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fp-bit.c (pack_d): When using paired doubles to implement a long double...

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* config/fp-bit.c (pack_d): When using paired doubles to implement
	a long double, round the high part separately.
	(unpack_d): Fix the case in which the high part is a power of two
	and the low part is a nonzero value of the opposite sign.

From-SVN: r76780
This commit is contained in:
Richard Sandiford 2004-01-28 07:21:21 +00:00 • committed by Richard Sandiford
parent 28b241764f
commit faceece35d
2 changed files with 63 additions and 30 deletions
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7
gcc/ChangeLog
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@ -1,3 +1,10 @@
2004-01-28 Richard Sandiford <rsandifo@redhat.com>
* config/fp-bit.c (pack_d): When using paired doubles to implement
a long double, round the high part separately.
(unpack_d): Fix the case in which the high part is a power of two
and the low part is a nonzero value of the opposite sign.
2004-01-28 Kazu Hirata <kazu@cs.umass.edu>
* config/c4x/c4x.c (TARGET_ASM_EXTERNAL_LIBCALL): New.

86
gcc/config/fp-bit.c
View file

@ -330,58 +330,76 @@ pack_d ( fp_number_type * src)
#else
# if defined TFLOAT && defined HALFFRACBITS
{
halffractype high, low;
halffractype high, low, unity;
int lowsign, lowexp;
high = (fraction >> (FRACBITS - HALFFRACBITS));
high &= (((fractype)1) << HALFFRACBITS) - 1;
high |= ((fractype) (exp & ((1 << EXPBITS) - 1))) << HALFFRACBITS;
high |= ((fractype) (sign & 1)) << (HALFFRACBITS | EXPBITS);
unity = (halffractype) 1 << HALFFRACBITS;
low = (halffractype)fraction &
((((halffractype)1) << (FRACBITS - HALFFRACBITS)) - 1);
/* Set HIGH to the high double's significand, masking out the implicit 1.
Set LOW to the low double's full significand. */
high = (fraction >> (FRACBITS - HALFFRACBITS)) & (unity - 1);
low = fraction & (unity * 2 - 1);
/* Get the initial sign and exponent of the low double. */
lowexp = exp - HALFFRACBITS - 1;
lowsign = sign;
/* HIGH should be rounded like a normal double, making |LOW| <=
0.5 ULP of HIGH. Assume round-to-nearest. */
if (exp < EXPMAX)
if (low > unity || (low == unity && (high & 1) == 1))
{
/* Round HIGH up and adjust LOW to match. */
high++;
if (high == unity)
{
/* May make it infinite, but that's OK. */
high = 0;
exp++;
}
low = unity * 2 - low;
lowsign ^= 1;
}
high |= (halffractype) exp << HALFFRACBITS;
high |= (halffractype) sign << (HALFFRACBITS + EXPBITS);
if (exp == EXPMAX || exp == 0 || low == 0)
low = 0;
else
{
exp -= HALFFRACBITS + 1;
while (exp > 0
&& low < ((halffractype)1 << HALFFRACBITS))
while (lowexp > 0 && low < unity)
{
low <<= 1;
exp--;
lowexp--;
}
if (exp <= 0)
if (lowexp <= 0)
{
halffractype roundmsb, round;
int shift;
exp = -exp + 1;
roundmsb = (1 << (exp - 1));
shift = 1 - lowexp;
roundmsb = (1 << (shift - 1));
round = low & ((roundmsb << 1) - 1);
low >>= exp;
exp = 0;
low >>= shift;
lowexp = 0;
if (round > roundmsb || (round == roundmsb && (low & 1)))
if (round > roundmsb || (round == roundmsb && (low & 1) == 1))
{
low++;
if (low >= ((halffractype)1 << HALFFRACBITS))
/* We don't shift left, since it has just become the
smallest normal number, whose implicit 1 bit is
now indicated by the nonzero exponent. */
exp++;
if (low == unity)
/* LOW rounds up to the smallest normal number. */
lowexp++;
}
}
low &= ((halffractype)1 << HALFFRACBITS) - 1;
low |= ((fractype) (exp & ((1 << EXPBITS) - 1))) << HALFFRACBITS;
low |= ((fractype) (sign & 1)) << (HALFFRACBITS | EXPBITS);
low &= unity - 1;
low |= (halffractype) lowexp << HALFFRACBITS;
low |= (halffractype) lowsign << (HALFFRACBITS + EXPBITS);
}
dst.value_raw = (((fractype) high) << HALFSHIFT) | low;
dst.value_raw = ((fractype) high << HALFSHIFT) | low;
}
# else
dst.value_raw = fraction & ((((fractype)1) << FRACBITS) - (fractype)1);
@ -475,8 +493,16 @@ unpack_d (FLO_union_type * src, fp_number_type * dst)
xlow >>= -shift;
if (sign == lowsign)
fraction += xlow;
else
else if (fraction >= xlow)
fraction -= xlow;
else
{
/* The high part is a power of two but the full number is lower.
This code will leave the implicit 1 in FRACTION, but we'd
have added that below anyway. */
fraction = (((fractype) 1 << FRACBITS) - xlow) << 1;
exp--;
}
}
}
# else