/* This is a software floating point library which can be used
for targets without hardware floating point.
- Copyright (C) 1994, 1995, 1996, 1997, 1998, 2000, 2001, 2002, 2003
+ Copyright (C) 1994, 1995, 1996, 1997, 1998, 2000, 2001, 2002, 2003, 2004
Free Software Foundation, Inc.
This file is free software; you can redistribute it and/or modify it
#include "tconfig.h"
#include "coretypes.h"
#include "tm.h"
-#include "fp-bit.h"
+#include "config/fp-bit.h"
/* The following macros can be defined to change the behavior of this file:
FLOAT: Implement a `float', aka SFmode, fp library. If this is not
exp = EXPMAX;
if (src->class == CLASS_QNAN || 1)
{
+#ifdef QUIET_NAN_NEGATED
+ fraction |= QUIET_NAN - 1;
+#else
fraction |= QUIET_NAN;
+#endif
}
}
else if (isinf (src))
dst.bits.exp = exp;
dst.bits.sign = sign;
#else
+# if defined TFLOAT && defined HALFFRACBITS
+ {
+ halffractype high, low, unity;
+ int lowsign, lowexp;
+
+ unity = (halffractype) 1 << HALFFRACBITS;
+
+ /* 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
+ {
+ while (lowexp > 0 && low < unity)
+ {
+ low <<= 1;
+ lowexp--;
+ }
+
+ if (lowexp <= 0)
+ {
+ halffractype roundmsb, round;
+ int shift;
+
+ shift = 1 - lowexp;
+ roundmsb = (1 << (shift - 1));
+ round = low & ((roundmsb << 1) - 1);
+
+ low >>= shift;
+ lowexp = 0;
+
+ if (round > roundmsb || (round == roundmsb && (low & 1) == 1))
+ {
+ low++;
+ if (low == unity)
+ /* LOW rounds up to the smallest normal number. */
+ lowexp++;
+ }
+ }
+
+ low &= unity - 1;
+ low |= (halffractype) lowexp << HALFFRACBITS;
+ low |= (halffractype) lowsign << (HALFFRACBITS + EXPBITS);
+ }
+ dst.value_raw = ((fractype) high << HALFSHIFT) | low;
+ }
+# else
dst.value_raw = fraction & ((((fractype)1) << FRACBITS) - (fractype)1);
dst.value_raw |= ((fractype) (exp & ((1 << EXPBITS) - 1))) << FRACBITS;
dst.value_raw |= ((fractype) (sign & 1)) << (FRACBITS | EXPBITS);
+# endif
#endif
#if defined(FLOAT_WORD_ORDER_MISMATCH) && !defined(FLOAT)
exp = src->bits.exp;
sign = src->bits.sign;
#else
+# if defined TFLOAT && defined HALFFRACBITS
+ {
+ halffractype high, low;
+
+ high = src->value_raw >> HALFSHIFT;
+ low = src->value_raw & (((fractype)1 << HALFSHIFT) - 1);
+
+ fraction = high & ((((fractype)1) << HALFFRACBITS) - 1);
+ fraction <<= FRACBITS - HALFFRACBITS;
+ exp = ((int)(high >> HALFFRACBITS)) & ((1 << EXPBITS) - 1);
+ sign = ((int)(high >> (((HALFFRACBITS + EXPBITS))))) & 1;
+
+ if (exp != EXPMAX && exp != 0 && low != 0)
+ {
+ int lowexp = ((int)(low >> HALFFRACBITS)) & ((1 << EXPBITS) - 1);
+ int lowsign = ((int)(low >> (((HALFFRACBITS + EXPBITS))))) & 1;
+ int shift;
+ fractype xlow;
+
+ xlow = low & ((((fractype)1) << HALFFRACBITS) - 1);
+ if (lowexp)
+ xlow |= (((halffractype)1) << HALFFRACBITS);
+ else
+ lowexp = 1;
+ shift = (FRACBITS - HALFFRACBITS) - (exp - lowexp);
+ if (shift > 0)
+ xlow <<= shift;
+ else if (shift < 0)
+ xlow >>= -shift;
+ if (sign == lowsign)
+ fraction += xlow;
+ 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
fraction = src->value_raw & ((((fractype)1) << FRACBITS) - 1);
exp = ((int)(src->value_raw >> FRACBITS)) & ((1 << EXPBITS) - 1);
sign = ((int)(src->value_raw >> (FRACBITS + EXPBITS))) & 1;
+# endif
#endif
dst->sign = sign;
else
{
/* Nonzero fraction, means nan */
+#ifdef QUIET_NAN_NEGATED
+ if ((fraction & QUIET_NAN) == 0)
+#else
if (fraction & QUIET_NAN)
+#endif
{
dst->class = CLASS_QNAN;
}
high |= 1;
low <<= 1;
}
- /* rounding is tricky. if we only round if it won't make us round later. */
-#if 0
- if (low & FRACHIGH2)
- {
- if (((high & GARDMASK) != GARDMSB)
- && (((high + 1) & GARDMASK) == GARDMSB))
- {
- /* don't round, it gets done again later. */
- }
- else
- {
- high++;
- }
- }
-#endif
+
if (!ROUND_TOWARDS_ZERO && (high & GARDMASK) == GARDMSB)
{
if (high & (1 << NGARDS))
{
- /* half way, so round to even */
- high += GARDROUND + 1;
+ /* Because we're half way, we would round to even by adding
+ GARDROUND + 1, except that's also done in the packing
+ function, and rounding twice will lose precision and cause
+ the result to be too far off. Example: 32-bit floats with
+ bit patterns 0xfff * 0x3f800400 ~= 0xfff (less than 0.5ulp
+ off), not 0x1000 (more than 0.5ulp off). */
}
else if (low)
{
- /* but we really weren't half way */
+ /* We're a further than half way by a small amount corresponding
+ to the bits set in "low". Knowing that, we round here and
+ not in pack_d, because there we don't have "low" available
+ anymore. */
high += GARDROUND + 1;
+
+ /* Avoid further rounding in pack_d. */
+ high &= ~(fractype) GARDMASK;
}
}
tmp->fraction.ll = high;
{
if (quotient & (1 << NGARDS))
{
- /* half way, so round to even */
- quotient += GARDROUND + 1;
+ /* Because we're half way, we would round to even by adding
+ GARDROUND + 1, except that's also done in the packing
+ function, and rounding twice will lose precision and cause
+ the result to be too far off. */
}
else if (numerator)
{
- /* but we really weren't half way, more bits exist */
+ /* We're a further than half way by the small amount
+ corresponding to the bits set in "numerator". Knowing
+ that, we round here and not in pack_d, because there we
+ don't have "numerator" available anymore. */
quotient += GARDROUND + 1;
+
+ /* Avoid further rounding in pack_d. */
+ quotient &= ~(fractype) GARDMASK;
}
}