diff options
Diffstat (limited to 'libgcc/config/avr')
| -rw-r--r-- | libgcc/config/avr/libf7/libf7.c | 20 |
1 files changed, 15 insertions, 5 deletions
diff --git a/libgcc/config/avr/libf7/libf7.c b/libgcc/config/avr/libf7/libf7.c index 375becb..6fae4fc 100644 --- a/libgcc/config/avr/libf7/libf7.c +++ b/libgcc/config/avr/libf7/libf7.c @@ -440,11 +440,21 @@ f7_double_t f7_get_double (const f7_t *aa) mant &= 0x00ffffffffffffff; - // FIXME: For subnormals, rounding is premature and should be - // done *after* the mantissa has been shifted into place - // (or the round value be shifted left accordingly). - // Round. - mant += 1u << (F7_MANT_BITS - (1 + DBL_DIG_MANT) - 1); + // PR115419: The least significant nibble tells how to round: + // Tie breaks are rounded to even (Banker's rounding). + uint8_t lsn = mant & 0xff; + lsn &= 0xf; + // The LSB of the outgoing double is at bit 3. + if (lsn & (1 << 3)) + ++lsn; + if (lsn > (1 << 2)) + { + // FIXME: For subnormals, rounding is premature and should be + // done *after* the mantissa has been shifted into place + // (or the round value be shifted left accordingly). + // Round. + mant += 1u << (F7_MANT_BITS - (1 + DBL_DIG_MANT) - 1); + } uint8_t dex; register uint64_t r18 __asm ("r18") = mant; |