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[Bug tree-optimization/39100] New: [4.4 Regression] -fstrict-aliasing miscompilation
- From: "jakub at gcc dot gnu dot org" <gcc-bugzilla at gcc dot gnu dot org>
- To: gcc-bugs at gcc dot gnu dot org
- Date: 4 Feb 2009 18:59:55 -0000
- Subject: [Bug tree-optimization/39100] New: [4.4 Regression] -fstrict-aliasing miscompilation
- Reply-to: gcc-bugzilla at gcc dot gnu dot org
typedef struct E
{
int p;
struct E *n;
} *EP;
typedef struct C
{
EP x;
short cn, cp;
} *CP;
__attribute__((noinline)) CP
foo (CP h, EP x)
{
EP pl = 0, *pa = &pl;
EP nl = 0, *na = &nl;
EP n;
while (x)
{
n = x->n;
if ((x->p & 1) == 1)
{
h->cp++;
*pa = x;
pa = &((*pa)->n);
}
else
{
h->cn++;
*na = x;
na = &((*na)->n);
}
x = n;
}
*pa = nl;
*na = 0;
h->x = pl;
return h;
}
int
main (void)
{
struct C c = { 0, 0, 0 };
struct E e[2] = { { 0, &e[1] }, { 1, 0 } };
EP p;
foo (&c, &e[0]);
if (c.cn != 1 || c.cp != 1)
__builtin_abort ();
if (c.x != &e[1])
__builtin_abort ();
if (e[1].n != &e[0])
__builtin_abort ();
if (e[0].n)
__builtin_abort ();
return 0;
}
is miscompiled on x86_64-linux with -O2, works with -O2 -fno-strict-aliasing
and with 4.3.2. When miscompiled, the *na = 0 store is optimized away.
--
Summary: [4.4 Regression] -fstrict-aliasing miscompilation
Product: gcc
Version: 4.4.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: tree-optimization
AssignedTo: unassigned at gcc dot gnu dot org
ReportedBy: jakub at gcc dot gnu dot org
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=39100