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Fix conversion of negative integer to real. 

When an integer/bool value is constant and negative,
and is used in a real-valued context, fix the
code generator calculation of the negative value.
This commit is contained in:
Stephen Williams 2008-09-19 17:04:40 -07:00
parent 2d1e0b3ade
commit 38e62bb1d2
1 changed files with 24 additions and 14 deletions
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38
tgt-vvp/eval_real.c
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@ -168,10 +168,30 @@ static int draw_number_real(ivl_expr_t exp)
unsigned long mant = 0, mask = -1UL;
int vexp = 0x1000;
/* If this is a negative number, then arrange for the 2's
complement to be calculated as we scan through the
value. Real values are sign-magnitude, and this negation
gets us a magnitide. */
int negate = 0;
int carry = 0;
if (ivl_expr_signed(exp) && (bits[wid-1] == '1')) {
negate = 1;
carry = 1;
}
for (idx = 0 ; idx < wid && idx < 8*sizeof(mant) ; idx += 1) {
mask <<= 1;
if (bits[idx] == '1')
mant |= 1 << idx;
int cur_bit = bits[idx] == '1'? 1 : 0;
if (negate) {
cur_bit ^= 1;
cur_bit += carry;
carry = (cur_bit >> 1) & 1;
cur_bit &= 1;
}
if (cur_bit) mant |= 1 << idx;
}
for ( ; idx < wid ; idx += 1) {
@ -185,19 +205,9 @@ static int draw_number_real(ivl_expr_t exp)
assert(0);
}
/* If this is actually a negative number, then get the
positive equivalent, and set the sign bit in the exponent
field.
To get the positive equivalent of mant we need to take the
negative of the mantissa (0-mant) but also be aware that
the bits may not have been as many bits as the width of the
mant variable. This would lead to spurious '1' bits in the
high bits of mant that are masked by ~((-1UL)<<wid). */
if (ivl_expr_signed(exp) && (bits[wid-1] == '1')) {
mant = (0-mant) & ~(mask);
/* If required, add in a sign bit. */
if (negate)
vexp |= 0x4000;
}
fprintf(vvp_out, " %%loadi/wr %d, %lu, %d; load(num)= %c%lu (wid=%u)\n",
res, mant, vexp, (vexp&0x4000)? '-' : '+', mant, wid);