https://gcc.gnu.org/bugzilla/show_bug.cgi?id=113588
Bug ID: 113588
Summary: The vectorizer is introducing out-of-bounds memory
access
Product: gcc
Version: 14.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: tree-optimization
Assignee: unassigned at gcc dot gnu.org
Reporter: kristerw at gcc dot gnu.org
Target Milestone: ---
The following function is miscompiled for x86_64 when compiled with
-O3 -march=x86-64-v2
unsigned long
foo (const char *s, unsigned long n)
{
unsigned long len = 0;
while (*s++ && n--)
++len;
return len;
}
The original function reads two bytes from 's' when called as:
char a[4];
a[0] = 1;
a[1] = 0;
foo(a, 1000);
However, the vectorized function reads 16 bytes (thereby accessing the buffer
out of bounds) as it reads one vector at a time when s[0] != 0 and n >= 16.
