https://gcc.gnu.org/bugzilla/show_bug.cgi?id=64992
Andrew Pinski <pinskia at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Assignee|unassigned at gcc dot gnu.org |pinskia at gcc dot
gnu.org
Status|NEW |ASSIGNED
--- Comment #8 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
The missed optimization is:
int f(int c)
{
unsigned t = c == 1;
t <<= 1;
return t == 0;
}
int f1(int c)
{
unsigned t = c == 1;
return ((int)t) <= 0;
}
That is (t << 1) == 0 should be convert into either:
(t & 0x7fffffff) or ((int)t) <= 0
Though the (semi more) general case is:
(for shift (lshift rshift)
(for eqne (eq ne)
(simplify
(eqne (shift @0 INTEGER_CST@1) integer_zerop@2)
(with
{
mask = ...
}
(eqne (bit_and @0 { mask; }) @2)))))
And then the mask bit_and neeq to gtle
And then the rest will just work
