gcc/testsuite/gcc.c-torture/execute/pr113787.c

void foo(int x, int y, int z, int d, int *buf)
{
  for(int i = z; i < y-z; ++i)
    for(int j = 0; j < d; ++j)
      /* buf[x(i+1) + j] = buf[x(i+1)-j-1] */
      buf[i*x+(x-z+j)] = buf[i*x+(x-z-1-j)];
}

void bar(int x, int y, int z, int d, int *buf)
{
  for(int i = 0; i < d; ++i)
    for(int j = z; j < x-z; ++j)
      /* buf[j+(y+i)*x] = buf[j+(y-1-i)*x] */
      buf[j+(y-z+i)*x] = buf[j+(y-z-1-i)*x];
}

__attribute__((noipa))
void baz(int x, int y, int d, int *buf)
{
  foo(x, y, 0, d, buf);
  bar(x, y, 0, d, buf);
}

int main(void)
{
  int a[] = { 1, 2, 3 };
  baz (1, 2, 1, a);
  /* foo does:
     buf[1] = buf[0];
     buf[2] = buf[1];

     bar does:
     buf[2] = buf[1]; (no-op)
     so we should have { 1, 1, 1 }.  */
  for (int i = 0; i < 3; i++)
    if (a[i] != 1)
      __builtin_abort ();
}