On 2016.11.29 at 15:14 +0100, Jakub Jelinek wrote:
> On Tue, Nov 29, 2016 at 03:08:15PM +0100, Markus Trippelsdorf wrote:
> > Building gcc with -fsanitize=undefined shows:
> > rtlanal.c:5210:38: runtime error: shift exponent 4294967295 is too
> > large for 64-bit type 'long unsigned int'
> >
> > 5210 return nonzero & (HOST_WIDE_INT_1U << (bitwidth - 1))
> > 5211 ? 1 : bitwidth - floor_log2 (nonzero) - 1;
> >
> > Here (bitwidth - 1) wraps around because bitwidth is zero and unsigned.
>
> Which modes have precision of 0? I'd expect just VOIDmode and BLKmode, any
> others? And for those I'd say it is a bug to call num_sign_bit_copies*.
Yes, only VOIDmode and BLKmode:
233 const unsigned short mode_precision[NUM_MACHINE_MODES] =
234 {
235 0, /* VOID */
236 0, /* BLK */
--
Markus
