[Bug lto/61886] [4.8/4.9/4.10 Regression] LTO breaks fread with _FORTIFY_SOURCE=2

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=61886

--- Comment #4 from Richard Biener <rguenth at gcc dot gnu.org> ---
Fully preprocessed glibc fread stuff (reduced testcase drops main path
and a prototype for __fread_chk):

extern size_t __fread_chk (void *__restrict __ptr, size_t __ptrlen,
      size_t __size, size_t __n,
      FILE *__restrict __stream) __attribute__ ((__warn_unused_result__));
extern size_t __fread_alias (void *__restrict __ptr, size_t __size, size_t __n,
FILE *__restrict __stream) __asm__ ("" "fread")


            __attribute__ ((__warn_unused_result__));
extern size_t __fread_chk_warn (void *__restrict __ptr, size_t __ptrlen, size_t
__size, size_t __n, FILE *__restrict __stream) __asm__ ("" "__fread_chk")




     __attribute__ ((__warn_unused_result__)) __attribute__((__warning__
("fread called with bigger size * nmemb than length " "of destination
buffer")))
                                 ;

extern __inline __attribute__ ((__always_inline__)) __attribute__
((__gnu_inline__)) __attribute__ ((__artificial__)) __attribute__
((__warn_unused_result__)) size_t
fread (void *__restrict __ptr, size_t __size, size_t __n,
       FILE *__restrict __stream)
{
  if (__builtin_object_size (__ptr, 0) != (size_t) -1)
    {
      if (!__builtin_constant_p (__size)
   || !__builtin_constant_p (__n)
   || (__size | __n) >= (((size_t) 1) << (8 * sizeof (size_t) / 2)))
 return __fread_chk (__ptr, __builtin_object_size (__ptr, 0), __size, __n,
__stream);

      if (__size * __n > __builtin_object_size (__ptr, 0))
 return __fread_chk_warn (__ptr, __builtin_object_size (__ptr, 0), __size, __n,
__stream);
    }
  return __fread_alias (__ptr, __size, __n, __stream);
}