https://gcc.gnu.org/bugzilla/show_bug.cgi?id=90381
--- Comment #1 from Li Jia He <helijia at gcc dot gnu.org> ---
Thanks for pointing this out.
I used the following code:
struct foo1 {
int i:1;
};
int test1 (struct foo1 *x)
{
if (x->i == 0)
return 1;
else if (x->i == 1)
return 1;
return 0;
}
to dumped the pass output in front of phiopt1
on be machine:
test1 (struct foo1 * x)
{
unsigned char _1;
int _3;
signed char _6;
<bb 2> :
_1 = BIT_FIELD_REF <*x_5(D), 8, 0>;
_6 = (signed char) _1;
if (_6 >= 0)
goto <bb 3>; [INV]
else
goto <bb 4>; [INV]
<bb 3> :
// predicted unlikely by early return (on trees) predictor.
<bb 4> :
# _3 = PHI <1(3), 0(2)>
return _3;
}
but, on le machine:
test1 (struct foo1 * x)
{
unsigned char _1;
unsigned char _2;
int _3;
<bb 2> :
_1 = BIT_FIELD_REF <*x_5(D), 8, 0>;
_2 = _1 & 1;
if (_2 == 0)
goto <bb 3>; [INV]
else
goto <bb 4>; [INV]
<bb 3> :
// predicted unlikely by early return (on trees) predictor.
<bb 4> :
# _3 = PHI <1(3), 0(2)>
return _3;
}
‘’’
The difference is the comparison code in the if statement, however
two_value_replacement will only optimize for EQ_EXPR or NE_EXPR.
Can we limit this test case to the le machine ? Thanks.
