https://gcc.gnu.org/bugzilla/show_bug.cgi?id=127601
Bug ID: 127601
Summary: wrong code at -O3 due to vectorizer
Product: gcc
Version: 17.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: tree-optimization
Assignee: unassigned at gcc dot gnu.org
Reporter: kyuwoncho18 at gmail dot com
Target Milestone: ---
### Reproducer
#include <stdio.h>
#include <sys/mman.h>
#define PG 4096
static long
rev (long *a, int n)
{
long s = 0;
for (int i = n - 1; i >= 0; i--)
s += a[4 * i] + a[4 * i + 1] + a[4 * i + 2];
return s;
}
int main (void)
{
unsigned char *p = mmap (0, 2 * PG, PROT_READ | PROT_WRITE,
MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
if (p == MAP_FAILED || mprotect (p + PG, PG, PROT_NONE))
{ printf ("setup failed\n"); return 2; }
int n = 9;
unsigned long ne = 4UL * (n - 1) + 3; /* 35 longs are touched */
long *a = (long *) (p + PG - ne * sizeof (long));
for (unsigned long i = 0; i < ne; i++)
a[i] = (long) (i * 3 + 1);
printf ("%ld\n", rev (a, n));
return 0;
}
Result:
O{0,1,2}: 1404
O3: SIGSEGV
https://gcc.godbolt.org/z/Ph56qMKvs
