Dear Niels,
> Sorry for being unclear, sub_ddmmss has six arguments, and the case I
> wanted to single out was
>
> sub_ddmmss(rh, rl, ah, al, bh, /*compile time constant*/0)
>
> > in MPFR we have 15 places where we call sub_ddmmss, among which 8 have bl=0:
>
> Those seem to have al == 0 (in above notation), which is a different
> case.
sorry I mixed al and bl. After looking at the MPFR code that hit the bug:
if (MPFR_UNLIKELY(_r < MPFR_LIMB_HIGHBIT)) \
_r = MPFR_LIMB_HIGHBIT; \
umul_ppmm (_h, _l, _r, _r); \
sub_ddmmss (_h, _l, _u, 0, _h, _l); \
I guess the compiler did optimize separately the _r < MPFR_LIMB_HIGHBIT
case, in which case it did deduce _r = MPFR_LIMB_HIGHBIT, thus _l=0
after umul_ppmm, and the special code for bl=0 was used in longlong.h.
Paul
_______________________________________________
gmp-bugs mailing list
[email protected]
https://gmplib.org/mailman/listinfo/gmp-bugs
