https://gcc.gnu.org/bugzilla/show_bug.cgi?id=110731
--- Comment #2 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
I think the problem is earlier.
If I divide the same values unsigned, while the representation of the wide_int
values
is the same, i.e.
val = {0, -18014398509481984}, len = 2, precision = 119
for x, when divmod_internal_2 is called, in the signed case it sees
x/4wx b_dividend
0x7fffffffc0b0: 0x00000000 0x00000000 0x00000000 0xffc00000
while in the unsigned one
x/4wx b_dividend
0x7fffffffc0b0: 0x00000000 0x00000000 0x00000000 0x00400000
and I think the latter is what should be used in both cases, divmod_internal_2
performs
unsigned division.
So, I think the right fix is:
--- gcc/wide-int.cc.jj 2023-06-12 15:47:22.461502821 +0200
+++ gcc/wide-int.cc 2023-07-19 09:52:40.241661869 +0200
@@ -1911,9 +1911,9 @@ wi::divmod_internal (HOST_WIDE_INT *quot
}
wi_unpack (b_dividend, dividend.get_val (), dividend.get_len (),
- dividend_blocks_needed, dividend_prec, sgn);
+ dividend_blocks_needed, dividend_prec, UNSIGNED);
wi_unpack (b_divisor, divisor.get_val (), divisor.get_len (),
- divisor_blocks_needed, divisor_prec, sgn);
+ divisor_blocks_needed, divisor_prec, UNSIGNED);
m = dividend_blocks_needed;
b_dividend[m] = 0;
because at this point we are after the
/* Make the divisor and dividend positive and remember what we
did. */
if (sgn == SIGNED)
{
if (wi::neg_p (dividend))
{
neg_dividend = -dividend;
dividend = neg_dividend;
dividend_neg = true;
}
if (wi::neg_p (divisor))
{
neg_divisor = -divisor;
divisor = neg_divisor;
divisor_neg = true;
}
}
hunk. Of course, this makes a difference only if either the dividend or
divisor are the smallest negative value of a type.
