if (aExp > 15) { - float_raise( float_flag_overflow | float_flag_inexact STATUS_VAR); + roundingMode = STATUS(float_rounding_mode); + switch (roundingMode) { + case float_round_nearest_even: + increment = (mask + 1) >> 1; + if ((aSig & mask) == increment) { + increment = aSig & (increment << 1); + } + break; + case float_round_up: + increment = aSign ? 0 : mask; + break; + case float_round_down: + increment = aSign ? mask : 0; + break; + default: /* round_to_zero */ + increment = 0; + break; + } + + rounding_bumps_exp = (aSig + increment >= 0x01000000); + + if (aExp > maxexp || (aExp == maxexp && rounding_bumps_exp)) { + if (ieee) { + float_raise(float_flag_overflow | float_flag_inexact STATUS_VAR); return packFloat16(aSign, 0x1f, 0); - } - } else { - if (aExp > 16) { - float_raise(float_flag_invalid | float_flag_inexact STATUS_VAR); + } else { + float_raise(float_flag_invalid STATUS_VAR); return packFloat16(aSign, 0x1f, 0x3ff); } } + + if (aExp < -14) { + /* Note that flush-to-zero does not affect half-precision results */ + is_tiny = + (STATUS(float_detect_tininess) == float_tininess_before_rounding) + || (aExp < -15) + || (!rounding_bumps_exp); + } + if (aSig & mask) { + float_raise(float_flag_inexact STATUS_VAR); + if (is_tiny) { + float_raise(float_flag_underflow STATUS_VAR); + } + } + + aSig += increment; + if (rounding_bumps_exp) { + aSig >>= 1; + aExp++; + } + if (aExp < -24) { return packFloat16(aSign, 0, 0); } |