[Bug tree-optimization/113703] ivopts miscompiles loop

[kristerw at gcc dot gnu.org via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=113703

--- Comment #2 from Krister Walfridsson <kristerw at gcc dot gnu.org> ---
Here is a runtime testcase:

#include <sys/mman.h>
#include <unistd.h>
#include <stdint.h>

__attribute__((noipa))
void f1 (char *p, uintptr_t i, uintptr_t n)
{
  p += i;
  do
    {
      *p = '\0';
      p += 1;
      i++;
    }
  while (i < n);
}

int main()
{
  long pgsz = sysconf (_SC_PAGESIZE);
  void *p = mmap (NULL, pgsz * 2, PROT_READ|PROT_WRITE,
     MAP_ANONYMOUS|MAP_PRIVATE, 0, 0);
  if (p == MAP_FAILED)
    return 0;
  mprotect (p+pgsz, pgsz, PROT_NONE);
  uintptr_t n = -3 - (uintptr_t)p;
  f1 (p+2, -2, n);
  return 0;
}