rh1948567-1.c:
void foo (char x[2]);

int
main ()
{
  char x[2];
#pragma GCC diagnostic ignored "-Wstringop-overflow"
  foo (x + 1);
}
rh1948567-2.c:
void
foo (char x[2])
{
  asm volatile ("" : : "r" (&x[0]) : "memory");
}
gcc -W -Wall -flto -o rh1948567{,-1.c,-2.c}
rh1948567-1.c: In function ‘main’:
rh1948567-1.c:8:3: warning: ‘foo’ accessing 2 bytes in a region of size 1 [-Wstringop-overflow=]
    8 |   foo (x + 1);
      |   ^
rh1948567-1.c:8:3: note: referencing argument 1 of type ‘char[2]’
rh1948567-2.c:2:1: note: in a call to function ‘foo’
    2 | foo (char x[2])
      | ^

Shouldn't the diagnostic pragma prevent the warning even in the LTO case?