------- Comment #3 from rguenth at gcc dot gnu dot org 2009-10-11 11:56 -------
The key is IMHO that the inner loop does not have its loop header copied.
This confuses SCEV enough to think that a = (unsigned short)a is always
executed. LIM is necessary to promote all the memory to SSA names, the
interesting CHREC that gets wrong is
<bb 3>:
..
a_lsm.6_18 = 0x0fffffff3;
goto <bb 5>;
<bb 4>:
...
a.1_2 = a_lsm.6_15;
D.2006_3 = (short unsigned int) a.1_2;
a.2_4 = (unsigned int) D.2006_3;
a_lsm.6_20 = a.2_4;
<bb 5>:
# a_lsm.6_15 = PHI <a_lsm.6_18(3), a_lsm.6_20(4)>
...
a.1_1 = a_lsm.6_15;
if (a.1_1 == 0)
goto <bb 4>;
else
goto <bb 6>;
<bb 6>:
...
- # a_lsm.6_27 = PHI <a_lsm.6_15(5)>
<bb 8>:
- # a_lsm.6_28 = PHI <a_lsm.6_27(6)>
- a = a_lsm.6_28;
+ a = 65523;
where interestingly a_lsm.6_15 isn't computed wrong.
Testcase, fails at -Os:
extern void abort (void);
unsigned int a;
int b, c;
void
foo (void)
{
b = 0;
do {
for (a = -13; a == 0; a = (unsigned short)a)
c = 1;
b++;
} while (b == 0);
}
int
main ()
{
foo ();
if (a != -13)
abort ();
return 0;
}
--
rguenth at gcc dot gnu dot org changed:
What |Removed |Added
----------------------------------------------------------------------------
CC| |spop at gcc dot gnu dot org
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=41497
