https://gcc.gnu.org/bugzilla/show_bug.cgi?id=70800
--- Comment #9 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
(In reply to David Binderman from comment #6)
> (In reply to Eric Gallager from comment #5)
>
> > keeping bug open for the enhancement to -Wtautological-compare
>
> I tried out the code in comment 1 on recent gcc trunk
> and the problem seems to be fixed:
>
> Alphasrc $ ~/gcc/results/bin/g++ -c -g -O2 -Wall jan22a.cc
> jan22a.cc: In function ‘void f(int)’:
> jan22a.cc:6:24: warning: bitwise comparison always evaluates to false
> [-Wtautological-compare]
> 6 | if ((n & 0x30) == 1)
> | ~~~~~~~~~~ ^~ ~
> Alphasrc $
The warning started to show up in GCC 8 for the reduced testcase in comment #1.
But the reduced testcase is different from the original code so ...
This will be the one for the missing warning:
extern void g(int n);
void f( unsigned long x)
{
if (((x) & 0xFFFFul) > 999999ul)
g( x);
}
