https://gcc.gnu.org/bugzilla/show_bug.cgi?id=101066
Bug ID: 101066
Summary: Wrong code after fixup_cfg3
Product: gcc
Version: 12.0
Status: UNCONFIRMED
Keywords: wrong-code
Severity: normal
Priority: P3
Component: c
Assignee: unassigned at gcc dot gnu.org
Reporter: stefansf at linux dot ibm.com
Target Milestone: ---
Target: s390*-*-*, x86_64-*-*
int a = 1, c, d, e;
int *b = &a;
static int g(int *h) {
c = *h;
return d;
}
static void f(int *h) {
e = *h;
*b = 0;
g(h);
}
int main() {
f(b);
printf("%d\n", c);
}
Running `gcc t.c -Os && ./a.out` results in printed 1 whereas 0 is expected.
This does not happen for -O[0,1,2,3] i.e. there 0 is printed.
Prior fixup_cfg3 the code looks good to me and afterwards the assignment to c
uses a cached/initial value of variable a which is wrong:
int main ()
{
int * b.0_1;
int c.1_2;
int _6;
int _7;
int * b.2_8;
int _10;
int _11;
<bb 2> [local count: 1073741824]:
b.0_1 = b;
_6 = *b.0_1;
_7 = _6;
e = _7;
b.2_8 = b;
*b.2_8 = 0;
_10 = _6;
c = _10;
_11 = d;
c.1_2 = c;
printf ("%d\n", c.1_2);
return 0;
}
Reproducible on IBM Z as well as x86_64 using commit 831589c227c.
